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American Hand Book of the Daguerreotype by Samuel D. Humphrey

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and dried in the dark, and kept free from light and air.

CYANIDE OF POTASSIUM.

Cyanide of Potassium.--This important article is worthy
the undivided attention of every Daguerreotypist.
I here give Mr. Smee's process for its preparation.
This is from that author's work entitled, "Electro Metallurgy,"
American edition:

"The cyanide of potassium, so often alluded to while treating
of the metallo-cyanides, may be formed in several ways.
It may be obtained by heating to a dull redness the yellow ferrocyanate
of potash, in a covered vessel, filtering and rapidly evaporating it.
The objection to this method, however, is that without great care
the whole of the ferrocyanate is not decomposed, a circumstance
which much reduces its value for electro-metallurgy. By boiling,
however, the ignited residue with spirits of wine this difficulty
is said to be overcome, as the ferrocyanate is absolutely insoluble
in that menstruum, while the cyanuret, at that heat, freely dissolves,
and is as easily re-deposited on cooling.

"There is, however, a much better process by which this salt may
be formed, viz. by simply transmitting hydrocyanic acid through potassium.
Although the modes of making this acid are very numerous, there is but
one which is likely to be employed on a very large scale, and that is
its formation from the yellow ferrocyanate by means of sulphuric acid.
This process is performed as follows: any given weight of the yellow
salt is taken and dissolved in about five times its weight of water;
this is placed in a retort, or some such analogous vessel, to which is
then added a quantity of strong sulphuric acid, twice the weight of
the salt, and diluted with three or four times its quantity of water.
A pipe is carried from the neck of the retort to the receiving bottle,
which should be kept as cool as possible.

"For small operations, those invaluable vessels, Florence flasks,
answer well: a bent tube being connected at one end to its month,
the other passing into the second vessel; heat should be cautiously
applied by means of an Argand lamp, a little vessel of sand being
placed under the flask, which helps the acid to decompose the salt.
Prussic acid is then generated and passes through the tube to
the recipient vessel, which is to be charged with liquor potassae.

"When the potash is saturated, the operation is completed.
The Germans recommend a strong, alcoholic solution of potassa
to be used in the second vessel, for in this case, the hydrocyanic
or prussic acid combines with the potassa, forming a hydrocyanate
of potassa, or, the water being abstracted, the cyanuret
of potassium, which spontaneously precipitates, on the saturation
of the fluid, the cyanuret, being insoluble in strong alcohol.
The ferrocyanate of potash may be considered as containing
three equivalents of hydrocyanic acid, two of potash and one
of iron; but, unfortunately, we can only obtain half the acid
from the salt, owing to the formation of a compound during
its decomposition which resists the action of the acid.
The decomposition of this salt taking 2 equivalents or 426 grains
(to avoid fractions) would afford 3 equivalents or 81 grains
of hydrocyanic, or prussic acid, capable of forming 198 grains
of cyanuret of potassium, while in the retort there would
remain 384 grains or 3 equivalents of bisulphate of potash,
and 1 equivalent or 174 grains of a peculiar compound,
said to contain 3 equivalents of cyanogen, 1 of potassium,
and one of iron (Pereira). It is manifest that, but for this
later compound, we might double the quantity of hydrocyanic
acid from the yellow salt."

The decomposition just described is the one usually received;
but too much reliance must not be placed on its accuracy,
for the analysis of the several compounds is too difficult
for the results to be fully admitted. The residue left in
the retort speedily turns to one of the blues, identical with,
or allied to, Prussian blue. This is at best a disagreeable
process to conduct, for the hydrocyanic acid formed
adheres so strongly to the glass, that, instead of being
freely given off, bubbles are evolved suddenly with such
explosive violence as occasionally to crack the vessel.
This may be remedied as far as possible by the insertion
of plenty of waste pieces of platinum--if platinized,
so much the better, as that facilitates the escape of the gas.
The heat should be applied to every part of the vessel, and the flame
should not be allowed to play upon one single part alone.
Large commercial operations are performed in green glass
or stone-ware retorts.

"Now for one word of advice to the tyro: Remember that you are working
with prussic acid; therefore, never conduct the process in a room,
the fumes being quite as poisonous as the solution of the acid itself;
moreover, have always a bottle of ammonia or chlorine by your side,
that should you have chanced to inhale more than is pleasant,
it will be instantly at hand to counteract any bad effects.
It is stated by Pereira, that a little sulphuric acid or hydroferrocyanic
acid passes to the outer vessel, but probably the amount would be of no
consequence for electro-metallurgy, otherwise, it might be as well to use
a Woulfe's apparatus, and discard the salt formed in the first vessel.
To the large manufacturer it may be worth considering whether some other
metallo-cyanuret, formed in a similar manner to the ferrocyanuret,
might not be more advantageously employed, because the residue
of the process last described contains a large quantity of cyanogen
which the acid is unable to set free.

"There are other modes of procuring prussic acid, besides the one which has
been so tediously described; but these are found to be more expensive.
The only one which I shall now notice is the process by which it is
obtained from bicyanide of mercury. The bicyanide of mercury itself
is formed when peroxide of mercury is digested with Prussian blue,
the peroxide of mercury abstracting the whole of the cyanogen from
the blue, and leaving the oxides of iron at the bottom of the vessel.
The solution may be evaporated to dryness, and one part of the salt
dissolved in six of water; one part of muriatic acid, sp. gr. 1.15, is
then added, and the solution distilled, when the whole of the hydrocyanic
acid passes over, and by being conducted into a solution of potassa,
as in the former process, forms cyanuret of potassium. This process,
though easier than the first described, is rather given as a resource under
peculiar circumstances than as one to be adopted by the large manufacturer.
The expense is the only objection, but in a small quantity this cannot
be a consideration.

"In giving this very rough outline of the general mode of forming salts,
the minutiae necessary for chemical work have altogether been avoided,
and those parts alone are entered upon which are more immediately
necessary for the electro metallurgist to know and practice for himself.
This will account for the long description of the cyanuret of potassium,
while the preparation of the equally important and even more used acids,
the sulphuric, muriatic, etc., commonly found in commerce,
are altogether neglected.

"In using solutions of cyanide of potassium, the workman should not immerse
his arms into them, otherwise it occasionally happens that the solution
produces very troublesome eruptions over the skin."

HYPOSULPHITE OF SODA.

Hyposulphite of Soda.--This salt forms one of the important chemicals
for the Daguerreotype operator. Its application to this art is
of an interesting nature. It is used to dissolve the sensitive salt
of silver which remains unchanged during the exposure in the camera.
It has the property of readily dissolving the chloride, bromide and
iodide of silver. It should be pure and free from sulphuret of sodium;
should this last be present, it will cause brown spots of sulphurated
silver upon the Daguerreotype impression. This annoyance is a
great source of complaint from many operators, and ever will be,
so long as it is prepared by men who have no reputation to lose,
and whose eyes are blinded by the "Almighty Dollar."

A good article may be prepared as follows:

"Mix one pound of finely pulverized carbonate of soda with ten ounces
of flowers of sulphur, and heat the mixture slowly in a porcelain dish till
the sulphur melts. Stir the fused mass, so as to expose all its parts
freely to the atmosphere, whereby it passes from the state of a sulphuret,
by the absorption of atmospheric oxygen, into that of a sulphite,
with the phenomenon of very slight incandescence. Dissolve in water,
filter the solution, and boil it immediately along with flowers of sulphur.
The filtered concentrated saline liquid will afford, on cooling, a large
quantity of pure and beautiful crystals of hyposulphite of soda."

Hyposulphite of Gold.--This compound salt is by a few considered preferable
to the chloride of gold, but our experience has induced us to use the latter,
believing we are enabled to produce a more brilliant and warm-toned
impression with it. When the hyposulphite of gold is used in gilding,
it requires less heat and a longer application, as there is some danger
of producing a glossy scum over some parts of the surface of the plate.
I prepare this salt as follows:

Dissolve one part chloride of gold and four parts
hyposulphite of soda in equal quantities of distilled water:
pour the gold into the hyposulphite solution, in the same
manner as in mixing the gilding solution; let it stand
until it becomes limpid; filter and evaporate to dryness.
Re-dissolve and add a few grains of burnt alum.

After standing a few hours, filter and evaporate again. If not
sufficiently pure, repeat the crystallization until it is so.
For gilding, dissolve in water and use in the same manner
as the common gilding solution.

N.B.--The four following mixtures were employed in Neipce's
process in his earliest experiments:

Aqueous Solution of Bichloride of Mercury.--Eight grains of bichloride
of mercury in 10,000 grains of distilled water.

Solution of Cyanide of Mercury.--A flask of distilled water is
saturated with cyanide of mercury, and a certain quantity is decanted,
which is diluted with an equal quantity of distilled water.

Acidulated White Oil of Petroleum.--This oil is acidulated by mixing
with it one tenth of pure nitric acid, leaving it for at least 48 hours,
occasionally agitating the flask. The oil, which is acidulated,
and which then powerfully reddens litmus paper, is decanted.
It is also a little colored, but remains very limpid.

Solution of Chloride of Gold and Platinum.--In order not to
multiply the solutions, take the ordinary chloride of gold,
used for fixing the impressions, and which is composed of 1
gramme of chloride of gold and 50 grains of hyposulphate of soda,
to a quart of distilled water.

With respect to chloride of platinum, 4 grains must be dissolved in 3 quarts
of distilled water; these two solutions are mixed in equal quantities.

Acids.--I shall not go into the preparations of the various acids
employed in the Daguerreotype. This would be useless to the operator,
as there are few, if any, that it would be advisable to prepare.
It is only necessary for the experimenter to be made acquainted with
their properties, and this in order to prevent any haphazard experiments,
which are too common among operators. Any person who may be desirous
to try an experiment, should first study the agents he wishes to employ.
By so doing much time and money will be saved; while the searcher after
new discoveries would rarely become vexed on account of his own ignorance,
or be obliged to avail himself of the experience of others in any
department of science.

Nitric Acid--Exists in combination with the bases, potash, soda,
lime, magnesia, in both the mineral and vegetable kingdoms,
and is never found insoluble. It has the same constituents
as common air, but in different proportions. The strongest nitric
acid contains in every pound, two and a quarter ounces of water.
Pure nitric acid is colorless, with a specific gravity of 1.5,
and boiling at 248 deg.. It is a most powerful oxidizing agent,
and is decomposed with more or less rapidity, by almost all the metals,
to which it yields a portion of its oxygen.

The nitric acid of commerce, is generally the article used by
the Daguerreotypist. This usually contains some chlorine and sulphuric acid.
It is obtained by the distillation of saltpetre with sulphuric acid.
It is employed in the Daguerreotype process for dissolving silver,
preparing chloride or oxide, nitrate of silver, [the former used
in galvanizing,] and in combination with muriatic acid for preparing
chloride of gold, used in gilding. It is also used by some for
preparing the plate.

Acidulated Solution.--This solution is used for cleaning
the surface of the Daguerreotype plate. It has the property
of softening the silver, and bringing it to a state in which it
is very susceptible of being either oxidized or iodized,
hence it contributes to increase the sensibility of the plate.
The proportions are to one drop of acid add from 15 to 20
drops of water, or make the solution about like sharp vinegar
to the taste.

Nitro-Muriatic Acid.--Aqua Regia is a compound menstruum invented
by the alchemists for dissolving gold. It is composed of colorless
nitric acid (aqua-fortis) and ordinary muriatic acid; the mixture
is yellow, and acquires the power of dissolving gold and platinum.
These materials are not properly oxidized; it nearly causes their
combination with chlorine, which is in the Muriatic acid.

Hydrochloric Acid (Muriatic Acid).--This acid forms a valuable
addition to the chemicals employed by the practical Daguerreotypist.
This acid is formed by acting upon common salt (which is chloride
of sodium) by concentrated sulphuric acid. The water of the acid
is decomposed, and its hydrogen combines with the chloride of the salt
to form muriatic acid, and this unites with the sulphuric acid
to form sulphate of soda; 60 parts of common salt and 49 parts
of concentrated sulphuric acid, afford, by this mutual action,
37 parts of muriatic acid and 72 parts of sulphate of soda.
The muriatic acid of commerce has usually a yellowish tinge,
but when chemically pure it is colorless. The former is commonly
contaminated with sulphurous acid, sulphuric acid, chlorine, iron,
and sometimes with arsenic.

Muriatic acid, from the fact of the presence of the chlorine, is used
in the Daguerreotype process for dissolving gold, and in combination
with various accelerators. Its presence can be detected by ammonia.
A strip of paper dipped in this and waved to and fro will emit
a thick white smoke if the acid vapor be in the atmosphere.
The ammonia neutralizes the acid fumes. By reversing the experiment we
can determine whether vapor of ammonia be in the air, and also deprive
these suffocating and dangerous gases of their injurious properties,
and remove them from the air. Every Daguerreotype operator should
be furnished with, at least, a six ounce bottle of aqua ammonia.
Its operation is very nearly the same on bromine and iodine vapor.

Hydrofluoric Acid (Fluorohydric Acid).--This acid is used to form some of
the most volatile and sensitive compounds employed in the Daguerreotype.
It is one of the most dangerous bodies to experiment with:
it is volatile and corrosive, giving off dense white fumes
in the air. It combines with water with great heat. At 32 deg.
it condenses into a colorless fluid, with a density 1.069. It is
obtained from decomposition of fluorspar by strong sulphuric acid.
It readily dissolves the silica in glass, and consequently cannot be
kept in a vessel of that material. It is prepared and kept in lead.
It is employed in accelerators on account of its fluorine.

One small drop on the tongue of a dog causes death.
The operator who wishes to use it should pour some
of the liquid for which he intends it into a graduate,
or other vessel, and then add the desired quantity of acid.
If by accident any of the spray should fall upon the skin,
it should at once be copiously drenched with water.

Sulphuric Acid.--There are two sorts of this acid:
one is an oily, fuming liquid; this is made in Nordhausen,
in Saxony, and is commonly called "Nordhausen sulphuric acid,"
or oil of vitriol. The other which is the kind used in
connection with the Daguerreotype, is common sulphuric acid.
It is somewhat thinner, and when undiluted is not fuming.
This acid may be obtained in a solid and dry state,
called anhydrous sulphuric acid.

The common sulphuric acid is made by burning sulphur, which forms
sulphurous acid. To convert this into sulphuric acid and gain
more oxygen, nitric acid, which is rich in that body, is added.
It forms a limpid, colorless fluid, of a specific gravity
of 1.8. It boils at 620 deg.; it freezes at 15 deg.
It is acrid and caustic, and intensely acid in all its characters,
even when largely diluted.

Its attraction for basis is such that it separates or expels all
other acids, more or less perfectly, from their combinations.
Its affinity for water is such that it rapidly absorbs it from
the atmosphere, and when mixed with water much heat is evolved.
It acts energetically upon animal and vegetable substances,
and is a poisonous, dangerous substance to get on the skin.
It is a powerful oxidizing agent; hence its use in the galvanic battery,
for which purpose it is mostly used by the Daguerreotypist.
The fumes of this being so much more offensive than nitric acid,
the latter is sometimes used. It is also employed in some of
the more sensitive accelerators.

ACCELERATING SUBSTANCES.

Remarks on the Accelerating substances Used in the Daguerreotype.--
I have now arrived at a point in this work, where the eye of
the Daguerreotype public will intently search for something new.
This search will prove in vain, at least so far as regards
those who have enjoyed and embraced the opportunities for studying
the principles of our art. Every experienced operator has in a degree
become familiar with the mechanical uses of all the agents employed,
while I fear but few understand the properties, and laws governing
those properties, which are so indispensable to produce an image
impressed upon the silver surface.

There are three substances which form the bases for
producing a Daguerreotype; silver, iodine and bromine.
Each forms a separate body which is indispensable to the
operators success as the art is now practiced in America.
With these three, compounds of great variety are formed.

The silver surface is first thoroughly cleaned and freed from all organic
matter, then exposed to vapor of iodine, producing an iodide of silver.
The plate upon which is this salt, is again exposed to the vapor of bromine,
forming a bromo-iodide of silver, a salt also.

As most of the various accelerators are compounds of bromine, with either
chlorine or fluorine combination, they partake somewhat of the nature of these
latter, giving results which can be detected by the experienced operator.
Thus muriatic acid is added for its chlorine, which can generally be
detected by the impression produced, being of a light, soft, mellow tone,
and in most cases presenting a brilliant black to that colored drapery.
Those who wish to experiment with agents for accelerating substances,
should first study to well understand their peculiar nature and properties;
as well, also, to endeavor to find out what will be the probable changes
they undergo in combination as an accelerator. This should be done before
making the experiments. From the foregoing it will be seen that numerous
compounds are formed from the same basis, and, consequently, it would
be a waste of time and a useless appropriation to devote more of our space
than is necessary to give the principal and most reliable combination.

In America, the words "Quick" and "Quick Stuff," are more generally used for
and instead of the more proper names, "Sensitives," or "Accelerators," etc.
As it has by use become common, I frequently use it in this work.

Liquid Accelerator, No. 1.--This mixture was used by me in 1849,
and is given as it appeared in my "System of Photography,"
published at the above date:

Take pure rain or distilled water, one quart, filter through
paper into a ground stopper bottle, and add, for warm weather,
one and a half ounce chloride of iodine; or for cold,
one ounce; then add one ounce bromine, and shake well.
Now with care not to allow the vapor to escape, add drop by drop,
thirty drops of aqua ammonia, shaking well at each drop. Care must
be taken not to add more at a time, as it evokes too much heat.
This mixed, in equal proportions with John Roach's quick,
forms an excellent chemical combination. For this purpose,
take one and a half ounce of each, to which add ten ounces water,
for warm weather, or from six to seven for cold. Pour the whole
into a large box, and it will work from two to four months.
I am now using (l849) one charged as above which has been
in constant use for three months, and works uniformly well.
The above is right for half or full size boxes, but half of it
would be sufficient for a quarter size box.

Coat to the first shade of rose over iodine, change to a deep
rosy red over quick, and black about one tenth the first.

I would not now recommend the addition of "John Roach s quick,"
as I believe equally good results can be produced without it.
This liquid is now used by many, and is very good for taking views.

Lime Water Quick.--This mixture is more used at present than
all the other liquids ever introduced. It produced the most
uniform results, giving the fine soft tone so characteristic
in pictures produces from accelerators containing chlorine.
To one quart of lime water (this can be had of any druggist)
add one and a half ounce of pulverized alum.
This should be shook at intervals for twenty--four hours;
then add one ounce of chloride of iodine and three fourths
ounce of bromine.

Lime Water.--This is easily prepared by putting lime into water,
say a piece of quick-lime about the size of an egg into one quart of water.
This should be shook occasionally for two or three days and allowed to settle,
when the water can be poured off and used.

Use.--To one part of quick add six parts of water; coat to a light yellow
over the iodine, to a rose color over the quick, and recoat about one tenth.
The above coating may be increased or diminished, it matters not,
so that there is not too much, and the proper proportions are preserved.
Some add to the above a small quantity of magnesia, say about a teaspoonful
to the quart of liquid.

Liquid Accelerator, No. 2.--The following was for a long
time used by one of the first houses in the United States,
and probably was one of the first liquids ever used.
It produces a fine-toned picture, but is not considered as sure
as the lime water quick:

Take rain water one quart, add pulverized alum until it is a little sour
to the taste, and a small piece, say one half inch square, of magnesia.
Filter through paper, and add chloride of iodine one half ounce,
bromine sufficient to take it up, which is a little less than half an ounce.

Charge with one of quick to six of water; coat over iodine
to a soft yellow, nearly, but not quite, bordering on a rose;
over quick to a dark purple, or steel, and back one sixth
to one tenth.

Wolcott's American Mixture.--Van Loan Quick.--This mixture was first
formed and used by T. Wolcott & Johnson and gained great celebrity for
its productions. I have now a bottle hermetically sealed that contains
about a half ounce of this mixture prepared in 1841 by John Johnson,
now a resident of this city, and the former partner of Mr. Wolcott.
The preparation of this mixture, as furnished by Mr. Johnson himself,
is given as follows:

"One part of bromine, eight parts of nitric acid,
sixteen parts of muriatic acid, water one hundred parts.
This mixture should be allowed to stand for several days;
it improves by age.

"Use.--A few drops say, 6 to 12, of this mixture, should be put
into about 6 or 8 ounces of water; it will require frequent
replenishing by the addition of a few more drops. The plate should
be coated over the dry iodine to a red just bordering on a slate.
and then exposed to the mixture only sufficiently long to change the color.
If this is not done in less than six seconds it is not strong enough.
Re-coat over the iodine full one fourth as long as first coating."

This exceedingly volatile compound is difficult to control
from its instability; it is but little used. The impressions
successfully produced by this mixture are very brilliant,
and possess a pleasing peculiarity.

DRY SENSITIVES.

Hydrate of Lime.--The operation by which water is combined
with lime is called slaking. Take a piece of quick lime,
common lime used in mortar, and immerse it in warm water for
about fifteen seconds; then place it in an iron or tin vessel.
It will soon begin to swell, evolving a great deal of heat and
emitting steam, and soon falls into a fine powder, hydrate of lime.
This should be well stirred and allowed to cool, and then
bottled in order to prevent it from giving off the hydrate
and recovering the carbonic acid from the atmosphere.
The last is detrimental to its use with bromine, and is one
cause of the complaint that "it will not take bromine."
The hydrate of lime should, not be dried over a heat,
as has been supposed by many, for in that case
the hydrogen is expelled and it returns to a carbonate.
It is advisable to cool it in a damp place like a ground cellar.
Much of the lime in our market will not, except it be quite damp,
combine with the bromine. This is owing to impurities.
Nothing is equal to oyster-shell lime, which I use altogether.

Bromide of Lime.--In preparing large quantities of this, we adopt
the following method: Fill a four-quart bottle about two-thirds full
of hydrate of lime; pour into this about one or two ounces of bromine;
then shake well, add more of the bromine, shake well and let it stand
for a few hours, adding sufficient bromine to give it a fine red color.
It is better when kept in the large bottles, as it forms a more
perfect combination: in other words it improves by age.

Use.--Coat over the iodine to a rose red and then over this mixture
to a purple or slate; recoat over the first about one fourth as long
as first coating.

Gurneys American Compound.--Of this compound there are two combinations,
one for use, when the temperature of the atmosphere is above 65 or 70
deg., and the other at a lower temperature. The first is called No. 1,
the second No. 2.

No. 1 is prepared by placing hydrate of lime in a bottle,
say to three quarts of the hydrate of lime, add one ounce
of pulverized burnt alum, and as much chloride of lime as can
be put on a quarter of a dollar, and from l5 to 30 grains
of dry pulverized iodine, or enough to change the color of
the hydrate of lime, to the slightest possible tinge of yellow.
There had better be less than carry the color to a deeper shade.
The object of using the iodine is to form a compound with
bromine that is not so volatile as the bromine itself.
No matter how little iodine is combined with the bromine,
the vapors possess their relative proportion; hence, only enough
iodine to prevent "flaring," or as it is often termed
a "scum-coating," is used. The iodine should be thoroughly
combined with the lime, which will take about one or two days.
Should add bromine the same as in bromide of lime,
until the compound assumes a light red color.

No. 2 is prepared in the same manner as No. 1, except the addition
of the iodine, which is omitted.

Use.--No. 1. Coat over the iodine to a bright yellow color,
then over the compound, No. 1, to red color, recoat over iodine,
about one sixth as long, as the time occupied in first coating.

No. 2. Coat over iodine same as above, except recoat over the iodine
about one fourth to one half as long as first coating.

Dry Quick, No. 1.--Bromide of Lime and Starch.--The following
compound forms an excellent accelerator, and is used by many.
It is claimed for this preparation, that it will hold
the bromine longer than others where starch is not employed.
As regards this claim we do not think it can be substantiated.
Our experience in practice has led us to the conclusion
that there is no great difference as respects durability,
but there is some little difference as regards the tone
of the impressions produced by its use.

To one quart of hydrate of lime add one quart of finely pulverized starch.
To this mixture add bromine, until it assumes a deep yellow or pink color.

Starch may be added to any of the dry mixtures.

Use.--Coat over the iodine to a deep yellow, then over this quick
to a red color, recoat about one sixth of the time of first coating.

I will here again remark, that the exact color of the coating
is not essentially provided a proper proportion is preserved.

I have never seen it stated, though it be a fact worthy of note,
that a proportionate time for coating over the iodine and accelerator,
will not answer. For example: if a plate exposed to the vapor
of iodine be perfectly coated in sixteen seconds, and then
exposed to an accelerator, (not having iodine in its combination)
receives its coating in four seconds, it will be found that a proper
proportionate coating cannot be preserved by adopting, a proportion
of time, but on the contrary, the time will diminish; for exposure
over the accelerator, as in the above example, if it be desired to coat
the plate with twice as much iodine as in the above example, the time
would be, over iodine thirty-two seconds, and over the accelerator
(to possess a proper proportion) from six to seven seconds.
Hence it is that many inexperienced operators, when wishing to vary
their usual manner of coating, fail in producing a favorable result.
They coat calculating a proportion of time when they should not.

Dry Quick, No. 2.--Bromide of Lime and Magnesia.--To one quart of hydrate
of lime add one quart of magnesia, and mix them well together; add bromine
same as in preparing bromide of lime; coat the same as over dry quick No. 1.
This combination produces very uniform results, and is worked with much
success by beginners.

Chloro-Bromide of Lime.--To the bromide of lime add chloride of bromine
until the mixture becomes a pale yellow color, resembling sulphur.
It should be shook well, and enough of the chloride of bromine added
to bring the compound to a deep blood red color.

Use.--Coat over the iodine to a pink color, and then over the above to a red,
or just changing the color. It should be remembered that accelerators
containing chlorine do not admit of a great change of color of coating
on the plate.

Iodide of Starch.--This mixture can be employed for coating over in
warm weather, and prevent the flashing resulting at high temperatures.
It may be used the same as the iodide alone.

To six ounces of finely pulverized starch, add one fourth ounce
of dry iodine.

Use.--Same as the dry iodine alone.

The same combination may be made with lime, magnesia and other substances.

Concentrated Solution of Iodine for First Coating.--It may appear
strange to some of our old operators that an aqueous solution of iodine
can be used for coating the plate and forming the iodide of silver.
It has long been a cry among most operators that it is impossible to succeed
when the iodine box contains dampness. Now this is a great mistake,
and we will here state that in all cases where dampness appears
upon a properly prepared Daguerreotype plate, it is the result of a
different temperature of the metal from the air which surrounds it.
Mr. Senter, of Auburn, was the first of our operators who used a solution
of iodine for coating the plate, and we several years since saw
his results, which would rival the production of any other operator.
A concentrated solution of iodine is prepared by putting into a common
bottle two thimblesful of hyposulphite of soda and a rather larger
quantity of iodine, so that there may be more than sufficient.
Add to it about 40 ounces of common water (heated to 60 or 70 degrees),
by little and little, moving, the bottle to warm it, for fear of breaking.
After shaking it a short time, the water is rapidly and strongly colored.
The solution should be poured into a bottle with a ground stopper,
and when cool used for iodizing.

A solution of sufficient strength can be made by moistening
or just covering the iodine with water.

Chloride of Iodine as an Accelerator.--This is probably one of the best
accelerators that can be used for coating the plate for taking views;
it works too slow, however, to meet the wants of the operating room,
yet its use was formerly, for a long time, adhered to by some of our
best professors. In producing views with this, we are successful in
obtaining well-developed impressions, with a depth of tone and richness
of appearance not to be met with in the productions of any other substances.
I give its use as furnished me by an old and experienced operator,
and published in Humphrey's Journal, vol. i. p. 180:

"As the process of using chloride of iodine may be of interest to some
of our subscribers, I take pleasure in giving the following manipulation.
To one ounce of chloride of iodine add two ounces of water;
place this mixture in a coating-box, the same as quick stuff;
coat the plate with dry iodine to a light yellow, or lemon color;
then bring the coating to a deep pink over the chloride.
The plate must be recoated over the dry iodine."

This combination has been very successfully used in one of our
most extensive establishments in this city, and the superiority
of the pictures produced by it was considered as an equivalent
for the additional time required to bring out the impressions.

Chlorine as an Accelerator.--I shall here refer to but a single
experiment in which I employed chlorine gas for coating the plate.
I was provided with a retort, the neck of which was fitted to the jar
of my coating-box, through a hole drilled for its reception.
This was fitted perfectly tight in my coating-box. I placed
some pure undiluted bromine water and the agents necessary
for producing chlorine gas (in small quantity) in the retort.
The result was that my first experiment produced an impression
completely solarized in all its parts by an exposure of four seconds
of time, which would have required an exposure of twenty seconds
to produce a perfectly developed impression by the usual process.

Another trial immediately produced one of the finest toned impressions
I ever saw, perfectly developed in one second of time.

My next two or three experiments proved total failures.
I was unable to produce even a sign of an impression.
By accident my retort was broken, and not being in a
locality convenient to obtain another, my experiments
were necessarily suspended.

My attention was not called to this subject again for several years,
when I noticed an account of some similar experiments by F. A. P. Barnard
and Dr. W. H. Harrington, the latter of whom is now of the firm of Dobyns
& Harrington, of New Orleans.

From reading this article, I found my own difficulties explained.
Too much of the chlorine gas was present in my coating jar.
I would like to see some of our enterprising operators
investigate this combination.

It is a singular fact, that the vapors of bromine and chlorine combining
upon the iodide of silver, produce a more sensitive coating than when
the two are combined in solution, as in chloride of bromine solution.
Those having Humphrey's Journal at hand, can refer to vol. i. p. 142.

To use Bromine Water or other Accelerators in Hot Weather.--
An excellent plan for using bromine water is as follows:

Fill a two-ounce bottle quarter full of it, and then fill the bottle
with fine sand, which serves to preserve a low temperature;
then place the bottle in a porous cup, same as used in the battery;
fill this also with sand, and close the end with plaster of Paris.
Place this in a coating-box, and it will be found to act with great
uniformity and be quite permanent.

Bromide of Lime, another accelerator, can be used in the same manner,
except it is, only necessary, when a solid sensitive is used,
to mix it with the sand without placing it in a bottle.
This method is employed with great success by a few, who have
regarded it as a secret worth keeping.

A Combination, requiring the Use of only One Coating-box.--
It is often wondered by beginners, why some solution requiring only
one coating cannot be employed. This can be done, but the results
are not so satisfactory as when two or more are employed.
Such an accelerator may be produced by adding alcoholic
solution of iodine to a solution of chlorate of potash,
until the latter will take up no more of the former,
and to each ounce, by measure of this solution, ten drops
of a saturated solution of bromide in water are added.
The solution of chlorate of potash is made by diluting, one part
of a saturated solution of the salt with ten parts of water.
The use of the chlorate is simply as a solvent of iodine.

Fats as Accelerators.--The use of fats, oils, or greasy substances,
has been one of the most emphatic prohibitions about the
Daguerreotype plate. Yet it has been proved that its presence
in a small quantity upon the silver surface has the effect
of reducing the time of exposure in the camera from two-thirds
to three-fourths. An application may be made as follows:
Pour sweet oil, or rub beef or mutton fat, on a common buff,
which is free from all polishing powders. With this, buff a
well-cleaned plate, and it will leave a scum, which should be
mostly removed by using another buff, which should be clean.
Coat the plate in the usual manner, and the result will be
a great reduction in the time of exposure in the camera.
The impression produced upon a plate so prepared presents,
when coming from the vapor of mercury, a grey, scummy appearance,
which, on the application of heat in gilding, does not improve;
hence its use is not generally adopted.

We have instituted some investigations upon this subject,
and in the present volume, we shall not refer to it further.
Those wishing to learn more fully the effect of light upon
organic substances will find Robert Hunt's "Researches on Light"
an invaluable work.

LIGHT AND OPTICS.

CHAPTER IV.

Light--Optics--Solar Spectrum--Decomposition of Light--Light, Heat,
and Actinism--Blue Paper and Color for the Walls of the Operating Room--
Proportions of Light, Heat, and Actinism composing a Sunbeam--
Refraction--Reflection--Lenses--Copying Spherical Aberration--
Chromatic Aberration.

It is advisable that persons engaging in the Daguerreotype art should have
at least a little knowledge of the general principles of light and optics.
It is not the author's design here to give a full treatise on these subjects,
but he only briefly refers to the matter, giving a few facts.

It has been well observed by an able writer, that it is impossible to trace
the path of a sunbeam through our atmosphere without feeling a desire
to know its nature, by what power it traverses the immensity of space,
and the various modifications it undergoes at the surfaces and interior
of terrestrial substances.

Light is white and colorless, as long as it does not come
in contact with matter. When in apposition with any body,
it suffers variable degrees of decomposition, resulting in color,
as by reflection, dispersion, refraction, and unequal absorption.

To Sir I. Newton the world is indebted for proving the compound
nature of a ray of white light emitted from the sun.
The object of this work is not to engage in an extended theory
upon the subject of light, but to recur only to some points
of more particular interest to the photographic operator.

The decomposition of a beam of light can be noticed by exposing
it to a prism. If, in a dark room, a beam of light be admitted
through a small hole in a shutter, it will form a white round spot
upon the place where it falls. If a triangular prism of glass
be placed on the inside of the dark room, so that the beam
of light falls upon it, it no longer has the same direction,
nor does it form a round spot, but an oblong painted image of
seven colors--red, orange, yellow, green, blue, indigo, and violet.
This is called the solar spectrum, and will be readily understood
by reference to the accompanying diagram, Fig. 1.

[page 133]

To those who are unacquainted with the theory of light
(and for their benefit this chapter is given), it may be a matter
of wonder how a beam of light can be divided.

[amdg_1.gif]

This can be understood when I say, that white light is a bundle
of colored rays united together, and when so incorporated,
they are colorless; but in passing through the prism
the bond of union is severed, and the colored rays come
out singly and separately, because each ray has a certain
amount of refracting (bending) power, peculiar to itself.
These rays always hold the same relation to each other,
as may be seen by comparing every spectrum or rainbow;
there is never any confusion or misplacement.

There are various other means of decomposing

[page 134]

white light besides the prism, of which one of the principal
and most interesting to the Daguerreotypist is by reflection from
colored bodies. If a beam of white light falls upon a white surface,
it is reflected without change; but if it falls upon a red surface,
only the red ray is reflected: so also with yellow and other colors.
The ray which is reflected corresponds with the color of the object.
It is this reflected decomposed light which prevents the beautifully-colored
image we see upon the ground glass in our cameras.

[amdg_2.gif]

A sunbeam may be capable of three divisions--LIGHT, HEAT, and ACTINISM;
the last causes all the chemical changes, and is the acting
power upon surfaces prepared to receive the photographic image.
The accompanying illustration, Fig. 2, will readily bring
to the mind of the reader the relation of these one to another,
and their intensities in the different parts of a decomposed sunbeam.

The various points of the solar spectrum are represented in the order
in which they occur between A, and B, this exhibits the limits of the
Newtonian spectrum, corresponding with Fig. 1. Sir John Herschel and Seebeck
have shown that there exists, beyond the violet, a faint violet light,
or rather a lavender to b, to which gradually becomes colorless;
similarly, red light exists beyond the assigned limits of the red ray to a.
The greatest amount of actinic power is shown at E opposite the violet;
hence this color "exerts" the greatest amount of influence in the formation
of the photographic image.

(Blue paper and blue color have been somewhat extensively used by
our Daguerreotype operators in their operating rooms and skylights,
in order to facilitate the operation in the camera. I fancy, however,
that this plan cannot be productive of as much good as thought by some,
from the fact, that the light falling upon the subject, and then reflected
into the camera, is, coming through colorless glass, not affected
by such rays as may be reflected from the walls of the operating room;
and even if it were so, I conceive that it would be injurious,
by destroying the harmony of shadows which might otherwise occur.)
The greatest amount of white light is at C; the yellow contains less
of the chemical power than any other portion of the solar spectrum.
It has been found that the most intense heat is at the extreme red, b.

Artificial lights differ in their color; the white light
of burning charcoal, which is the principal light from candles,
oil and gas, contains three rays--red, yellow, and blue.
The dazzling light emitted from lime intensely heated,
known as the Drummond light, gives the colors of the prism
almost as bright as the solar spectrum.

If we expose a prepared Daguerreotype plate or sensitive paper
to the solar spectrum, it will be observed that the luminous power
(the yellow) occupies but a small space compared with the influence
of heat and chemical power. R. Hunt, in his Researches on Light,
has presented the following remarks upon the accompanying illustration:

"If the linear measure, or the diameter of a circle which shall
include the luminous rays,

[amdg_3.gif]

is 25, that of the calorific spectrum will be 42.10, and of the chemical
spectrum 55.10. Such a series of circles may well be used to represent
a beam from the sun, which may be regarded as an atom of Light,
surrounded with an invisible atmosphere of Heat, and another still
more extended, which possesses the remarkable property of producing
chemical and molecular change.

A ray of light, in passing obliquely through any medium of uniform density,
does not change its course; but if it should pass into a denser body,
it would turn from a straight line, pursue a less oblique direction,
and in a line nearer to a perpendicular to the surface of that body.
Water exerts a stronger refracting power than air; and if a ray of light
fall upon a body of this fluid its course is changed, as may be seen
by reference to Fig. 4.

[amdg_4.gif]

It is observed that it proceeds in a less oblique direction
(towards the dotted line), and, on passing on through, leaves the liquid,
proceeding in a line parallel to that at which it entered. It should be
observed that at the surface of bodies the refractive power is exerted,
and that the light proceeds in a straight line until leaving the body.
The refraction is more or less, and in all cases in proportion
as the rays fall more or less obliquely on the refracting surface.
It is this law of optics which has given rise to the lenses in our
camera tubes, by which means we are enabled to secure a well-delineated
representation of any object we choose to picture.

When a ray of light passes from one medium to another, and through that into
the first again, if the two refractions be equal, and in opposite directions,
no sensible effect will be produced.

The reader may readily comprehend the phenomena of refraction,
by means of light passing through lenses of different curves,
by reference to the following diagrams:--

[amdg_5.gif]

Fig 5 represents a double-convex lens, Fig. 6 a double-concave, and Fig.
7 a concavo-convex or meniscus. By these it is seen that a double-convex
lens tends to condense the rays of light to a focus, a double-concave
to scatter them, and a concavo-convex combines both powers.

If parallel rays of light fall upon a double-convex lens, D D, Fig.
8, they will be refracted (excepting such as pass directly through the centre)
to a point termed the principal focus.

[amdg_8a.gif]

The lines A B C represent parallel rays which pass through the lens,
D D, and meet at F; this point being the principal focus,
its distance from the lens is called the focal length.
Those rays of light which are traversing a parallel course,
when they enter the lens are brought to a focus nearer
the lens than others. Hence the difficulty the operator
sometimes experiences by not being able to "obtain a focus,"
when he wishes to secure a picture of some very distant objects;
he does not get his ground glass near enough to the lenses.
Again, the rays from an object near by may be termed diverging rays.
This will be better comprehended by reference to Fig.
9, where it will be seen that the dotted lines, representing

[amdg_9.gif]

parallel rays, meet nearer the lenses than those from the point A. The
closer the object is to the lenses, the greater will be the divergence.
This rule is applicable to copying. Did we wish to copy a 1/6
size Daguerreotype on a l/l6 size plate, we should place it in
such a position to the lenses at A that the focus would be at F,
where the image would be represented at about the proper size.
Now, if we should wish to copy the 1/6 size picture, and produce
another of exactly the same dimensions, we have only to bring it
nearer to the lenses, so that the lens D E shall be equi-distant from
the picture and the focus, i. e. from A to B. The reason of this is,
that the distance of the picture from the lens, in the last copy,
is less than the other, and the divergence has increased, throwing,
the focus further from the lens."

These remarks have been introduced here as being important
for those who may not understand the principles of enlarging
or reducing pictures in copying.

I would remark that the points F and A, in Fig.
9, are termed "conjugate foci."

If we hold a double-convex lens opposite any object, we find that an
inverted image of that object will be formed on a paper held behind it.
To illustrate this more clearly, I will refer to the following woodcut:

[amdg_10.gif]

"If A B C is an object placed before a convex lens, L L, every point
of it will send forth rays in all directions; but, for the sake
of simplicity, suppose only three points to give out rays,
one at the top, one at the middle, and one at the bottom;
the whole of the rays then that proceed from the point A, and fall
on the lens L L, will be refracted and form an image somewhere on
the line A G E, which is drawn direct through the centre of the lens;
consequently the focus E, produced by the convergence of the rays
proceding from A, must form an image of A, only in a different
relative position; the middle point of C being in a direct line
with the axis of the lens, will have its image formed on the axis F,
and the rays proceeding from the point B will form an image at D;
so that by imagining luminous objects to be made up of all infinite
number of radiating points and the rays from each individual point,
although falling on the whole surface of the lens, to converge again
and form a focus or representation of that point from which the rays
first emerged, it will be very easy to comprehend how images are formed,
and the cause of those images being reversed.

"It must also be evident, that in the two triangles A G B
and D G E, that E D, the length of the image, must be to A B,
the length of the object, as G D, the distance of the image,
is to G B, the distance of the object from the lens.

It will be observed that in the last cut the image produced
by the lens is curved. Now, it would be impossible to produce
a well-defined image from the centre to the edge upon a plain surface;
the outer edges would be misty, indistinct, or crayon-like. The
centre of the image might be represented clear and sharp on
the ground glass, yet this would be far from the case in regard
to the outer portions. This is called spherical aberration,
and to it is due the want of distinctness which is frequently
noticed around the edges of pictures taken in the camera.
To secure a camera with a flat, sharp, field, should be the object
of every operator; and, in a measure, this constitutes the great
difference in cameras manufactured in this country.

Spherical aberration is overcome by proper care in the formation of the lens:
"It can be shown upon mathematical data that a lens similar to that given
in the following diagram--one surface of which is a section of an ellipse,
and the other of a circle struck from the furthest of the two foci of
that ellipse--produces no aberration.

"At the earliest period of the employment of the camera obscura,
a double-convex lens was used to produce the image; but this form
was soon abandoned, on account of the spherical aberration so caused.
Lenses for the photographic camera are now always ground of
a concavo-convex form,

[amdg_11.gif]

or meniscus, which corresponds more nearly to the accompanying diagram."

Chromatic Aberration is another difficulty that opticians have to contend with
in the manufacturing of lenses. It will be remembered, that in a former page
(133) a beam of light is decomposed by passing through a glass prism giving
seven distinct colors--red, orange, yellow, green, blue, indigo and violet.

Now, as has been said before, the dissimilar rays having an unequal degree
of refrangibility, it will be impossible to obtain a focus by the light
passing through a double-convex lens without its being fringed with color.
Its effect will be readily understood by reference to the accompanying cut.

If L L be a double convex-lens, and R R R parallel rays of white light,
composed of the seven colored rays,

[amdg_8b.gif]

each having a different index of refraction, they cannot be refracted
to one and the same point; the red rays, being the least refrangible,
will be bent to r, and the violet rays, being the most refrangible, to v:
the distance v r constitutes the chromatic aberration, and the circle,
of which the diameter is a l, the place or point of mean refraction,
and is called the circle of least aberration. If the rays of the sun
are refracted by means of a lens, and the image received on a screen
placed between C and o, so as to cut the cone L a l L, a luminous circle
will be formed on the paper, only surrounded by a red border, because it
is produced by a section of the cone L a l L, of which the external
rays L a L l, are red; if the screen be moved to the other side of o,
the luminous circle will be bordered with violet, because it will be
a section of the cone M a M l, of which the exterior rays are violet.
To avoid the influence of spherical aberration, and to render the phenomena
of coloration more evident, let an opaque disc be placed over the central
portion of the lens, so as to allow the rays only to pass which are at
the edge of the glass; a violet image of the sun will then be seen at v,
red at r, and, finally, images of all the colors of the spectrum in
the intermediate space; consequently, the general image will not only
be confused, but clothed with prismatic colors."

To overcome the difficulty arising from the chromatic aberration,
the optician has only to employ a combination of lenses of opposite
focal length, and cut from glass possessing different refrangible powers,
so that the rays of light passing through the one are strongly refracted,
and in the other are bent asunder again, reproducing white light.

To the photographer one of the most important features, requiring his
particular attention. is, that he be provided with a good lens.
By the remarks given in the preceding pages, he will be enabled, in a measure,
to judge of some of the difficulties to which he is occasionally subjected.
We have in this country but two or three individuals who are giving their
attention to the manufacture of lenses, and their construction is such,
that they are quite free from the spherical or chromatic aberration.

CHAPTER V.

To make Plates for the Daguerreotype--Determining the Time of Exposure
in the Camera--Instantaneous Process for Producing Daguerreotype--
Galvanizing the Daguerreotype Plate--Silvering Solution--
Daguerreotype without Mercury--Management of Chemicals--
Hints and Cautions--Electrotyping--Crayon Daguerreotypes--
Illuminated Daguerreotypes--Natural Colors in Heliography--
Multiplying Daguerreotypes on one Plate--Deposit in Gilding--
Practical Hints on the Daguerreotype.

TO MAKE PLATES FOR THE DAGUERREOTYPE.

I do not give the method employed by our regular plate manufacturers;
this is not important, as the operator could not possibly profit
by it from the fact of the great expense of manufacturing.
The following will be found practical:

Procure a well planished copper plate of the required size,
and well polish it, first with pumice stone and water,
then with snake stone, jewelers' rouge. Plates can be
purchased in a high state of preparation from the engravers.
Having prepared the copper-plate, well rub it with salt and water,
and then with the silvering powder. No kind answers better
than that used by clock-makers to silver their dial-plates.
It is composed of one part of well washed chloride of silver,
five parts of cream of tartar, and four parts of table salt.
This powder must be kept in a dark vessel, and in a dry place.
For a plate six inches by five, as much of this composition
as can be taken up on a shilling is sufficient.
It is to be laid in the centre of the copper, and the figures
being wetted, to be quickly rubbed over every part
of the plate, adding occasionally a little damp salt.
The copper being covered with the silvering is to be speedily
well washed in water, in which a little soda is dissolved,
and as soon as the surface is of a fine silvery whiteness,
it is to be dried with a very clean warm cloth. In this state
the plates may be kept for use. The first process is to expose
the plate to the heat of a spirit flame, until the silvered
surface becomes of a well-defined golden-yellow color;
then, when the plate is cold, take a piece of cotton,
dipped in very dilute nitric acid, and rub lightly over it
until the white hue is restored, and dry it with very soft
clean cloths. A weak solution of the hydriodate of potash,
in which a small portion of iodine is dissolved, is now passed
over the plate with a wide camel's hair brush. The silver
is thus converted, over its surface, into an ioduret of silver;
and in this state it is exposed to light, which blackens it.
When dry, it is to be again polished, either with dilute acid
or a solution of carbonate of soda, and afterwards with dry cotton,
and the smallest possible portion of prepared chalk:
by this means a surface of the highest polish is produced.
The rationale of this process is, in the first place,
the heat applied dries off any adhering acid, and effects more
perfect union between the copper and silver, so as to enable
it to bear the subsequent processes. The first yellow surface
appears to be an oxide of silver with, possibly, a minute
quantity of copper in combination, which being removed leaves
a surface chemically pure.

Another Method.--The best and simplest mode with which we are
acquainted is to divide an earthenware vessel with a diaphragm:
one side should be filled with a very dilute solution of sulphuric acid,
and the other with either a solution of ferroprussiate of potash,
or muriate of soda, saturated with chloride of silver. The copper plate,
varnished on one side, is united, by means of a copper wire,
with a plate of zinc. The zinc plate being immersed in the acid,
and the copper in the salt, a weak electric current is generated,
which precipitates the silver in a very uniform manner over
the entire surface.

Another Method.--A piece of brass or of polished copper, brass is preferred,
is perfectly planished and its surface made perfectly clean.
A solution of nitrate of silver, so weak that the silver is
precipitated slowly, and a brownish color, on the brass, is laid
uniform]v over it, "at least three times," with a camel's hair pencil.
After each application of the nitrate, the plate should be rubbed gently
in one direction, with moistened bitartrate of potassa, applied with buff.
This coat of silver receives a fine polish from peroxide of iron and buff.
Proofs are said to have been taken on it, comparable with those obtained
on French plates.

M. SOLIEL'S PROCESS FOR DETERMINING THE TIME OF EXPOSURE IN THE CAMERA.

M. Soliel has proposed the use of the chloride of silver to determine the time
required to produce a good impression on the iodated plate in the camera.
His method is to fix at the bottom of a tube, blackened within, a piece
of card, on which chloride of silver, mixed with gum or dextrine, is spread.
The tube thus disposed is turned from the side of the object of which we wish
to take the image, and the time that the chloride of silver takes to become
of a greyish slate color will be the time required for the light of the camera
to produce a good effect on the iodated silver.

INSTANTANEOUS PROCESS FOR PROCURING DAGUERREOTYPES.

The following method of producing Daguerreotypes has by some been named
as above. Most experienced operators have been long acquainted with
the effect of the vapor of ammonia upon the chemically coated plate.
I will here insert Mr. W. H. Hewett's plan of proceeding.
This gentleman, in referring to it (published in 1845), says:

"This improvement consists in using the vapor of ammonia,
as an object to accelerate the action of light upon the plate.
The effect is produced upon a simple iodized plate, but still more upon
a plate prepared in the ordinary way, with both iodine and bromine.
By this means, the author obtained impressions instantaneously
in the sunshine, and in five to ten seconds in a moderate light;
and he hopes to be able to take moving objects. It can be applied
by exposing the prepared plate over a surface of water, to which a few
drops of ammonia have been added (sufficient to make it smell of ammonia);
or the vapor can be introduced into the camera during the action.
In fact, the presence of ammonia, in the operating-room, appears
to have a good effect, as it also neutralizes the vapors of iodine
and bromine that may be floating about, and which are so detrimental
to the influences of light upon the plate."

GALVANIZING THE DAGUERREOTYPE PLATE.

In consideration of the importance of galvanized plates, I shall endeavor
to give as plain and concise a manner of manipulation as possible.
For some time it was a question among the operators generally,
as to the beneficial result of electrotyping, the Daguerreotype plate,
but for a few years past our first operators have found it a fact,
that a well electro-silvered surface is the best for producing a portrait
by the Daguerreotype.

From my own experiments, I have found that a plate, by being galvanized,
can be rendered more sensitive to the operation of the light
in proportion of one to five, viz.: if a plate as furnished by
the market, be cleaned, polished, coated and exposed in the camera,
if the required time to freely develop an impression be ten seconds,
a similar plate prepared in like manner and galvanized,
will produce an equally well-defined image in eight seconds.
In connection with this subject, there is one fact worthy of notice;
a plate with a very heavy coating of pure silver, will not produce
an equally developed image, as a plate with a thinner coating, hence the
thin coating, providing it entirely covers the surface, is the best,
and is the one most to be desired. The experiment is plain and simple.
Let the slate receive a heavy or thick coating by the electrotype,
then polish, coat, expose in the usual manner, and the result will
be a flat, ashy, indistinct impression; when, on the other hand,
the thin coating will produce a bright, clear and distinct image,
with all the details delineated.

The style of battery best for the purpose has been, and now is,
a question of dispute among operators; some preferring the Daniell
battery to Smee's. Some claim the superiority of the first from its
uniformity of action; others, of the latter, for its strength.
I consider either good, and for the inexperienced would prefer the Daniell.
This is more simple in its construction, while it has certainty in action.
The more skillful electrotyper would prefer Smee's, and this is the one
most generally in use. I would remark that the plan of galvanizing plates
should be followed by every operator, and when once thoroughly tested,
no one will abandon it.

SILVERING SOLUTION.

To any desired quantity of chloride of silver in water add,
little by little, cyanide of potassium, shaking well at each addition,
until all the cyanide is dissolved. Continue this operation,
and add the cyanide, until all the precipitate is taken up
and held in solution.

This solution is now ready for the plate-cup. Enough water may be
added to cover any sized plate when held perpendicular in the cup.
The strength of the solution may be kept up by occasionally
adding the chloride of silver and cyanide of potassium.
There should alway be a very little excess of the cyanide.

The plate should be well cleaned and buffed, and the solution
well stirred before it is immersed. Care should be
observed to keep the solution clean, and allow no particle
of dust to come in contact with the surface of the plate.
The plate is now to be attached to the pole of the battery.

After remaining a short time, it assumes a blue color; take it out,
rinse freely with pure water, then dry with a spirit lamp,
and it is ready for buffing. Buff and coat in the usual manner.
Some operators are in the practice of immersing the plate
in the solution and buffing twice. This additional silvering
is no improvement wherever there has been a proper first coating.

Sometimes the operator is troubled with streaks or scum on the plate.
This may arise from three causes, all of which experience must teach
the experimenter to avoid; first, too great an excess of cyanide in
the solution; second, a lack of silver; third, the current too strong.
Another annoyance arises from the solution being dirty and the dirt
collecting on the surface. When this is the case, the dirt is sure
to come in contact with the surface of the plate as it is plunged into
the solution, and the result is a scum that it is difficult to dispose of.
This can be prevented only by frequent filtering. One thing should always
be borne in mind in electrotyping Daguerreotype plates--that in order to
secure a perfectly coated surface, the plate should be perfectly cleaned.
In this point, many who have tried the electrotype process have failed,
attributing their ill success to other than the proper cause.

DAGUERREOTYPES WITHOUT MERCURY.

The following process possesses some interest, and is
worthy a trial from operators. M. Natterer, of Vienna,
discovered a process for obtaining proofs on iodized plates
with the chloride of sulphur, without the use of mercury.
A plate of silver is iodized in the usual manner, and then placed
on the top of a vessel six or eight inches high, having at
the bottom, in a small cup, a few drops of chloride of sulphur;
it should remain exposed to the action of the vapor until
the sombre yellow color is changed to a red, after which it
is brought to a focus m the camera, where it is exposed
to the light in the camera, for about the time necessary
to produce an ordinary daguerreotype. The plate is then taken
out and examined in the camera by the light of a candle.
It often occurs that no trace of the image is as yet perceptible,
but if the plate is heated by placing over a spirit lamp
the unprepared side, or if left for some time in the dark,
or, lastly, if exposed only a few seconds to a weak, dimmed light,
the positive picture then appears with all its shades.
Of these three modes of bringing out the image, the second
is superior to the others.

MANAGEMENT OF CHEMICALS.

It is necessary, first of all, to know that you have a chemical
which is capable of producing good results when in skillful hands.
For this reason it is best to prepare your own quick, after some formula
which is known to be good. Those quick-stuffs which contain chloride
of iodine are noted for their depth of tone while they probably
operate with less uniformity than those which are destitute of it.
For operating under ordinary circumstances, especially with an
inferior light, probably no accelerator is more quick and sure than
Wolcott's. It also produces a very fine, white pleasing picture,
though lacking that depth of impression so much to be desired.
The dry quick operates with surety, and its use is simple and easy,
producing an impression much like Wolcott's. For those having a good
and permanent light, however, we would recommend a chemical giving
more body to the impression.

There is a class of accelerators called sensitives, claiming to
work in from three to ten seconds, which, however, will be found
very little, if any, more sensitive than this. We frequently
work it with the ordinary coating in twelve and fifteen seconds.
The manner in which the sensitives are worked is by coating very light.
In this way, a flat, shallow picture is obtained in a few seconds;
and the same can be done with any of the more volatile quicks.

It is a fact not generally known, that a plate coated in a light
chemical room is more sensitive than when coated in darkness.
By admitting a free, uniform light, and exposing the plate to it a few
seconds after coating, then timing short in the camera, a very light,
clear impression is obtained. The time in the camera is reduced
in proportion to the previous action of light. The shades, of course,
are destroyed, and the tone injured; still, for taking children,
we have succeeded better by this method than by the use of "sensitives."
The discovery of this principle was accidental, while operating where
the direct ray s of the sun, entering the window just before sunset,
fell on the curtain of our dark room, rendering it very light within.

The selection of iodine is not unimportant. Reject, at once,
that which has anything like a dull, black, greasy appearance;
and select that which is in beautiful large crystalline scales,
of a purple color, and brilliant steel lustre.

Solarization, and general blueness of all the light parts
of the picture, were formerly great obstacles to success,
though now scarcely thought of by first-class artists. Beginners in
the art, however, are still apt to meet with this difficulty.
It is occasioned by dampness in the iodine box, which causes
the plate to become coated with a hydro-iodide of silver,
instead of the iodide. The remedy is in drying your iodine.
If in summer, you can open your box and set it in sunshine
a few minutes; or if in winter, set it under a stove a short time.
The true method, however, is to dry it by means of the chloride
of calcium. It has such a remarkable affinity for water, that a
small fragment placed in the open air, even in the dryest weather,
soon becomes dissolved.

Take one or two ounces of this chemical, heat it in the drying bath,
or in a hot stove, to perfect dryness; place it in a small glass toy dish,
or large watch crystal, and set it in the centre of your iodine box.
Take this out and heat to dryness every morning. Adopt this process,
and with your mercury at a high temperature, you will never be troubled
with blue pictures.

Young operators are apt to impute all want of success in operating to
their chemicals, even though the cause is quite as likely to be elsewhere.
Failure is quite likely to occur from dampness in the buffs, or in the polish;
it is therefore necessary to be constantly on the guard in this quarter.
With a view to this, always scrape your buffs with a dull knife,
or with one blade of your shears, the first thing in the morning,
and after brushing them thoroughly, dry them, either in the sun, by a stove,
or in the buff-dryer. It is equally important that the polish and the brush
should be kept dry.

Want of success may arise from vapors of iodine or bromine in the camera box,
mercury bath, or even in the buffs. It is incredible how small
a quantity of these vapors will affect the effect of light when coming
in contact with the plate, after or during the exposure in the camera.
It is therefore necessary to be cautious not to mix chemicals,
nor open your boxes or bottles in your room, but take them out to do it.
Never hurry the operation through from lack of confidence in the result.
The fact of anything being out of order, forms no excuse for slighting
the process. If unsuccessful, do not pursue the same course every trial,
but vary with a view to detect the cause of the difficulty.

In case of a long series of failures, institute a regular course
of investigation, after this manner, commencing where the trouble
is most likely to occur:

1. Are the plates well cleaned?

2. Is the iodine dry? If the impressions come out blue,
you may rest assured it is not. Take out the iodine,
wipe and dry the box, and dry the calcium.

3. Is the quick battery of the right strength? If dry,
it must change the plate in from six to fifteen seconds.
If any of the chloride of iodine class, it may vary
from five seconds to a minute. Begin by coating light,
and increase on each trial, observing the effect.
If the light side of the picture seems loth to come out,
and shows no contrast with the dark side, it is to be inferred
that your battery is too strong, and must be reduced with water
or set out in the open air for a few minutes, with the lid off.
If working an old battery, never renew very strong,
or it will work dark and heavy. A battery, to work well,
should be gradually losing strength, but never gaining.
An old battery, however, may be quickened up and made to work
well for some time, by adding five of six drops of sulphuric acid,
repeating the quantity as often as necessary, providing always
that acid be not used in manufacturing the quick.

4. Have the plates lost their sensitiveness by being many times
exposed to mercury? Clean and burn them; but if French plates,
burn light, or you spoil them.

5. Are the buff s dry and clean? Examine the plate critically
after buffing to detect any appearance of scum or film on
the surface. If so, the longer you buff the more it shows.
Scrape and dry the buffs thoroughly.

6. Is the mercury free from scum and dirt? If not, filter.
Is it also far enough from the coating boxes? Should be at least
three feet, and kept covered.

7. Is the mercury sufficiently heated? This is important.
Long exposure, however, will answer the same purpose.

8. Are your lenses clean, and in proper place?

9. Are the tablets in focus with the ground-glass? If you can attribute
the failure to none of these, mix a new box of some other kind of quick,
say the dry, for instance. If you fail in the same manner here,
take time, wash your buffs, overhaul all the chemicals, and start anew.
Do not be discouraged.

There is no day so dark but that the sun will shine again.
We will close with this brief summary of advice:

Clean your plates. Keep everything dry. Keep the mercury hot.
Follow these instructions carefully, and you must succeed.

HINTS AND CAUTIONS.

First of all, cleanliness should be observed. When there is dust or dirt
about your room, particularly about the work-bench, failures will be frequent;
for the smallest particles of rotten-stone, when allowed to come in contact
with the buffs, will produce scratches on the surface of the plate,
which very much injures the operation, and often causes failures.

Dust flying about the room is injurious, if allowed to fall
on the plate, either before or after it has been coated,
as it causes black spots which cannot be removed.

The polished plate should not be allowed to come in contact with
a strong current of air, for it tends to oxidize the surface.
Breathing on the surface should also be avoided, for the same reason.

The plate should, in all cases, be buffed immediately
before using, and not allowed to stand any length of time.
It should be held with the polished face downward.

It is always best that the plate should be of the same temperature
of the atmosphere in the room.

Keep the camera and mercury-bath perfectly free from the vapors
of iodine and bromine; for the presence of the slightest degree
of either of the above will injure the impression in no small degree.
As a preventive, let the camera be exposed to the sun or fire
for a few minutes in the morning.

Filter your mercury often, to keep the surface free from film and dust.

The hyposulphite solution should be filtered through sponge every
time it is used.

The direct rays of light must not enter the camera in conjunction
with those reflected from the object; or the picture will be veiled,
and the color of the plate changed to a thick green.

If the plate be iodized only to a light-yellow, the result might
be of a bluish or grey tinge: and this is generally the case,
when the quick is new and strong, and there is an excess of it on
the plate, and yet not enough to form the bromide iodide of silver;
in which case it would wholly spoil the impression.

Your iodine will be found to operate more successfully, when the time
required for coating the plate does not fall short of fifteen seconds,
or exceed one minute.

Too quick coating can be avoided by using less iodine in your box.
In the summer months, when the weather is 80 deg. and over,
one quarter of an ounce, or even less, will work to advantage.

ELECTROTYPING.

I am indebted to Mr. J. H. Fitzgibbons for the following process,
which he employed in producing the excellent specimens he exhibited
at the Crystal Palace:

"I shall endeavor to lay down in as comprehensive a manner as possible the
method by which I have been enabled to produce the most satisfactory results.
I use a Smee's battery (another kind will do). After filling the cell,
of common size, nearly full with water; add about quarter of an ounce
of sulphuric acid. Mix this well, and let it stand for about three hours,
or until the action of the battery becomes weak, when it is in order to work
with a very uniform action. Put one pound of sulphate of copper in one quart
of water; stir it until the sulphate of copper is all dissolved, and then add
one half ounce of sulphuric acid and a quarter of an ounce of nitric acid.
This solution, well mixed, should be filtered, and it is ready for use.
It is very important that the solution should be kept clean, clear, and free
from all foreign substance. The above quantity of this solution will be
found sufficient for electrotyping a dozen of the sixth-size plates.
When it is required to be strengthened, it is only necessary to add a little
of the sulphate of copper.

"With the battery prepared as above, and the solution of sulphate
of copper in a vessel of proper dimensions to receive your plate,
connect the galvanic current, and immerse the impressioned plate,
letting it remain until a thin film of copper has been formed,
then the battery can be strengthened, and the impression will be
of sufficient thickness to be removed in from eight to twelve hours.
An old Daguerreotype plate attached to the opposite pole of the battery
(copper side towards the face of the plate to be electrotyped),
will answer the same purpose as the silver-plate.

"The great difficulty in taking an electrotype impression, and preserving
the original, has been attributed to the battery being too powerful.
I am led to believe from practice that the principal difficulty has been
in the Daguerreotype plate itself, for if we use an impression that has
been taken but a few days, and taken in the usual way, we will find
it difficult to succeed without spoiling both the copy and original,
and so also with an old impression.

"I have found the most certain method to be as follows:--
Coat the Daguerreotype plate as usual, except use less of
the accelerators, the proportion of iodine coating being greater,
of course the time of exposure in the camera will be lengthened.
Mercurialize it at about a temperature requiring to develop the image,
from six to eight minutes, at least. Gilding the Daguerreotype
has much to do towards producing a good electrotype copy.
This should be done by applying a little heat, and gilding very slowly,
giving a coating of gold with the greatest possible uniformity.
By this method, I have been enabled to produce any number of proofs.
I have produced a dozen from one impression, and it remains
as perfect as when first taken.

"By a little judgment and care the operator will be enabled to produce
the electrotype copy of the Daguerreotype plate without any difficulty.
The electrotype copy should be immediately put under a glass and sealed
in the same manner as the ordinary Daguerreotype."

CRAYON DAGUERREOTYPES.

This process is patented in the United States, by J. A. Whipple, of Boston,
and of course no honorable person will use it for his own benefit without
purchasing a right.

A white back-ground is generally employed, the object being to blur
the lower portion of the plate, leaving the head of the subject in relief.
Every Daguerreotypist is familiar with the fact that a motion
of any body between the camera and the sitter will cause a "blur."
Cut a piece of thin paper and scallop it, making a semicircle.
This is kept straight by means of a wire frame, and it is to be moved
in front of the lower part of the body of the sitter during the time
of exposure of the plate in the camera. Develop over mercury as usual,
and the result will be a crayon Daguerreotype.

Another method is to have a wheel with a hole cut through
it of a diameter of about 12 inches. This hole is so cut
as to leave teeth resembling those of a large saw.
This wheel is so arranged that it can be turned around,
which should be done during the time of exposure in the camera.
It must be placed between the camera and the sitter, and at such
a distance from the camera as to allow such proportion of the body
of the sitter be seen upon the ground-glass as is desired.
It will be readily seen that by turning this wheel during
the operation will produce the same result as the paper being
moved in the other method. The teeth make the "blur."
The side of the wheel towards the camera may be black, by which
means the result will be a dark instead of a light border.

ILLUMINATED DAGUERREOTYPES.

This process is also patented, and the remarks on the preceding subject
will apply in this case. The plate is prepared and exposed as in the
usual method of the Daguerreotype. A white back-ground is employed.
Let the head of the sitter come in the middle of the plate, and before
exposing it to the vapors of mercury, put a small mat or diaphragm,
having a small hole through it, over or directly on the surface of the plate.
This diaphragm should be bevelled, and the bevel should be towards the surface
of the plate; this, in order to prevent too sharp a line on the impression.
It will be readily seen that if an impressioned plate so covered is placed
over the mercury, it will be developed on such portions only as are exposed.
The principle is so familiar that further explanations are unnecessary.

NATURAL COLORS IN HELIOGRAPHY.

This subject is worthy the attention of every operator. The following
process is so plain and easy of trial that any Daguerreotypist can try it.
This is as given by Mr. James Campbell, and was published in Humphrey's
Journal of the Daguerreotype and Photographic Arts, vol. 5, page 11.
Mr. Campbell has done much to further the process announced by M. Neipce,
and his experiments have proved highly successful.

The following is submitted as worthy of trial:

"The proper preparation of the chloridated plate, to enable it to receive
colored impressions is an object of the first importance to those wishing
to experiment on it, and consequently requires particular notice.
The plate may be prepared by making it the positive pole of a battery,
and letting it at the same time be immersed in chlorine water.
The negative pole should be a slip of platinum. All the colors may
be produced from a plate so prepared if the chlorine and water are in
the right proportions; but generally one color or the other predominates,
according to the amount of chlorine in the liquid. By adding the chlorides
of strontian, uranium, potassium, sodium, iron, or copper to the liquid,
various effects may be produced, and these bodies will be found to produce
the same color on the plate that their flame gives to alcohol.

"The honor of this discovery is due to M. Neipce.
Copper gives a variegated flame; hence many colors may be
impressed on a plate prepared with a solution of its chloride.

"M. Neipce recommends a solution of the mixed chlorides of copper
and iron, and it is with these, that I have been most successful.
As the chlorides of copper and iron are not much used in the arts,
they are not generally found for sale in the shops; and it may be
well to furnish those not much versed in chemistry with an easy
method of preparing them.

"They may be made directly from either metal by dissolving it
in hydrochloric acid; but they may be formed by a cheaper method,
and by which also the acid fumes are avoided.

"Sulphate of iron or copper, or both together, may be dissolved
in water and then neutralized with common crude potash, or its
carbonate or bicarbonate--known commonly as pearlash and saleratus.
If either of the latter be used, there will be formed sulphate
of potash and a carbonate of the metal used, and there will also
be a considerable effervescence of carbonic acid, which will,
if care is not taken, cause the mixture to run over the vessel.
After the copper or iron salt is neutralized, which is known
by its ceasing to effervesce, the carbonate of the metal
will settle slowly, and will at first nearly fill the vessel.
The supernatant fluid, which is sulphate of potash in solution,
may now be carefully poured off, and its place filled with water;
this operation should be repeated several times until the water which
passes off is tasteless. The carbonate of the metal rapidly changes
to an oxide by contact with the air, and it will generally be found,
when it is sufficiently washed, that it is at least half oxide.
On adding hydrochloric acid cautiously to the mixture, a chloric
of the metal will be formed, and carbonic acid will be evolved
from the remaining carbonate. The chloride formed is soluble;
but as there are two chlorides of these metals, and we wish
to produce the one which contains the most chlorine, it is best
to add the acid cautiously until the solution is decidedly acid.
After filtering the solution, it is fit for use; and it should be
preserved in well-stoppered bottles. The water used should be rain
or distilled water.

"About one part of the mixed chlorides should be used to three
or four of water.

"The battery may be either Smee's, Daniell's, or Grove's;
if of either of the former, it should be of two series;
if of the latter, one cup is sufficient.

"The plate on being immersed in the liquid, almost instantly takes
a violet color. It should be allowed to remain from two to five minutes,
according to the strength of the battery, and until it becomes nearly black.
It should now be carefully washed, and afterwards heated over a spirit
lamp until it takes a cherry-red color, and it is then ready for exposure
in the camera. Before speaking of exposing the plate, it may be well
to speak of some difficulties which the inexperienced operator may find
in preparing it. If the battery is not in good order, and a sufficient
current is not passed through the solution, the plate will become coated--
and apparently almost as well as when the battery is working well--
but on exposure it will give a negative picture, and but little colored;
while if the battery is in good order, the impression is invariably positive.

"Sometimes on heating the plate after washing, the surface
is covered with spots or assumes a variegated appearance.
This indicates that the solution is impure, or that the plate
have not been thoroughly washed and are still contaminated
with the soluble chlorides which are contained in the solution.

"From the fact that the plate if prepared with positive electricity gives
a positive picture, while it prepared otherwise it gives a negative,
it is evident that electricity plays an important part in this process.
The same is true to some extent with the compounds formed
with iodine, bromine. and fluorine.

"On heating the plate, the brown coating of chloride melts into a translucent
enamel, and the heat should be withdrawn when a cherry-red color is produced.
It the heat is continued longer, the plate assumes a lighter color,
and becomes less sensitive; and the enamel will finally scale off.
To produce a picture by the ordinary process of M. Neipce, unaccelerated, it
should be exposed for from three to five hours to sunlight in the camera,
though pictures may be procured by contact, in from fifteen to thirty minutes."

MULTIPLYING DAGUERREOTYPES ON ONE PLATE.

I have produced some interesting specimens of the Daguerreotypic art,
by exposing in the camera only a portion of the sensitive plate to
the action of light. When on the exposed portion an image is formed,
then taking the tablet into the dark room, change ends and expose
the sensitive portion, and produce another image, developing as usual.
This plan is adapted for taking likenesses for lockets.
Two images can be presented as sitting side by side, by covering
half the plate with black paper, and exposing as before.
In this manner we have been enabled to surprise persons by exhibiting
their portrait on the same plate with a stranger's. Daguerreotypists
must be cautious in practicing this, as it might not be agreeable
to the parties whose likenesses are together, by the above process.
It is impossible to produce an impression without a line being seen
where the edge of the paper prevented the operation of the light.

I have recently seen a fine specimen produced by another plan,
which far exceeds the above, there being no line, or any
peculiarity denoting two exposures. The specimen referred to,
was a gentleman represented on one plate by two full length portraits.
This was produced by using a black velvet for the background.
The plate was exposed sufficient time to produce one impression,
and then the gentleman assumed another position, and is repeated
as looking at himself. From the fact that the time required to develop
black velvet being so much longer than that for producing a portrait,
we are enabled to produce the above interesting results.

DEPOSIT IN GILDING.

Regarding specks from bad water, I would remark that gilding
should be made only with distilled water. Thus made,
it produces very little deposit, even by long keeping.
It therefore preserves its original strength, and works
with great uniformity.

Every grain of deposit contains at least 7-10 its
weight of gold, easily discoverable by the blowpipe.
Such gilding is continually deteriorating, which with
good chloride and distilled water may be prevented.
Distilled water should also be used for the hyposulphite.
and for cleaning plates. Any good, clear water may be
afterwards used for washing off, with equally good results.
I am very rarely troubled with specs, and deem this as
the main reason.

With a portable still attached to a cooking stove, I obtain
half a gallon of water per hour, and with very little trouble.
A small tin retort or still connected with a Leibig's condenser,
would not add much to the "traps" of the travelling operator,
and save him many a disreputable specimen.--T. J. BAILEY.--
Humphrey's Journal.

PRACTICAL HINTS ON THE DAGUERREOTYPE.

The following is from Humphrey's Journal, vol. 5, and from the pen
of Dr. WM. HARRINGTON, one of the most able writers upon the subject
of the Daguerreotype in this country:

THE CAUSE OF THE DIFFICULTY THAT SOMETIMES OCCURS TO PREVENT THE
PRODUCTION OF A CLEAR IMPRESSION UPON A DAGUERREOTYPE PLATE.

Beyond all doubt this is traceable to dampness.
Truly this is not a new thought; but where does this dampness
come from? How does it originate, and where is it located?
Generally it has been referred to a point entirely remote
from its real location.

This dampness exists particularly upon the surface of the plate;
is obviously derived immediately from the atmosphere;
and is owing to a certain relative temperature of the plate
with the hygrometric condition of the atmosphere.

Whenever this relation exists between the plate and atmosphere,
a precipitation of moisture takes place upon the surface of
the plate, which render all efforts at polishing impracticable.
This interference is not confined to the buffing operation alone,
but sometimes is discoverable even in the ordinary process of scouring.
Every one at all experienced in this art will remember that it
is not always an easy matter for him, by scouring, to bring his
plate to the desired lustre. All his efforts become unavailing;
the more he rubs, the duller the surface of his plate appears;
and although he renews his cotton repeatedly, still he is obliged
to content himself with an unsatisfactory finish.

This relative condition is not confined to any particular season
of the year, nor to any certain thermometric temperature;
but may occur in summer as well as in winter; the weather being
warm or cold, wet or dry, clear or cloudy, raining or shining.
Under any of these circumstances, if the relation of the plate
and atmosphere be such as to invite upon the plate a precipitation
of humidity from the atmosphere, the prospect of producing a clear
impression is quite problematical.

It is reasonable to expect this occurrence from the fact that metal is a
good radiator, and radiation reduces the temperature of a metallic body below
that of the atmosphere. Consequently, if this relative condition happens,
the result will be as I have stated.

Bodies may be colder than the atmosphere and yet derive no moisture from it;
while at the same time the driest atmosphere is not devoid of moisture,
but will part with it under certain conditions.

Assuming for granted that this relative condition between
the plate and atmosphere, disposing the former to receive
the humidity of the latter, constitutes the great obstacle
the operator has to contend with in producing, a clear
proof upon the plate, the remedy naturally suggests itself,
and is very simple. It consists in merely heating the plate
above the temperature of the atmosphere, previous to polishing,
and retaining that temperature during the operation.
Various measures might be devised to effect the desired object;
one of which consists of a sheet-iron box, heated from the inside
by a spirit-lamp, upon the top of which are to be kept
the plates ready to undergo the process of being polished;
the blocks of the swing or any other vice; or the iron bed
belonging to Lewis's vice.

In cold weather, when it is necessary to keep a fire in the preparation room,
all of the above may be so arranged in the vicinity of the fire as to receive
the requisite degree of heat for the purpose specified.

This part of the subject, however, is left entirely for the ingenuity
of the operator. No matter by hat means he accomplishes the object;
all that is required is to heat the plate above the temperature of
the atmosphere and retain that heat during the process of polishing.

Since the adoption of this method. in connection with my partner,
T. J. Dobyns, even in this humid climate of ours, when everything
in the room is dripping with moisture, it has been attended
with invariable success.

CHOICE OF PLATES, ETC.

In the great catalogue of complaints made by operators,
none is more common than that alleged against the quality
of plates in general use. Although the greatest diversity
of opinion exists upon this subject, nevertheless the plates
of every manufactory share in this universal condemnation.

To be sure it cannot be denied but that this necessary article
of utility in the photographic art has undergone a sad deterioration
in quality owing to the increasing demand and great reduction in price--
the plates of the present day being by no means so heavily coated
with silver as formerly--but the complaint alluded to is not predicated
so much upon the thinness of silver as upon a mysterious something
which has conferred upon the plates the epithet of not good.

That this complaint is in a great measure groundless appears evident
from the fact that while, with the same brand of plates one operator can
work successfully, another encounters the greatest difficulty; while one
is able to produce beautifully clear and altogether satisfactory results,
the other labors under the troublesome annoyance of innumerable specks,
large dark insensitive patches and brown map-like portions, together with
divers other blemishes, sufficient to prevent him from obtaining anything
like a tolerable impression.

From this wide difference in the results of the two operators using
identically the same article, it is but reasonable to conclude
that the complaint is founded in error; while the inference
is no more than just, that the fault may be traced to a want
of practical skill on the part of the complaining operator himself;
rather than to the inferior quality of the plates.

The question, then, whether the plates are unfit for use,
or whether those who pronounce them so understand
how to use them, appears to be satisfactorily answered.
It therefore becomes a matter worthy of investigation,
to ascertain what superior judgment and skill one operator
possesses over another which enable him to work successfully
a quality of plate, pronounced by the other entirely useless.

Suppose we make a critical examination of one of the repudiated plates.
From its external appearance we have little hesitation in pronouncing it
to be French; indeed, this presumption is strongly corroborated by the fact
that it is ornamented upon one of its corners with a brand to designate
the manufactory from which it emanated.

Upon close inspection we cannot fail to notice a striking peculiarity
upon the surface; the roughness is very remarkable; the planishing
hammer has left amazingly visible indications of its busy work.
One would suppose the manufacturer intended the surface of the plate
to represent the undulations of the sea, instead of that smooth
and level character so strongly recommended by M. Daguerre.

Such a plate necessarily requires at the hand of the operator
considerable labor before the surface is in a proper
condition to receive a suitable polish from the buffer.
The least reflection in the world should teach any one that so long
as the undulatory character continues upon the surface of the plate,
it is in a very imperfect condition for buffing, because the buffer
cannot touch every point equally; the elevated portions alone
receiving a high degree of polish while the depressed portion,
from their roughness acting as nuclei, gather dust, rouge,
and other foreign bodies, so detrimental to sensitiveness.
The secret of the superior judgment and skill of one operator
over another, is intimately connected with this point:
his success depends very much upon the first process of
cleaning the plate.

Let us examine the manipulation of the complaining operator.
He takes one of these plates and gives it a careful scouring with
rotten-stone and alcohol or any other liquid preferred for this part
of the operation--that is, he gives it what he terms a careful scouring--
very gently indeed because, from the frequent trials he is in
the habit of making in the camera, he fears he will rub the silver
entirely away before he succeeds in obtaining a good impression.
The dark patches, specks, and granular appearance resulting entirely
from the unevenness of the surface of the plate, look like copper to him,
and he is surprised that he should have rubbed away the silver so soon,
particularly by such delicate handling.

The judgment and experience of the successful operator, however,
teach him that scouring injures a plate less than buffing.
He knows that unless the hammer marks be obliterated,
he cannot by the buffer produce a surface of uniform polish
and sensitiveness, without which a fair proof is extremely doubtful;
he knows that the time employed in the preliminary operation
of cleaning the plate properly is economy.

There is a style of French plates in the market, denominated heavy,
which are truly excellent, if properly managed. Much patience, however,
is required to remove the marks of the hammer; but with tripoli and alcohol
the surface is readily cut down, and the plate is then susceptible of a
beautiful black lustre by polishing with the buffer. The complaining
operator could not succeed by his own method with one of the plates;
he would encounter all manner of clouds and other unaccountable phenomena;
he would imagine this plate entirely worn out before it was half cleaned,
and soon fix in his own estimation the reputation of the heavy plate.

In making a choice of plates, therefore, it would appear to be a matter
of perfect indifference with an experienced operator what kind he would use,
except so far only as the labor required in cleaning them was to be
taken into consideration.

The distinction between a scale plate, a Scovill No. 1,
S. F., heavy A, star, crescent, eagle, or any other brand,
consists in the superior finish of some, and the thinness
of the silver in the cheaper qualities.

Consequently, let the complaining operator but employ the diligence
inculcated in this article, to clean his plate thoroughly,
so as to bring it to a perfectly even and level surface,
and he will seldom be troubled with specks, clouds, dark patches,
and the host of other obstacles which heretofore have tormented him.

CHAPTER VI.

AN ACCOUNT OF WOLCOTT AND JOHNSON'S EARLY EXPERIMENTS, IN THE DAGUERREOTYPE.
BY JOHN JOHNSON.

[From Humphrey's Journal, vol. ii 185l]

As a general thing, however perfect any invention may be deemed
by the inventor or discoverer, it falls to the lot of most,
to be the subject of improvement and advancement, and especially
is this the case with those new projects in science which open
an untrodden field to the view of the artisan. Such has been,
in an eminent degree, the case with the discovery first announced
to the world by Mons. Jean Jaques Claude Daguerre, of Paris,
in the year 1839, and which excited unbounded astonishment,
curiosity and surprise. It may be questioned had any other
than Daguerre himself discovered a like beautiful combination,
whether the world would have been favored with details exhibiting
so much care, patience and perseverance as the Daguerreotype
on its introduction. Shortly after, these details reached
the United States, by Professor S. F. B. Morse, of New York,
who was, at the time of the discovery, residing in Paris.
By this announcement, the whole scientific corps was set in operation,
many repeating the experiments, following carefully the directions
pointed out by Daguerre, as being necessary to success.
Among the number in the United States, was Alexander S. Wolcott
(since deceased) and myself; both of this city. On the morning
of the 6th day of October, 1839, I took to A. Wolcott's residence,
a full description of Daguerre's discovery, he being at
the time engaged in the department of Mechanical Dentistry,
on some work requiring his immediate attention, the work being
promised at 2 P.M. that day; having, therefore, no opportunity
to read the description for himself (a thing he was accustomed
to do at all times, when investigating any subject). I read to him
the paper, and proposed to him that if he would plan a camera
(a matter he was fully acquainted with, both theoretically and
practically), I would obtain the materials as specified by Daguerre.
This being agreed to, I departed for the purpose, and on my
return to his shop, he handed me the sketch of a camera box,
without at all explaining in what manner the lens was to be mounted.
This I also undertook to procure. After 2, P.M., he had
more leisure, when he proceeded to complete the camera,
introducing for that purpose a reflector in the back of the box,
and also to affix a plate holder on the inside, with a slide to obtain
the focus on the plate, prepared after the manner of Daguerre.
While Mr. Wolcott was engaged with the camera, I busied myself
in polishing the silver plate, or rather silver plated copper;
but ere reaching the end preparatory to iodizing, I found I had
nearly or quite removed the silver surface from off the plate,
and that being the best piece of sliver-plated copper
to be found, the first remedy at hand that suggested itself,
was a burnisher, and a few strips were quickly burnished
and polished. Meantime. the camera being finished, Mr. Wolcott,
after reading for himself Daguerre's method of iodizing,
prepared two plates, and placing them in the camera,
guessed at the required time they should remain exposed
to the action of the light; after mercurializing each in turn,
and removing the iodized surface with a solution of common salt
two successful impressions were obtained, each unlike the other!
Considerable surprise was excited by this result, for each plate
was managed precisely like the other. On referring to Daguerre,
no explanation was found for this strange result; time, however,
revealed to us that one picture was positive, and the other negative.
On this subject I shall have much to say during the progress
of the work. Investigating, the cause of this difference occupied
the remainder of that day. However, another attempt was agreed upon,
and the instruments, plates, etc., prepared and taken up
into an attic room, in a position most favorable for light.

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