LEWIS'S PATENT VICES FOR HOLDING THE GLASS—CLEANING AND DRYING THE GLASS—COATING—EXPOSURE IN THE CAMERA—DEVELOPING—FIXING OR BRIGHTENING—BACKING UP, &C.
Manipulations.
MANIPULATIONS.
Under the head of manipulations I give the method I employ, and avoid confusion by omitting all comments upon the thousand suggestions of others.
The glass is to have its sharp edges and corners removed, by drawing a file once or twice over it. The article used for holding the glass is called a vice. This vice is firmly secured to a bench.
[Since the foregoing pages have been in type there has been introduced into market a new patent vice, adopted both for glass and plate blocks. I find it, although a little more expensive, an article better suited to the wants of the operator or amateur. It is called Lewis's Patent Glass Vice.]
Clasp the glass firmly in the vice, and pour orspurtupon it a little alcohol and rotten stone, previously formed into a paste, and then, with a piece of cotton flannel, the same as used in the daguerreotype, rub the glass until it is perfectly cleansed from all foreign substances, which will soon be known by experience. The rotten stonepaste should not be allowed to dry while rubbing, as it is more liable to scratch the glass. I use another small bottle containing clear alcohol, which I spurt upon the glass, to obviate the drying.
When the glass has been sufficiently cleaned, it should, while wet, be put in a vessel of water for future rinsing. Clean, as before, as many plates of glass as may be required, and when enough are ready, rinse them off in the water, and then in a quantity of clean water, or a running current, give them a second thorough rinsing, and set them aside to drain.
A convenient method of doing this, is to drive two nails horizontally into the wall or partition, a sufficient distance apart (say about 2½ inches) for the glass to rest on: the upper corner of the glass should be placed against the wall, and the extreme lower diagonal corner left hanging between the nails—which will probably be found the best position for draining yet suggested.
After drying, they may be put into a box for safe and clean keeping. Particular caution is necessary to avoid handling the glass during the operation. I never take the glass between my fingers, so that they come in contact withboth sidesof it, except at one particular corner, as at Figs. A and B. A quantity of glass prepared as above, may be kept on hand for use two or three days, and when wanted they should be again put into the vice[C]andcleaned, first with cotton flannel wet with alcohol, and then with dry flannel; and then, at a temperature slightly above that of the surrounding atmosphere, except in cases where the thermometer stands above 70°, it is ready for the brush,[D]which should be carefully applied to each surface, to free it from all particles of dust, and then it is ready for the film of collodion.
[C]The vice should be thoroughly cleansed, and no particles of rotten stone, or other matter, be allowed to come in contact with the glass, as it might adhere to the edges and wash off into the silvering bath, and ultimately cause specks. Always remember that cleanliness is an indispensable requisite in order to produce a good picture.
[C]The vice should be thoroughly cleansed, and no particles of rotten stone, or other matter, be allowed to come in contact with the glass, as it might adhere to the edges and wash off into the silvering bath, and ultimately cause specks. Always remember that cleanliness is an indispensable requisite in order to produce a good picture.
[D]One of the most desirable articles I have found for this purpose is the wide (3 inch) flat camel's-hair brush often called a blender.
[D]One of the most desirable articles I have found for this purpose is the wide (3 inch) flat camel's-hair brush often called a blender.
Fig. A. Fig. B.
Fig. A. Fig. B.
The glass is held between the thumb and forefinger of the left hand by the corner 1, Fig. A., 3 and 4 towards and nearest the body, and as nearly level as possible. I find this the best position to hold the glass; as, in the case of the larger ones, they can be rested on the end of the little finger, which should be placed as near the edge as possible. Then, from the collodion vial, pour on the collodion, commencing a little beyond the centre and towards 1, continuing pouring in the same place until the collodion nearly reaches the thumb—the glass slightly inclined that way; then let the glass incline towards 4, and continue to pour towards 2.
As soon as enough has been put on to liberally flow the glass, rapidly and steadily raise corner 1, and hold it directly over 3, where the excess will flow oil into the mouth of the vial, which should be placed there to receive it. In case of a speck of dust falling at the time of coating, it can often be prevented from injuring the surface by changing the direction of the flowing collodion, so as to stop it in some place where it will not be seen when the picture is finished. Now, with the thumb and finger of the right hand, I wipe off any drops or lines of collodion that may be found upon theouteredge or side of the glass, being careful not to disturb that connected with the face.
When the coating has become sufficiently dry, so that when I put my finger against it, it does not break the film, but only leaves a print, I put it into the silvering bath [seeFig. p. 34]. I generally try corners 2 and 3. The time, from the first commencement of pouring on collodion to its being put into the bath, should not exceed about half a minute, at a temperature of 60°. The finger test is the best I have found. The glass is to be rested on a dipper [seeFig. p. 34], and placed steadily and firmly into the nitrate of silver bath—this in a dark room. It should not be allowed to rest for an instant as it is entering the solution, or it would cause a line. The time for the glass to remain in the bath depends upon the age and amount of silver the bath contains; for a new solution, fromtwotothreeminutes will be sufficient to give the proper action. If it be old, three to five minutes will be better. When it is properly coated, it can be raised up and taken by the corner, and allowed to drain for a few seconds, and then should be placed in the tablet, and is ready for the camera. The time of exposure will dependupon the amount of light present. If the bath is newly mixed, and the collodion recently iodized, it should produce a sufficiently strong impression by an exposure of about one-third of the time required for a daguerreotype. If the collodion has been iodized some time, and the bath is old, about one-half of the time necessary to produce a daguerreian image will be required.
The plate should in no case be allowed to become dry from the time it is taken from the bath up to the time of pouring on the developer. At a temperature of about 70°, I have had the glass out of the bath ten minutes without drying. After exposure, the glass should be taken again into the dark room, and removed from the tablet and held over a sink, pail, or basin and the developing solution poured on it as follows: hold the glass between the thumb and finger of the left hand, by the opposite end corner from that in coating with collodion,i. e., 2, and let 3 and 4 be from you.
MANIPULATIONS OF THE POSITIVE PROCESS.
Commence pouring on the developing solution at the end by the thumb, and let it flow quickly and evenly over the entire surface, the first flooding washing off any excess of nitrate of silver there may be about the edges or corners of the glass (if this silver is not washed off, it flows over the edges and on the surface of the impression, producing white wavy clouds of scum), and then hold the glass as nearly level as possible, it having upon its surface a thin covering of solution (care should be observed not to pour the developing solution on the plate inone place, as it would remove all the nitrate of silver and prevent the development of the image, leaving only a dark or black spot where it is poured on). Put down the bottle containing the developing solution, and take up a quartpitcher previously filled with water, and as soon as the outline of the image can be plainly seen by the weak or subdued light of an oil or fluid lamp or candle, pour the water over copiously and rapidly. Continue this until all the iron solution has been removed. If this is not done, the plate will be covered with blue scum on the application of the washing solution. Then the glass can be taken into a light room, and the iodide of silver coating washed off with the cyanide solution, and then rinsed with clear pure water, and stood in a position to drain and dry. I place a little blotting paper under them: it aids in absorbing the water, and facilitates the operation.
Place the face of the glass against the wall, in order to prevent dust from falling upon it. I have often dried the coating by holding or standing the glass adjacent to a stove. A steady heat is advisable, as it leaves the surface in a more perfect state, and free from any scum. After the coating is perfectly dry, it is ready for the preserving process. It should be warmed evenly, and when about milk warm, "Humphrey's Collodion Gilding" is poured on the image in precisely the same manner as the collodion. In a few seconds the coating sets, and after three-quarters of a minute, if it has not become dry, the blaze of a spirit lamp may be applied to the back and it will immediately becomeperfectly transparent, and nearly as hard as the glass itself: the effect is fully equal, if not superior, to that of chloride of gold in gilding the daguerreotype image. The surface becomes brilliant and permanent. The back of the glass can now be wiped and cleaned with paper or cloth, and gently warmed, and then with a common small brush one coat of black varnish can be applied. This brush should be drawn from side to sideacross the glass, and on the side opposite to that which has received the image.
This is in order not to make streaks in the coating of varnish, but to have uniform lines across the entire length or breadth of the glass. If the varnish is of the proper consistency, it will flow into a smooth, even coating. After this first coating is dry, apply a second in the same manner, only in an opposite direction, so as to cross the lines of the first, uniting at right angles; when this last coating is very nearly dry, a piece of paper, glazed black on one side, and cut to the proper size, can be put next the varnish; it gives it a clean finish, at the same time that it aids towards a dense blackening.
I sometimes apply the black varnish by flowing, in the same manner as in putting on the collodion.
This picture is to be colored and put up in the same manner as the daguerreotype image, with a mat and glass. The last glass may be dispensed with by first using the collodion gilding, and then upon its surface apply the black varnish, as before. In this case the image is seen through the same glass it is on, and without being reversed: in this case the mat goes on the outside of the glass.
When the image is seen through the glass upon which it is taken, it cannot be colored with very great success, as it cannot be seen through the reduced silver forming it. This forms a more or less opaque surface; but in point of economy the single glass is preferable. Yet I would not recommend such economy, for I consider that a good impression ought to be well put up, and the welfare of the art fully substantiates that consideration.
Many ways have been devised for putting up pictures I have produced pleasing effects upon colored glasses: forinstance, a picture on a light purple glass has a very pleasing effect; also in some other colors. I have also used patent leather for backing the image.
I have produced curious and interesting results by placing a piece of white paper, or coloring white the back of thewhitesof the image, and then blackening over or around this. By this means the whites are preserved very clear.
Positives for Pins, Lockets, etc.—I employ mica for floating the collodion on, as it can be as easily cut and fitted as the metallic plate in the daguerreotype; and positives taken upon fine, clear, transparent mica, are fully equal to those taken upon glass, and yet they are ambrotypes.
Mica is an article familiar to every one, as being used in stoves, gratings, etc.
The method of using it, is to take the impression on a thick piece, and then split it off, which can readily be done in the most perfect, thin, transparent plates; it is equally as thin as tissue paper, and can be cut as easily. The thickness of the piece upon which the impression is taken is of no moment, since it can be reduced at pleasure and is more easily handled while thick.
Observations on the Positive Collodion Process.
Fogging.—There are numerous causes which will produce fogging: the principal ones will be mentioned. One is the admission of light upon the collodion. This maybe from a want of closeness of the dark room, the tablet,[E]the camera, or by accidental exposure. The method to locate the particular cause is to,first, when the glass istaken from the nitrate bath, let it stand for sufficient time to drain, then pour on the developer, and if the coating assumes a mistiness, or light-grey color, the fault is in the dark room; again, if the plate, after it has been treated with the developer and fixed, is clear, then also the fault is there. Now try the tablet in the same manner, and if not there, try the camera, and the proper location will be found.
[E]Since the foregoing pages have been in type an entirely new feature in the line of apparatus has been introduced; this is W. & W. H. Lewis's Patent Plate-holder with solid glass corners. These Holders have every requisite for excluding the light from the sensitive surface; they are accompanied with a "shut off," so that when the slide is drawn no light can reach the glass. This, in connection with the unequalled advantage of the solid corners, makes them the most desirable article for the Operator.Humphrey's Journal, in referring to these Holders, says:—"We are always glad to note every step which our mechanics make towards improvement on the apparatus used by our practical photographic operators, and make the present announcement of one which has only to be known to be readily understood, and to be seen to be appreciated. A patent has recently been granted for making solid glass corners, which are to be attached to plate-holders, and form the most perfect article that has ever been introduced. Heretofore the operator has had the corners of his plate-holders made with separate pieces of glass, cut so as to fit the corners of his frames; these are only glued or grooved in, and are constantly coming apart, falling out, and annoying in many ways; for our part, we never have considered them as fit for use in any manner. We look upon the present improvement as destined to entirely supersede all the methods heretofore introduced. In this case the collodionized or albumenized plate can come in contact with no other substance than a single piece of glass, and consequently there is far less liability of accident from either the staining of the plate or breaking of the holder. The rapid favor this improvement has gained already shows its great advantage over all other methods heretofore employed."
[E]Since the foregoing pages have been in type an entirely new feature in the line of apparatus has been introduced; this is W. & W. H. Lewis's Patent Plate-holder with solid glass corners. These Holders have every requisite for excluding the light from the sensitive surface; they are accompanied with a "shut off," so that when the slide is drawn no light can reach the glass. This, in connection with the unequalled advantage of the solid corners, makes them the most desirable article for the Operator.Humphrey's Journal, in referring to these Holders, says:—
"We are always glad to note every step which our mechanics make towards improvement on the apparatus used by our practical photographic operators, and make the present announcement of one which has only to be known to be readily understood, and to be seen to be appreciated. A patent has recently been granted for making solid glass corners, which are to be attached to plate-holders, and form the most perfect article that has ever been introduced. Heretofore the operator has had the corners of his plate-holders made with separate pieces of glass, cut so as to fit the corners of his frames; these are only glued or grooved in, and are constantly coming apart, falling out, and annoying in many ways; for our part, we never have considered them as fit for use in any manner. We look upon the present improvement as destined to entirely supersede all the methods heretofore introduced. In this case the collodionized or albumenized plate can come in contact with no other substance than a single piece of glass, and consequently there is far less liability of accident from either the staining of the plate or breaking of the holder. The rapid favor this improvement has gained already shows its great advantage over all other methods heretofore employed."
"We are always glad to note every step which our mechanics make towards improvement on the apparatus used by our practical photographic operators, and make the present announcement of one which has only to be known to be readily understood, and to be seen to be appreciated. A patent has recently been granted for making solid glass corners, which are to be attached to plate-holders, and form the most perfect article that has ever been introduced. Heretofore the operator has had the corners of his plate-holders made with separate pieces of glass, cut so as to fit the corners of his frames; these are only glued or grooved in, and are constantly coming apart, falling out, and annoying in many ways; for our part, we never have considered them as fit for use in any manner. We look upon the present improvement as destined to entirely supersede all the methods heretofore introduced. In this case the collodionized or albumenized plate can come in contact with no other substance than a single piece of glass, and consequently there is far less liability of accident from either the staining of the plate or breaking of the holder. The rapid favor this improvement has gained already shows its great advantage over all other methods heretofore employed."
"Decomposition by exposure to light or by long keeping, even in the dark. The author conceives that it is possible for organic matter alone to produce, after a time, a partial decomposition of solution of nitrate of silver, sufficient to prevent it from being employed chemically neutral, but probably not much interfering with its properties in other respects.
"Use of rain water or of water containing carbonate of silver being perfectly neutral and from nitric acid. This difficulty is not a theoretical one only, but has actually been experienced. Rain water usually contains ammonia, and has a faint alkaline reaction. Pump water often abounds with carbonate of lime, much of which, but not the whole, is deposited on boiling. To remove the alkaline condition, add acetic acid, one drop to half a pint of the solution.
"Partial decomposition of the bath, by contact with metallic iron, with hyposulphite of soda, or with any developing agent, even in small quantity. Also by the use of accelerators, which injure the bath by degrees, and eventually prevent its employment in an accurately neutral state.
"Vapor of ammonia, or hydrosulphate of ammonia, escaping into the developing room."
Spots.—One principal cause of spots isdust. The operating room should be kept as free from this as possible, and instead of its being dusted, it should be wiped with a damp cloth. Specks or flakes of iodide of silver are often found in the nitrate bath. These sometimes occur by an ever-iodized collodion, and sometimes by collodion falling off while being silvered. When this occurs, the nitrate of silver solution should be filtered. A new sponge or a tuft of cotton is a good article to filter nitrate of silver solution through. A small particle of light finding its way upon the plate, will produce a spot. Another and very frequent cause is, putting the slide of the tablet down rapidly, causing it to spatter upon the plate the solution which has drained off from it. This paper will be opaque when viewed by reflected light, and dark when viewed by transmitted light. Occasionally a sort of transparent spot will appear: this may be traced to a want of sensibility of the iodide of silver. Large transparent spots frequently appear by the operator's pouring the developing solution upon one place, and washing off the small quantity of nitrate of silver necessary to develope the image. This will be easily detected, and can be obviated byfloodingthe most of the surface of the glass with a steady stream of the developer.
Stains and Lines.—If the glass be allowed to rest for an instant with one portion of its surface in the silvering solution and the other out of it, it would cause a streak across; hence the necessity of totally immersing it with one firm, steady motion removing the glass before it has been thoroughly wetted, and the ether and alcohol allowed a uniform action over the entire surface. A plate shouldnot be disturbed in the bath until it has been in a full minute at least.
Irregular Linesare often caused by using the developing solution too strong, or by not pouring it evenly over the plate at once. Should it be allowed to rest in its progress, if but for an instant, it will leave its line. Sometimes spangles of metallic silver appear: these are caused by the presence of too much nitric acid in the developer for the proportion of iodide in the film and the strength of the bath.
There are other phases connected with the practice of the positive process, which it would be almost impossible to commit to paper, and cannot be so explained as to be perfectly comprehended by the new experimenter. It is absolutely necessary for all to observe every little point noticed in the foregoing pages, and at the same time exercise some good judgment, and no one need hesitate through fear of not being successful.
PRACTICAL DETAILS
OF THE
NEGATIVE PROCESS.
NEGATIVE PROCESS—SOLUBLE COTTON—PLAIN COLLODION—DEVELOPING SOLUTION—RE-DEVELOPING SOLUTION—FIXING THE IMAGE—FINISHING THE IMAGE—NITRATE OF SILVER BATH.
Negative Process.
The manipulations and chemicals employed in the production of the negative collodion pictures are very similar to those already given for operating by the positive process; frequent reference will therefore necessarily be made to portions of that process, as described in the preceding pages, and only such parts will be given here, as do not correspond with the foregoing.
It is thought advisable to omit in this chapter every reference that does not have a desired tendency to aid the operator in the plain straightforward order of manipulation. The negative process is fast becoming popular and needs the attention of all who desire to keep pace with the experiments in the art. Since the first edition of this work it has been my pleasure to see many fine photographic specimens produced by the following process, and noone need fail, if he will carefully adhere to the details given.
There perhaps may be circumstances making it advisable for some to have but one nitrate of silver solution for both positive and negative collodion pictures: for such, a process will be given in the following pages, which has recently appeared inHumphrey's Journal, and is called, after its author, the "Helio Process," this is well adapted for most purposes.
Soluble Cotton.
The method for preparing this has been given in page 41. It is prepared in the same manner for both positives and negatives.
Plain Collodion.
The preparation of plain collodion employed is the same as that described atpage 53.
Developing Solution for Negatives.
A little alcohol may be added to make it flow more evenly over the plate—say 1 oz.
This solution can be kept in a pint bottle, and should have a funnel devoted solely to the purpose of filtering it. One of the most convenient dishes for receiving this solution, when poured over the plate, is a bowl with a lip to it, as it can be readily poured back into the funnel.
The mode of employing this developer is the same as that for positives, described atpage 133. It may be used an indefinite number of times, but should be kept clean; it soon assumes a red color.
Re-developing Solution.
This solution is for the purpose of giving increased intensity to the negative, but as its use in the hands of beginners is attended with some difficulty, I would not recommend the operator to try it until he has had considerable experience in the developing process, or he will undoubtedly spoil his proofs. Its use requires promptness of action and quick observation.
The following is the formula for its preparation:
Put this into a bottle, and when the crystals are dissolved, it is ready for use. It should be kept filtered, and can be used only once. Now in another bottle put
Remarks.—The impression is to be well washed after the developing solution has been poured off, and then there-developing solution(that portion containing the protosulphate of iron) can be poured on—the plate being held perfectly level: the surface is completely covered; the water containing the nitrate of silver should then be pouredrapidlyon, to mix with the iron, when the surface of the impression will instantly commence to blacken; and if theaction be allowed to continue for a lengthened period, say one minute, the impression will be ruined.
It is a matter worthy of notice, that there is no perceptible action when the iron solution is poured over the glass; but the action is very energetic the instant the nitrate of silver solution comes in contact with the iron salt and the silver.
As soon as any change can be observed, after the re-developer has been poured over the plate, it should bequicklyand copiously washed off with clean water, and then it is ready for the fixing process.
I would dissuade novices in the art from practising with there-developing solution, until they have first thoroughly mastered the entire process of taking negatives. The developing solution is the only one used by operators generally, and will, with proper care, produce satisfactory results.
Fixing the Image.
Remarks.—This is nearly a saturated solution. The glass can be put in a dish and the solution poured over, or held in the hand, in the same way as the plate in the daguerreotype process. It can readily be seen when a sufficient action has been attained, as the unaltered bromo-iodide of silver will be dissolved, leaving only the reduced surface holding the image.
This action should not be continued too long, as it affects the intensity of the picture, injuring it for printing.
The glass should be well washed by pouring over it clean water, and then it can be stood away to dry, in anearlyperpendicular position, on clean blotting paper, or otherwise, as is most convenient; when thoroughly dry, it is ready for the finishing.
Finishing the Image.
This is done with the same material, and in the same manner, as that given for positives—page 134.
Remarks.—The glass negatives, when not wanted for use, should be carefully put aside in a box, and kept free from dust and dampness: by so doing, it is believed that they will remain good for any length of time.
Nitrate of Silver Bath.
This solution differs only from the positive bath, by omitting thenitric acid: in all other respects it is precisely the same, and is prepared by the same formula, as given atpage 64.
This is called theneutral bath, and is best adapted to the negative process. The nitrate of silver employed in its preparation should be perfectly free from excess of nitric acid, otherwise the whole solution will be slightly acid.
If it should not be convenient to obtain nitrate of silver without this objection, the acid may be neutralized by putting into the solution a small quantity of common washing soda— say 1 grain to each 100 grains of nitrate of silver—previously dissolved in about half an ounce of water. This may be put in at the same time that the iodide of potassium is, and it would save one filtration.
In twenty samples of nitrate of silver that I have triedthe above quantity of soda has been found sufficient; if, however, thewhiteprecipitate first formed is re-dissolved on shaking the mixture, free nitric acid is present, and more of the soda may be added.
This bath will improve by age, and be less liable to fog after having been in constant use for one or two weeks.
Operators who have the means, and design following the art professionally, will find it to their advantage to make from two to three times the quantity of solution they require for immediate use: by this means they will be enabled to replenish their stock, which may be used up or otherwise lost.
PRACTICAL DETAILS
OF THE
PRINTING PROCESS.
PRINTING PROCESS—SALTING PAPER—SILVERING PAPER—PRINTING THE POSITIVE—FIXING AND COLORING BATH—MOUNTING THE POSITIVE.
The Printing Process.
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 toHumphrey'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 tosaturatethe 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 anounce 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 theentire surfaceof 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:
Fig. 36.
Fig. 36.
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 onpage 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 placeddirectly 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.Hardwichin hisPhotographic 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 ofsodaimmediatelyon its formation, and so rendered more permanent by conversion into a double salt of soda and gold.
"Thetime of colorationdepends 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."—Thecoloringof 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 aphotograph, butan oilorwatercolor 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 thebestandmost durablepaste yet prepared for the purpose.