CHAPTER VI.
PRINTING PROCESS--SALTING PAPER--SILVERING PAPER--PRINTING THE POSITIVE--FIXING AND COLORING BATH--MOUNTING THE POSITIVE.
The Printing Process.
[Sidenote: MANIPULATIONS OF 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.
Water 1 quart. Muriate of ammonia 65 grains.
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 1-1/2 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:--
Water 2-1/4 ounces. Nitrate of silver 75 grains.
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.
Solution of chloride of gold, a quantity equivalent to 4 grains. Nitrate of silver 30 " Hyposulphite of soda 2 ounces. Water 8 "
"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:--
Gum arabic 2 ounces Gum tragacanth 1-1/2 " Isinglass 1-1/2 " Sugar 1/2 " Water 3 pints
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:--
Water 8 ounces. One table spoonful of wheat flour Powdered alum 40 grains. Powdered resin " Brown sugar 1 ounce. Bichloride of mercury 20 grains.
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.
=FACTS WORTH MENTIONING.=
[Sidenote: FACTS WORTH KNOWING.]
_The Poisonous Effects_ of cyanide of potassium upon sores, may be obviated by immediately applying some of the positive developing solution, described at page 62. By this means much annoyance may be avoided to persons afflicted with chapped or sore hands.
_Bending Glass Rods_ or tubes can be easily done by subjecting them to the blaze of a spirit lamp--the same as that used for gilding the daguerreotype. First hold the rod just above the blaze, then gradually allow it to descend into it, imparting to the rod a rotatory motion with the finger and thumb: this will soon cause a softening of the glass, when it may be bent to any desired shape. If the ends are to be bent to form hooks, another small piece of glass, or any warm metal, may be placed upon the end, in the blaze of the lamp, and as soon as thoroughly softened, it can be pressed or bent to form the hook. By filing around a glass tube or rod, it may be easily and safely broken at the desired point, by giving it a sudden jerk between both hands, holding it close to the encircled part.
_Cementing Glass_ may be readily accomplished by placing the two ends together in the blaze of the lamp, and holding them there until they attain a sufficient degree of heat to slightly fuse: when cool, the ends will be found perfectly united.
_The Background_ best adapted to positives is unbleached muslin, such, as is sold for sheeting, and can be found in almost any dry goods' store: it should be from two to three yards wide. A clouded appearance is given to the background by merely marking it with _charcoal_, forming streaks or "_waves_" resembling clouds. These come out black, or dark, in the positive, and give a variegated appearance. The roughness of the marking does not matter, since the background is generally a little out of the focus of the lenses. Trees and other designs may be represented in this matter.
_Positive Collodion Pictures_ may be whitened by the use of bichloride of mercury, thirty grains to one ounce of water. After the picture has been developed, fixed and washed, by the process given in the preceding pages, the solution of bichloride of mercury may be poured over the surface of the image: it almost immediately presents a series of interesting changes in color. The surface at first blackens but for a few minutes, when it begins to get lighter, and gradually brightens to a pure white, inclining to a blue. It should then be thoroughly washed and dried, as usual.
_Instantaneous Pictures_ may be taken by employing the _iodide of iron_ in the collodion. The best method with which I am acquainted, is to have a saturated solution of iodide of iron in alcohol, and drop one or two drops into an ounce of the collodion (which has been previously iodized) used in taking positives. This can be used at once, as soon as mixed. No more of this collodion should be prepared than is wanted for immediate use, as it will keep good for only a few hours. The saturated solution of iodide of iron can be kept on hand ready for use at all times. There should be an excess of the iodide in the alcohol. The same accelerating effect is produced with the negative collodion prepared in this way.
_Plain Collodion_ may be iodized as soon as dissolved: this will save time in settling. It is a fact that some cotton is more readily dissolved when the bromo-iodizing is present: but by the addition of this, I have often taken up considerable quantities of the gummy sediment remaining in the bottom of bottles.
_Prepared Glass_ may be preserved clean and free from dust by keeping in boxes such as those used for keeping daguerreotype plates. By taking out every other partition between the grooves, the glass can be readily put in.
_Collodion Vials and Bottles_, after having collodion in them once, should be rinsed with alcohol and ether (in the same proportions as employed for dissolving the cotton), before using them a second time for that purpose. Penuriousness in this respect would be bad policy.
_Coating Large Glasses._--A convenient method of doing this is represented in the following illustration:
The glass is held by one corner, 2; the other corner, 4, is rested on a table or bench, and the collodion poured on, so that the excess may be poured off at 1.
_Black Stains_ upon the hands, caused by nitrate of silver, may be removed by moistening them and rubbing with a lump of cyanuret of potassium. This salt is poisonous, if used to a great extent [_See page 139_]. Another safer, but more expensive plan, however, is to take a saturated solution of iodide of potassium in water, and then wash with nitric acid diluted with two parts water.
_Stains upon White Linen_ can be removed by washing with a saturated solution of iodide of potassium containing a little iodine; then wash with water, and soak in a saturated solution of hyposulphite of soda until the yellow iodide of silver is dissolved.
_The hands_ should always be washed after fixing a positive or negative picture, before again touching a glass to be coated, or the dipper; this precaution is necessary, lest any of the iron salt, or the hyposulphite, should get into the silvering solution and spoil it.
_In taking Collodion Pictures_, it is always advisable for the sitter to be arranged before the glass is taken from the bath: this will save time and there will be less liability of the collodion drying.
_A Good Negative_ may be known by its possessing the following characteristics:--By transmitted light the figure is bright, and appears to stand out from the glass; the dark shadows are clear, without any misty deposit of metallic silver; the high lights black almost to complete opacity.
_A Glass Coated with Collodion_, if kept too long before immersion in the bath, will not be equally sensitive over its surface; the parts most dry being the least sensitive.
_Glass Pans, for Scales_, can be procured by every one at trifling expense: Take a watch crystal, and place in the common metal pan; balance this with lead, or any weight: this can easily be kept clean, and is the most advisable for weighing all deliquescent salts, and chemicals employed in the collodion process.
_Caution._--Persons engaged in making collodion, and using ether and alcohol, must bear in mind that these chemicals are _very inflammable_; hence extreme caution is necessary to avoid exposing them to the flame of a lamp or candle. I have known of several serious accidents, of recent date, all of which were caused by the imprudence of the experimenter in the particular above mentioned.
_Wipe the Plate-holder_ every time before the glass is put into it: this will prevent spots, which might otherwise occur from the presence of nitrate of silver solution which drained from the plate previously used. These spots are of an opaque yellowish tinge, and in shape resemble the stain which would be occasioned by a _splash_ of water.
_Glass jar Positives._--A good _white_ or light-green glass will answer for the collodion coating. Glass which contains air-spots can be used, if it be placed in such a manner as to let the light of the image come over them, as the spots cannot be seen through the opaque surface. Only the best white glass should be used for _covering_ the picture. Some operators use the convex glass, which is very clear, and answers the purpose.
_The Nitrate of Silver Bath_ should be kept covered, except when in use.
_If a Glass be Immersed too soon_, streaks and waves will be occasioned. These will be seen at the end of the plate which is least dry: the coating is also more liable to peel off. It should be borne in mind, however, that the peeling of collodion is not always attributable to this cause.
_Diffused Light in the Developing Room._--In proportion as the sensitiveness of the plates increases, greater care must be exercised in thoroughly excluding all rays of white light. With opalescent films, neutral, this cause of fogging is more common than any other.
_Tn the case_ of a portrait, if the features have an unnaturally black and gloomy appearance, the dark portions of the drapery, &c., being invisible, the picture has been _underexposed_ in the camera.