Towler, John. The Silver Sunbeam. Joseph H. Ladd, New York: 1864. Electronic edition prepared from facsimile edition of Morgan and Morgan, Inc., Hastings-on-Hudson, New York. Second printing, Feb. 1974. ISBN 871000-005-9

Chapter XXXVI.

MY instructions hitherto have been limited strictly to the chemical and mechanical manipulations that occur in that department of photography denominated the Wet Collodion Process. This process will ever remain the predominant mode of conducting photographic operations in the room; it is preferred, too, by many tourists in the field. The inconvenience, however, of dragging along over mountain and valley, or of stowing away on steamer or on the cars, a complete miniature operating gallery, has suggested the idea of superseding all this trouble by the discovery of a dry process. Several processes have been discovered which are more or less successful, and all very practical; but it must be confessed that the same degree of sensitiveness in the dry process has not yet been attained as in the wet process--instantaneous pictures are the result only of the latter. It appears natural for us to expect such a result; chemical combinations and reductions are effected most easily when the mole-cubes of matter are in such a condition as to have freedom of locomotion, by which new molecular arrangements can be formed, in accordance with the new electro-chemical attractions and repulsions superinduced by the contact of dissimilar bodies.

For landscape and especially for architectural photography, for copying, as well as for every case of photography in still life, where the time of exposure is not important, dry plates are decidedly superior to wet ones because of the uniformity of their condition during the time of their exposure; wet plates, on the contrary, by desiccation are continually changing; and one of these changes--the concentration of the nitrate of silver during evaporation--is supposed to be one of the causes that produce minute apertures in the film, and is certainly the cause of an irregularity in the reduction-process during development. The aim of a dry plate is to attain to a maximum of preservation of the sensitiveness for an indefinite time. It has happened hitherto that the ratio of this preservation is inversely as the time of exposure, or, probably in plainer terms, that the better the plate is l)re served so as to retain sensitiveness, the longer the time required to be exposed to the actinic influence to produce a given effect. The theory, that is, the rational elucidation of the action of reduction in a dry plate is still a problem; if the wet plate, after sensitization, he thoroughly washed and then exposed, no picture is developed by the reducing agent; but in the dry plate the film is very carefully washed and then coated with some preservative agent, as it is called, such as albumen, tannic acid, gelatine, honey, syrup, infusion of malt, glucose, etc., and then when otherwise properly prepared and dry, it will yield, when exposed and afterward subjected to the action of a reducing agent, an intense picture.

I say the rationale of this phenomenon is still a problem. Some suppose that the albuminous, collodio-albuminous, gelatinous, etc., film becomes permeable to the developer in the dry process; whilst the collodion film in its simple unpreserved condition is not so. Such a supposition is, however, the mere admission of our inability to render any satisfactory explanation; it is the admission of little more than the fact itself.

As yet, also, it is difficult to say which of the dry processes in vogue is absolutely the best; although perhaps the majority would throw the weight of their opinion into the scale of the Tannin Process of Major Russell. The dry processes most conspicuously on the carpet are: the Albumen Process; the Collodio-Albumen or Taupenot Process; the Gelatine or Dr. Hill Norris's Process; the Tannin Process of Major Russell; and the Resin Process.

The Albumen Process.

This process was in use several years before that of collodion; Niepce de St. Victor first produced negatives with it. It is still employed by some of the most distinguished artists in Europe in the production of stereographs, both negative and positive, also of photographs of interiors, and in general of pictures of still life. Its theory is very simple; but its manipulation demands great care and skill.

Formula for Iodized Albumen.

The white of egg 10 ounces.
Iodide of ammonium 44 grains.
Distilled water, (sufficient to dissolve the iodide.)

Dissolve the iodide in the water, then add the solution by degrees to the white of egg, entirely freed from the germ and yolk, and beat the egg up well with a wooden spatula until it is completely converted into froth. This operation must be performed in a place as perfectly free from dust as possible; and then the albuminous mixture is covered with a clean sheet of paper and put aside to settle for a number of hours. After standing the required time, the surface becomes covered with a sort of incrustation, through which an aperture is made to allow the iodized albumen to flow out. In some formulas for iodizing the albumen, a bromide is used and a small quantity of free iodine.

Formula No. 2.

The white of egg 10 ounces.
Iodide of potassium 44 grains.
Bromide of potassium, 15 grains.
Free iodine 2 grains.
Distilled water, (sufficient to dissolve the salts.)

Beat up the white of egg as before. The operation is best performed when the temperature of the room is low. A few hours previous to the operation of coating the plates, mop The floor and wipe all the shelves with a clamp cloth--the great difficulty in this process is the deposition of dust or fibers on the glasses during the time they are drying.. Another trouble (and these are about all the difficulties the operator has to contend against) is the flowing of the plate with an even and uniform film, and its uniform retention on the plate until dry. The plates, of course, must be perfectly clean in this process, as in every other for negative purposes-

Several methods have been proposed by which the plate can be covered with albumen, most of which, no doubt, have deterred photographers from undertaking this branch. I believe the best method is to flow the plate exactly as you would cover it with collodion; amid if the albumen ceases to flow in certain parts, to use a glass triangle and thus scrape it as it were over those parts. It is necessary in all cases to pour upon the plate much more albumen than you would collodion, in order to cover the plates easily and effectually; most of the superfluous quantity is poured off at the right nearest corner; whilst the residual surplus is made to traverse the plate diagonally to the farthest left corner and then flow off into the receiving vessel. If any surplus still remains it is flowed gently toward the middle of the plate and equalized as much as possible over the whole surface. The next operation is the

Drying Process.

This operation, in general, has been rendered very tedious and inefficient; the plates were allowed to dry spontaneously, which occupied several hours, and in the mean while the albumen film became contaminated with the deposition of dust, which completely spoiled the plates. By the following method they may be dried in a few minutes. Prepare a metallic table, that is, a plate of iron or other metal supported on three legs, sufficiently capacious for the purpose. Beneath this an alcohol lamp is kept burning, by which the plate is maintained at any given temperature by the adjustment of the wick, or its distance from the plate. Next, supposing that stereoscopic negatives are the objects of manipulation, prepare a piece of brass or iron longer and wider than the stereoscopic plate by a quarter of an inch; cut out from this a piece of the same shape as the negative plate, but shorter in its two dimensions by a quarter of an inch. On one end rivet a metallic handle, which may be fixed into a wooden one. Turn up a ledge on either side, as also on either end, (as far as practicable on the nearer end by reason of the handle,) about one tenth of an inch high. It is evident that so constructed, the negative can lie on this skeleton plate and within the ledges. Place the plate, albumenized as above, on this metallic plate, and, taking hold of the handle with the right hand, bring it into a horizontal position over the heated plate at a proper distance above it; equalize the albumen by inclining the hand as required and, keeping the hand in continual motion, the film will soon dry uniformly, and the plate can then be put away for future use. So prepared it will keep for an indefinite time.

Sensitizing the Film.

An oblong flat porcelain or glass dish is preferred to the vertical bath for the purpose of sensitizing the film; and if the dish be made twice as long as required, it will answer the purpose best.

Formula for the Sensitizing Solution.

Nitrate of silver 1 ounce.
Acetic acid 5 ounces.
Distilled water 10 ounces.
Iodide of potassium 2 grains.

Lay the albumen plate along one side of the glass dish; then raising this side, pour into the inclined side a sufficient quantity of the bath; with a dexterous move raise the inclined side so that the fluid may flow over the albumen film in one quick continuous layer. By this contrivance all lines or marks of stoppage are avoided. This is a very necessary provision here; for the slightest hesitation or stoppage will infallibly show its effect on the negative. About half a minute will be sufficient to coagulate the albumen, and to sensitize the film. This operation is performed in the dark-room; whereas that of albumenizing takes place in diffused light. After sensitization--which occupies from thirty to fifty seconds--the plate is removed from the bath by raising it first with a bent silver hook, and then seizing it by one corner with the hand. It is then washed under the tap and left to soak in a dish of distilled water until the next plate is prepared. Finally, when it is supposed the free nitrate of silver has been thoroughly removed, it is used immediately or dried for future use. The quantity of acetic acid in the above formula may be diminished in many instances; its object is to prevent fogging, but it diminishes sensitiveness at the same time. If with half the quantity no fogginess supervenes, this quantity will be quite enough; by thus beginning with a small amount of acetic acid, and gradually increasing until fogging ceases, more rapid effects may be obtained in the exposure. When the plates are kept long they undergo a species of decomposition which induces fogginess; the fresh plates, therefore, are in the best condition for producing normal results with the greatest rapidity, because the sensitizing bath requires the least amount of acid.

Blisters are apt to arise in the film by immersion in the sensitizing bath, or during the subsequent operations. These are frequently owing to the imperfect cleaning of the plates or in the clumsy flowing of the albumen. Gummy substances are sometimes added to the albumen in order to render it more adherent or less contractile.

Exposure in the camera.

The amount of exposure will depend on the conditions of the light, the focal length of the lens, and the sensitiveness of the albumen. In the bright light of spring an exposure of two or three minutes with a pair of stereoscopic lenses will in general be amply sufficient. Experience alone can determine the amount of time required in a given case.

Development of the Image.

The plate is placed in a glass dish, or in one of gutta-percha, and the developer is poured upon it by the same mode of manipulation as just described to be used in the sensitizing operation.

Formula for the Developing Solution.

Gallic acid 8 grains.
Distilled water, (warm, 90°,) 2 ounces.

Previous to immersion in the above solution the plates are subjected to the softening action of a warm dilute solution of gallic acid (one grain to the ounce of distilled water) for half an hour. After this the plate is flowed with a sufficient quantity of the above solution containing five or six drops of a solution of nitrate of silver two per cent strong. the image will soon begin to appear, and will proceed until the vigor of the print is satisfactory. the development is not so soon complete as in collodion operations, the time required varying from a few minutes to forty minutes or an hour. Any amount of exposure almost can be made to yield a good picture by adapting the developing solution in accordance with the exposure. If the plate has been under-exposed more silver will have to be used; if over-exposed, less will be found to be all that is necessary. Silver from the sensitizing bath might be used, but in this case it must contain more acetic acid. the weak solution above described is to be preferred; and if there is a tendency to fogging, add a few drops of acetic acid to counteract the effect. As soon as the shades are sufficiently dense, the plate is removed from the bath, well washed in many waters, and then the image is fixed in a solution of hyposulphite of soda. No varnishing is required, because the albumen film is quite hard of itself.

Taupenot Process--Collodio-Albumen Process.

This process was originally proposed by Taupenot. His design was to combine the advantages of these two ingredients, albumen and collodion. the collodion film on the glass is a much better receptacle of the albumen than the glass itself; but the operation is somewhat circuitous, inasmuch as the plate is sensitized twice. Other methods have since been devised, in which the collodio-albuminous film requires but one sensitization. Some of these are found to be very effectual dry processes.

Preparation of the Glass Plates.

These are first immersed for a number of hours in the following solution:

Salts of tartar, 1 ounce.
Rain-water 16 ounces.

If the plates have been already employed before, soak them in water and remove the collodion film with a piece of rag. the alkaline solution can be used several times. As soon as the plates are removed from this solution, pass them through water several times, and then clean and polish them in the vice, by means of alcohol and rotten stone, as previously directed. Immediately before the collodion is flowed upon the plate, it is dusted with a silk cloth, and then with the broad camel's hair pencil. A collodion that flows well and one that adheres forcibly to the glass is to be preferred.

Formula for the Collodion.

Ether, (concentrated,) 12 ounces.
Alcohol, " 3 ounces.
Pyroxyline 1 drachm.
Iodide of ammonium 1 drachm.
Bromide of ammonium 15 grains.

This collodion, containing quite an excess of ether, which is very volatile, has to be poured over the plate with great dexterity. It is very fluid and admits of this dexterity. the plate is then, as soon as the film has sufficiently congealed, immersed in the ordinary nitrate of silver bath, containing about 35 grains of the nitrate to the ounce of distilled water. It is left in this bath for four or five minutes and then taken out and allowed to drain. After this proceeding, the plate is immersed in a dish of rain-water and well washed by agitation, or it may be washed at the tap in the ordinary method, and then flowed with distilled water several times, and again allowed to drain. It is next flowed, while still moist, with the following albuminous preparation:

The white of egg, (free from germs and yolk,) 12 ounces.
Distilled water 2 ounces.
Iodide of ammonium 44 grains.
Bromide of ammonium 16 grains.
Ammonia, 1 ounce.
White sugar 2 drachms.

These ingredients are intimately mixed by an egg-beater until the mass is reduced to froth. They are then allowed to subside for a day or two. the clear part is separated by decantation or by a syringe from the residue below, and from the indurated scum on its surface above. With this clear solution flow the still moist plate as you would with collodion almost. Holding the plate by the left-hand nearer corner, between the thumb and the first finger, pour the albumen on the right-hand further corner, then inclining the plate, let the albumen flow to the left-hand further corner. Now allow the whole body of the albumen to flow down in one mass, driving the water before it until it arrives at the nearest edge. Inclining the right-hand nearest corner, allow the water to flow off together with the excess or surplus of the albumen into a separate receiver. Now raise the nearest edge of the plate and let the surplus proceed back again to its place of starting, and once more to the nearest right-hand corner, when all excess is allowed to flow off. The plates are then reared away on one corner to dry. in this state the film is not sensitive, and consequently the plates so far can be prepared beforehand and preserved until wanted.

Sensitizing of the Taupenot Plates.

Nitrate of silver 1 ounce.
Acetic acid 1 ounce.
Nitrate of silver 12 ounces.

The plates are immersed in this bath with great care and dexterity, in order to avoid all lines of stoppage, etc. in thirty seconds the film will be sufficiently sensitized. the plate is then taken out and plunged into a dish of water, moved about in this, then transferred to another, allowed to drain, finally flowed two or three times with distilled water, and put away to dry in a perfectly dark place.

In this condition the film is much more sensitive to light than albumen alone, although it is less so than collodion. Time plates can be preserved sensitive for several months, but the sensitiveness gradually deteriorates by age.


With a portrait combination an exposure of two or three seconds will be found to be sufficient to receive a good impression of an object well illumined by the sun, and as many minutes will suffice with a single lense.

Development of the Image.

The developing solution is composed as follows:

Distilled water 12 ounces.
Gallic acid, 18 grains.
Pyrogallic acid, 6 grains.
Alcohol 2 drachms.
Acetic acid ½ drachm.

To every three ounces of this solution add a solution of one grain of nitrate of silver, when about to use it. A larger proportion of pyrogallic acid and nitrate of silver will increase the intensity of the blacks; and where the time of exposure has been too long, the gallic acid may be diminished and the acetic acid increased. the horizontal bath is preferable for this sort of development. the plate, first dipped in water, is then lowered dexterously with the collodio-albumen surface downward into the solution, and the upper end is allowed to rest on a piece of glass or porcelain, to prevent the film from coming in contact with the bottom of the vessel. the plate is raised from time to time to watch the progress of the development, which may occupy from ten minutes to twenty-four hours. When the shades are intense enough, the plate is taken out, well washed, and then immersed in the fixing solution.

Fixation of the Taupenot Plates.

Hyposulphite of soda 1 ounce.
Water 20 ounces.

Even a weaker solution will frequently be all that is required. the soluble iodides being removed, the plates are taken out and thoroughly washed as usual.

Modified Albumen Process. (By James Larpey.)

Let the plates be coated with any collodion, iodized or non-iodized, and afterward well washed. Flow them with the albumenizing solution, which is made as follows:

Formula for Iodized Albumen.

Albumen 10 ounces.
Iodide of ammonium 50 grains.
Bromide of potassium 12 grains.
Water 2½ ounces.

The mode of flowing is the same as already described for the Taupenot process. After draining, dry as before indicated.

Sensitizing Solution.

Nitrate of silver 60 grains.
Acetic acid 60 minims.
Water 1 ounce.

The time required will be thirty seconds or thereabouts; remove from the bath and wash thoroughly.


This preparation requires about twice as long an exposure as wet collodion.


Saturated solution of gallic acid and a few drops of a solution of nitrate of silver, (fifty grains to the ounce of water.) By varying the quantity of nitrate, any kind of tone can be got. A small quantity yields brown tones; a larger quantity black tones.


Wash thoroughly and then fix in the ordinary solution of hyposulphite of soda; finally wash and dry.

The collodion film in this process facilitates the flowing of the albumen, which besides dries much quicker. Its keeping properties are very good.

Modified Collodio-Albumen Process. (By James Mudd.)

Coat the plates with collodion, as usual. As soon as the film is sufficiently adhesive, immerse in the ordinary bath of nitrate of silver. Dilute the collodion with ether if it gives a very thick and creamy film. After sensitizing, wash the plates thoroughly, and then immerse them in a weak solution of iodide of potassium, (one grain to the ounce of water,) for two or three minutes, moving them gently all the while. Wash again and allow to drain for one minute.

Formula for Iodized Albumen.

Albumen 10 ounces.
Iodide of potassium 50 grains.
Bromide of potassium 10 grains.
Ammonia, 100 minims.
Water 24 ounces.

First dissolve the iodide and bromide in the water, then add the ammonia; mix this solution with the albumen, and beat the whole into a froth, and then allow it to settle for at least twenty-four hours. Decant, as previously directed, before use. While the plate is still wet, pour on the albumen. Pour it on and off twice. Allow the plate to drain for a few minutes; then dry it rapidly before a clear fire, and make it quite hot.

Sensitizing Solution.

Nitrate of silver 40 grains.
Glacial acetic acid ½ drachm.
Distilled water 1 ounce.

Warm the plate slightly, and then immerse it in this Solution; drain for a moment, and wash in different dishes of pure water, and finally under the tap. Dry the plates by artificial heat, or let them dry spontaneously.

Plates so treated are very sensitive, and possess tolerable keeping properties. in summer, however, it is advisable to prepare fresh ones every two weeks or so.


The plate, first moistened and supported on a horizontal stand, pour upon it a fresh solution of pyrogallic acid, (three grains to the ounce of water.) the image will soon appear, but it requires intensity.


Pyrogallic acid, 2 grains.
Citric acid 2 grains.
Nitrate of silver solution, (20 gr. strong,) 2 or 3 drops.

Pour a sufficient quantity of the above upon the plate and keep it in motion. If the shades do not assume sufficient intensity, use more silver. the solution may be warm in cold weather, or when the picture has been under-exposed.

Fixing Solution.

Hyposulphite of soda, 6 ounces.
Water 16 ounces.

Wash the plates well before immersion; fix as usual, and again wash. Cyanide of potassium must not be used for this purpose.

Fothergill Process.

This process, like the two preceding, is a mere modification of the Taupenot process, the principal difference between this and the Taupenot being that the plate is sensitized only once. the plate is first flowed as usual with any ripe bromo-iodized collodion, and then as usual sensitized in the common nitrate of silver bath; after removal from the bath, soak the plates in distilled or rain-water, so as to remove all but a mere trace of nitrate of silver. This part of the operation is probably the most important and characteristic of the operation. Some pursue the plan of soaking the plates, as just directed, in a dish of distilled water, keeping the water moving over their surface until all apparent oily streaks or greasiness have disappeared. Others recommend a more definite plan. They use a measured quantity of distilled or rain-water for a certain number of square inches of surface. for a stereoscopic plate half an ounce of water is poured carefully on one corner of the plate, and is made to cover the whole quickly, as in the developing process. the water is then kept in motion by tilting the plate slightly up and down, until the greasiness disappears; it is then poured off, and the plate is allowed to drain for a moment, and covered with the following preservative solution:

Albumen 2 ounces.
Ammonia, 20 minims.
Water, 6 ounces.

Mix well by agitation in a large bottle, and filter through a sponge immediately before use.

This solution is poured upon each plate whilst still moist, in the same manner as plates are covered with collodion; the residual quantity is poured off at one of the near corners. Another quantity of the albumen is now poured upon the plate and allowed to remain one minute, after which it is poured off, and the plate is properly washed, drained, and dried either spontaneously or by the application of heat.

Developing Solution.

After exposure, the plates are first moistened in distilled water, and then covered with the following developer:

Pyrogallic acid 3 grains.
Citric acid, 1 grain.
Water 2 ounces.
Alcohol, 10 minims,

Add to each ounce of the above solution half a drachm of a solution of nitrate of silver, containing fifteen grains to the ounce of water. Wash thoroughly when the image is perfect.

Fixing Solution.

Fix the impressions in a bath of hyposulphite of soda; wash, dry, and varnish.