The Printing Process.

There is probably no department of the photographic art where can be found an equal amount of variety, as regards chemicals, manipulations, etc. The course adopted in the commencement, of giving only one process for the operator to work by—and that a good one—will be strictly adhered to in this place. I have produced as good positives on paper by the following plan, as I have ever seen. Should the reader wish more extensive acquaintance with the printing processes, he is referred to Humphrey's Journal.

Salting Paper.

The water is put into a flat, gutta-percha, glass, or earthen dish, and the muriate of ammonia is put into it, and stirred until it is dissolved and is well mixed with the water; then proceed as follows: we will suppose we have a gutta-percha dish sufficiently large to take in a sheet of paper 8 by 10 inches, and about 1½ or 2 inches deep: take hold of two corners of the paper with the thumb and finger of each hand, and then draw the paper through the solution, by passing it from one end of the dish to the other, so that it will be wetted on both sides; then turning it over in the same manner, draw it back, so that its surface will be thoroughly moistened, but it is not necessary to saturate the paper. Now the paper is ready for drying, which may be done by hanging it on the edge of a shelf by means of little tack nails put through it at the same corners by which it was held in passing through the salting solution. In order to prevent streaks, from forming upon the paper, it is better to hang it in such a manner that it cannot touch the shelf, except at the corners: say the sheet is eight inches wide, and the tacks (which are put through the corners) to be only five or six inches apart, this will give the proper bend outwards, preventing its contact with the shelf. This entire operation can be performed in daylight, or otherwise as suits the convenience of the operator.

This paper, when dry, should be laid between the folds of blotting paper (filtering paper will answer), and may be kept for any length of time, and is ready for the silvering process.

Silvering Paper.

In silvering paper, I employ the ammonio-nitrate, which is prepared as follows:—

Dissolve (in a 4-ounce vial) the nitrate of silver in the water, and then pour one-fourth of the solution into an ounce graduate or any convenient vessel: this keep for farther use in preventing the presence of an excess of ammonia. Now, into the bottle containing the three-fourths put about 4 drops of aqua-ammonia; shake well and a brown precipitate will be given. Continue adding the ammonia, drop by drop, and shake after each addition, until the brown precipitate is re-dissolved and the solution is clear; then pour back into the bottle the one-fourth taken out at first: this will leave the solution slightly turbid, and when so, there is no excess of ammonia which would be objectionable. It may now be filtered through filtering paper, and it (the clear liquid) is ready for use. This should be kept in the dark, as it decomposes rapidly when exposed to light.

The method of silvering the paper with ammonio-nitrate of silver, is as follows: take a tuft of clean cotton, roll it into a ball-shape, then wet it by holding it against the mouth of the bottle containing the ammonio-nitrate, and when well wet, apply it to the paper (which should be placed flat on a clean board) by gently rubbing it over the surface, care being taken not to roughen it.

If the solution has not been filtered for some time, it would be advisable to pour a little on the centre of the paper, and then distribute it over the surface by means of the cotton, which is held in the fingers: by this last method any sediment which may be in the bottom of the bottle is prevented from getting upon the paper, and causing spots.

I have used a brush for the purpose of distributing the solution, by which plan there is less liability of getting it on the fingers and staining them. Care must be taken to cover the entire surface of the paper, or there will be light streaks, occasioned by the absence of the silvering solution.

This want of silver will appear on the paper in light parts, as seen in the accompanying cut:

After the paper has been perfectly coated, or washed with the silvering solution, it should be placed in a perpendicular position to dry. I usually tack the paper on a board of the requisite size, and then stand it on one edge until it has drained and dried. As soon as dry, it is ready for use. This paper will not keep more than twelve hours, therefore the operator should silver in the morning the quantity required for the day. It is imperatively necessary that the silvered paper be kept in the dark. It is extremely sensitive to light, and a very brief exposure of the prepared sheet would render it unfit for use.

Printing the Positive.

The several kinds of apparatus used for holding the negative and the sensitive paper together, have already been given on page 36, Figs. 31, 32, 33. The paper having been salted and silvered, as just described, should be placed on the pad of the printing frame or glasses, with its sensitive surface up, and then the negative placed directly upon and in contact with it; then it is to be fastened together, when it will be ready for exposure to the direct rays of the sun. From 10 to 40 seconds will be found enough to give a sufficiently intense print.

The paper first changes to a slate color, and then to a brown or copper color t when of a dark slate color is about the proper time to take it out and immerse in the toning bath.

Fixing and Coloring Bath.

I have employed the proportions given by Mr. Hardwich in his Photographic Chemistry, page 209—Humphrey's American edition.

"Dissolve the hyposulphite of soda in four ounces of the water, the chloride of gold in three ounces, the nitrate of silver in the remaining ounce; then pour the diluted chloride by degrees into the hyposulphite, stirring meanwhile with a glass rod; and afterwards the nitrate of silver in the same way. This order of mixing the solution is to be strictly observed; if it were reversed, the hyposulphite of soda being added to the chloride of gold, the result would be the reduction of metallic gold. The difference depends upon the fact that the hyposulphite of gold which is formed is an exceedingly unstable substance, and cannot exist in contact with unaltered chloride of gold. It is necessary that it should be dissolved by hyposulphite of soda immediately on its formation, and so rendered more permanent by conversion into a double salt of soda and gold.

"The time of coloration depends much upon the quantity of gold present, and may in some cases be extended to many hours. The results of a few experiments, performed roughly, appeared to indicate that the activity of this bath is less affected by depression of temperature than those prepared with tetrathionate. Certainly the injurious effects of prolonged immersion are not so evident as with the first two formulÆ: the purity of the whites remains unaltered for many hours if the bath is new, but with an old bath there is a tendency to yellowness, which is probably caused by the presence of sulphuretted hydrogen. Fresh chloride of gold must be added from time to time, as it appears to be required."

After the impression has remained in the toning bath a sufficient length of time, it should be placed in a dish or sink of clean water, which should be changed several times—floating for at least 12 hours; then it may be taken out and hung up to dry.

"Touching."—The coloring of a photograph forms no part of my process: this is a matter to be given into the hands of an artist, and when it bears the finishing touch of his skill, it is no longer a photograph, but an oil or watercolor painting; all the delicate workings of nature having been lost or hidden under the colors.

A photograph may often be "touched" to advantage. If, as is frequently the case, there be little white spots on the face of the paper, they may be readily covered by the application of a little India ink, with the point of a wet pencil or fine small brush.

Mounting of Positives.

This, though a small matter in itself, is worthy of great attention. The durability of the proof depends much upon the purity of the paste used in causing its adhesion to the Bristol board. I have employed the following composition with the most eminent success:—

These ingredients should all be dissolved, and then boiled down to the proper consistency, by means of a gentle heat.

I will give another composition, which will serve a good purpose, and keep for a long time:—

This last composition may be more convenient for operators, and it will answer the purpose well. It is thought by some to be the best and most durable paste yet prepared for the purpose.