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
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THE knowledge of an imperfection or an error is half the correction. We must, therefore, first know what the failures in collodion negatives and positives are. Their enumeration is as follows
Fogginess; Spots and Apertures; Ridges and Undulating Lines; Streaks and Stains; Feebleness of the Image, or Deficiency of Contrast; Harshness or Excess of Contrast; Imperfect Definition; Solarization; Tender and Rotten Films.
Fogginess.--This is a mist or veil-like appearance that covers the whole negative; it gives it a foggy or clouded appearance. This imperfection may be the result of many and various causes, as for instance: Diffused light in the camera through holes or chinks; reflections from white or unblackened surfaces in the camera; diffused light through apertures or chinks in the door behind the plate in the plate-holder; direct rays of the sun through the objective or lens; an alkaline, neutral, impoverished or contaminated state of the nitrate of silver bath; a similar condition of the collodion certain iodizers in the collodion and at certain stages of ripening; diffused light in the dark-room; too intense artificial light in the dark-room; too intense a development; fumes of ammonia, of turpentine, of tobacco, of hydrosulphuric acid, and probably almost of any other volatile chemical substance in the developing-room; imperfect cleanness of a glass plate that has been used before; the use of gutta-percha baths and dippers.
Diffused light in the camera, either in front of the plate or behind it; Reflections from white or unblackened surfaces in the camera.--This is a certain cause of fogging, and can easily be remedied. Examine the camera carefully for all chinks and holes. Some photographers are very care less; they screw on the flanges of various-sized tubes on the end of the camera,, and neglect filling the apertures left by the screws when withdrawn. Chinks occur invariably in cameras made of green wood; and the bellows part, by frequent adjustment, sometimes cracks. The plate-holder has also its imperfections; the slide sometimes allows the entrance of light; the apertures at the bottom, for the passage of accumulating nitrate of silver, are frequently left open and not filled with sponge, so that light penetrates in this way. The door behind may close inaccurately; and the plate-holder may slide irregularly and not fill the groove calculated to receive it. All these are errors or defects of workmanship, which must and can be avoided or remedied. Look, therefore, to your camera first in the search of chinks, cracks, and apertures; secondly, if the inside surfaces of the camera are not of a dead black, cover them with unglazed black woolen or cotton cloth, or wash them over with a thick solution of ink or lampblack.
Direct rays of the sun through the axis of the lens. Avoid this evil; like many other troubles, to know it, is its total remedy.
An alkaline, neutral, impoverished or contaminated state of the nitrate of silver bath.--Immerse a piece of reddened litmus paper in the bath, and see whether it changes color, after a while, to a blue--if so, the bath is alkaline.
First remedy.--Make a mixture of six drops of acetic acid in a drachm of water, if you are taking negatives, and of the same quantity of nitric acid and water, if you are taking positives; add ten drops at a time of either solution until the fogging disappears. Sometimes even more acid may be required.
Second remedy.--Instead of adding acid to the bath, add an old collodion or tincture of iodine to your collodion in present use; this frequently is the safest plan of action.
If the bath is impoverished, it will at the same time be contaminated. The remedy is to boil it some time in a glass flask in order to get rid of the ether, alcohol, and the volatile substances produced by decomposition, as also to coagulate organic matter; then allow the bath to cool, and filter. To the filtrate add more nitrate of silver if required. Placing an old bath in the sun for several days is also of great assistance, but it is far from being equal to boiling or distilling.
Certain iodizers in the collodion and at certain stages of ripening.--Iodide of cadmium alone frequently produces fogginess; almost any new and limpid collodion has the same effect. Add iodide of ammonium in the first case, and an old collodion or tincture of iodine in the second case; the sensitiveness will be thereby probably diminished, whilst the condition to fog will be removed.
Diffused light in the dark--room, or too intense an artificial light.--Place the artificial light behind a piece of ground glass, and do not bring it near the negative until the latter is thoroughly fixed. Diffused light must be locked out of the room.
Too intense a developer.--In summer less of the developer, whether of iron or pyrogallic acid, or more of the acid is required than in winter, otherwise fogging will be the consequence--the property of acid is to restrain the action of the developer; use your judgment, therefore, and do not always keep to the same amount of protosulphate of iron, or pyrogallic acid to the ounce of water in all seasons; nor restrict yourself unconditionally to the same amount of acid in the developer.
Fumes of ammonia, etc.--Keep your dark-room solely for its legitimate purposes. Keep it rigidly clean; perform no chemical experiments in it; abjure smoking in this sanctum; do not sensitize your papers or fuminate with ammonia in this room; make no manner of fumes therein.
Imperfect cleanness of the plate, etc.--Wash the old plates with a solution of salts of tartar and water; if this does not remove the adhering dirt, wash it with dilute nitric acid, and afterward with salts of tartar, and finally clean and polish the plate with rotten-stone and alcohol. Some old plates that have lain long in water in which the old developing solutions have been thrown I have never succeeded in cleaning so as to prevent fogging; they are contaminated to the backbone.
The use of gutta-percha baths, etc.--Instead of these, use glass, porcelain or photographic ware baths--the latter are very highly recommended; I prefer glass to every other material.
Opaque and transparent specks are the most troublesome annoyances in the collodion negative process, and occur to every photographer more or less. These can be attributed to various causes, but seldom for the time being to the right cause; that is, we know in general what will cause them, but seldom what did cause them.
The opaque spots may be caused in the first place by dust on the surface of the glass before the collodion is poured on. The remedy is simple: brush off the dust with a broad, flat camel's hair pencil just before the collodion is applied.
Secondly.--Opaque spots may be caused by dust on the surface of the collodion; this dust may be deposited either from the bath itself, previous to immersion in the bath, or in the camera during exposure. That which is deposited either before or after immersion, are the organic substances in a state of very minute division floating about in the atmosphere or set in motion within the camera by the agitation produced with the plate-holder. This is perhaps the most fruitful source of trouble, which is of two kinds, opaque and transparent spots. The particles of dust attach themselves to the collodion with different degrees of tenacity; where the tenacity is small, the dust is washed off; in the different manipulations of developing and fixing, and the consequence is the production of transparent specks; on the contrary, where the tenacity is great, opaque spots are the result; for the particles remain imbedded after the final washing. If the dust be deposited from the bath itself, it may arise either from organic materials, in the atmosphere or from an excess of iodide of silver in the bath, in the form of the violet-colored deposit found at the bottom or on the walls of the bath. The remedy is, in the first case, to keep your room-floors moist, and your camera perfectly free from this enemy by dusting and sponging. In the second place, the insoluble deposit in the bath is separated by filtration; the bath, too, is thoroughly cleaned by a sponge tied to the end of a rod, which can be made to enter into the angular spaces in which the dust is deposited.
Thirdly.--Another source of this trouble with opaque spots is to be found in the collodion, which contains sometimes undissolved pyroxyline in the form both of dust and fibres, or in fine organic dust from impure sources of manipulation. To remedy the evil, allow the collodion to settle thoroughly and use only the clear supernatant part.
These are of much more frequent occurrence than opaque spots. They may arise, in the first place, from undissolved particles of the iodides in the ether and alcohol of the collodion; this is particularly the case with iodide of potassium in anhydrous alcohol; these afterward become dissolved in the subsequent operations. The remedy is a drop or two of water, or of diluted alcohol, or of bromide of ammonium.
As remarked in reference to opaque spots, particles of dust in the camera or of the insoluble iodide of silver in the bath, adhering to the surface of the collodion, produce specks, both opaque and transparent. The transparent ones result from the fact that, during exposure, and the dust particles being opaque, they prevent the rays of light from acting actinically on the collodion film beneath, and then, being washed off in the subsequent manipulations of development, fixing, intensifying, and washing, they leave the collodion in those parts to the mercy of the fixing solutions, which render them quite transparent. The remedy is to keep the camera and the room free from dust, and the bath from insoluble particles of the iodide of silver or organic materials. If the bath is the cause, the trouble may be avoided by keeping the plate in motion during sensitization.
Another cause of transparent spots, and probably a very frequent one, is to be attributed to a crystalline deposit of iodo-nitrate of silver, which, as the bath becomes weaker, is precipitated in a crystalline form on the surface of the collodion film. This form of deposit occurs with an old bath. Its remedy is to precipitate it out of the bath by adding water, and then by filtration. Then for every ounce of water thus added pour in after filtration the same amount of a nitrate of silver solution to take its place.
When the bath is the cause of transparent spots, a small quantity of a solution of chloride of sodium (common salt) thrown in is found to be of great benefit. Chloride of silver and nitrate of soda are formed by double decomposition; the insoluble chloride probably carries down with it the dust or particles which are the cause of the trouble, or the nitrate of soda dissolves them. I am not able to say what is the true explanation. After filtration the bath is raised to the proper strength, when it will be found to be free from the evil.
These are caused by the too great consistency of the collodion, and are found in the direction of the current of the collodion. The remedy is to add sufficient ether to cause the collodion to flow smoothly, easily, and uniformly over the plate. The mottled appearance sometimes apparent on a collodion film, as if covered with flocks of wool, is owing also to the thickness of the collodion, and the evil is remedied in the same manner as the ridges.
Streaks may arise from an irregularity in the immersion of the plate in the silver bath, or in withdrawing it; the plate has to be immersed or withdrawn without any stopping. Streaks and stains are produced, too, by the film of dust swimming on the surface of the vertical bath, which is carried down on the collodion when the plate is immersed.
They arise, secondly, from the irregular flowing of the developing solution; the remedy is to use the gutta-percha developing dish already recommended for such purposes. Another remedy may be a proper quantity of alcohol added to the developer, if there happen to be a sort of greasiness or repulsion in the collodion film to the developing solution as it flows along.
The part upon which the developer first comes in contact with the collodion film almost invariably exhibits a streak around a denuded part, as if the developer had swept off the latent image in that part. The remedy is the developing dish, by which the developer acts with little or no momentum greater at one part than at another.
A sort of fortification system of stains and streaks arises from the want of cleanness of the corners of the plate-shield, from an inferior quality of collodion, from the unequal dryness of the film before immersion in the silver bath, as well as from a too great and irregular dryness of the film after exposure and before development. The remedies are self-apparent; avoid the causes.
Stains of a blue color arise from imperfect washing between developing and fixing.
A new collodion will very frequently be one cause of this trouble--the materials are not yet ripe. As a remedy, add old collodion, or wait for a few days, until the collodion is sufficiently decomposed.
Over-exposure is another and very frequent cause of a feeble contrast in the picture. All the parts are developed simultaneously, and too much deposit of reduced silver is the result all over the picture. A shorter exposure is the remedy.
Too intense a developer, or a developer continued too long, fogs the picture and weakens the contrast.
Imperfect lighting, is a third cause, in which the light is either small in quantity, or diminished in intensity bar reason of peculiarities in the atmosphere.
Under-exposure, a too acid bath, a too acid developer, underdevelopment, an old and insensitive collodion: all these will produce pictures of mere black and white; the intermediate tones are totally wanting. The remedy is apparent; use it as the case may be.
This may be caused by the want of coincidence in the chemical and luminous focus. See that the surface of the ground glass and that of the inserted plate have exactly the same distance from the back lens, and correct this evil according to rules already laid down.
The want of sharpness may arise from careless focussing, from the mobility of the sitter during exposure, from a change of position in the camera when inserting the sensitized plate, or, in fine, from a bad lens. The remedy in everyone of these cases is obvious, excepting perhaps in the last; for the photographer may not always be in a condition to get a better lens. The only and most advisable remedy in this case is to close his gallery and feign sickness, until the return of the Express from the city, rather than lose his reputation or gain a bad one. In many cases a microscope is employed in very refined focussing, especially in copying.
This trouble does not occur very frequently; it is made manifest by the redness which the high-lights are wont to assume during development, when the exposure has been either too long or the light too brilliant, as in the copying process by the direct rays of the sun. This evil can be remedied by avoiding the causes, or by the use of a bromo-iodized collodion, or of citric acid in the developer.
These occur generally in collodion of a certain make, owing to the peculiar nature of the pyroxyline, or the relative quantity of alcohol and ether. The defect may arise, however, by immersing the plate too quickly into the silver bath before the film has set; also by immersing the plate when the film is too dry, in which case it cracks and splits up in the development.
There is no remedy for a rotten film; but a tender or structureless film can be retained on the glass by first filing the edges as recommended, and then by careful manipulations in the various operations of developing, fixing, and washing.
These are to be attributed to defects in the paper; to Imperfect albumenizing and salting; to defective sensitizing; to defects in the printing or in the negative; to imperfect washing previous to toning; to defective toning; to defective fixing; to stains of various kinds; meatiness on the print.
A defective piece of paper must always be rejected at once. By regarding the paper by transmitted light, very frequently imperfections in the substance of the material can be descried, which otherwise would escape observation. Particles of inorganic matter, such as lime, the oxide of iron, etc., may be found in the substance, which in the various stages of the printing operation become manifest by decomposition. In choosing paper, where you can make the selection, examine each sheet separately for mechanical defects both of structure and of contamination, and reject whatever is in any way defective.
The albumenizing and salting require careful and neat management. If the albumen is not very thoroughly broken up, it will assuredly produce irregularities in the albumenizing. The salting materials must be mixed up at the same time with the albumen, but after solution in a small quantity of water; otherwise particles of the salt will remain undissolved and give a spotted appearance in the printing. Use the albumen while fresh. See that the surface is not composed of bubbles; where these exist you will have a marbled or oölitic appearance on your print. If the paper exhibits such minute bubbles when removed from the salting solution, break these bubbles all up with a clean feather or soft sponge, and goat the paper again until the film is uniform. The amount of salting ought to bear a relation of equivalents with the silver solution used subsequently.
Filter the silver solution before use, or at least remove all particles of dust or oxide from its surface, otherwise your prints will be spotted and frequently covered with fortifications. A marbled appearance is caused by a weak silver solution, or too short a time of floating. It may arise from defects in the albumenizing, as just referred to. In quick floating the solution must be very strong. In some cases the solution seems to be rejected from the surface of the albumen; rub over the solution with a tuft of cotton; float again, and the trouble will be overcome.
A weak negative will inevitably produce a weak print. Weak prints, too, are the result of too dilute a silver solution. Bronzing arises frequently from a want of true relation between the lights and shades in the negative. An intensified ambrotype used as a negative will produce a bronzed picture. Thus under-exposure and over-development are the causes of bronzing.
A harsh print proceeds also from under-exposure and over- development in the negative; there is a want of middle-tone--the picture is all black and white.
Many prints are spoiled in the act of printing by extreme carelessness. Watch the operation; the two guides of success are: Print as long as the high-lights are perfectly white, and bronzing has not yet commenced. The impression of a perspiring finger on the sensitive film, as well as many other similar organic contaminations, also give rise to bronzing.
The print, when removed from the printing-frame, contains nitrate of silver and nitrate of the alkalies used in the salting solutions, albuminate of silver, chloride of silver; the latter salt has been partly acted upon by fight so as to form the picture, and another part has not been changed. The nitrates must all be removed by careful washing in several waters before the toning is commenced, otherwise the toning will be slow and imperfect.
The operation of washing must take place soon after printing and immediately before towing, in order to secure a good and quick tone.
This imperfection may arise from contaminations introduced into the toning solution by imperfectly washed prints; the gold solution becomes thereby decomposed and incapable of toning the printed film. The defect may arise from impure chloride of gold; from an acid condition of the toning solution; from bad paper; from the lowness of the temperature; from an excess of elevation of temperature. The imperfections of toning are
A red tone after fixing; this is owing to an insufficiency of toning.
A blue tone after fixing; this is owing to an excess of toning; or to an acid toning solution.
A yellow tone in the whites after fixing; this may be owing to imperfect washing, imperfect toning, imperfect fixing, dirty fingers, introduction of hyposulphite of soda into the toning solution, or upon the prints. The defect in question may arise also from the decomposition of the gold in patches, for want of uniform mixture before the prints are introduced.
A dark mottled appearance in the body of the paper indicates imperfect fixing combined with the action of the light on the unaltered chloride during fixing. An exhausted hyposulphite bath may also give rise to this defect. A bath containing hydrosulphuric acid, or a free acid, which will produce the former, gives rise to this dark-gray mottled defect.
A yellow tone in the whites arises very frequently from sulphurized hyposulphite stains of various kinds.
These are owing to irregular and careless manipulations. The introduction of the fingers into the various baths, and indiscriminately from one bath into another, is the cause of a number of stains on the prints, as well as of abnormal action of the baths themselves.
Make rules for yourself, such as the following, and observe them minutely
Some authors speak of this defect in albumen prints. It is said to proceed from paper that has been long albumenized, or from the paper itself. The remedy is to immerse the prints in a solution of two ounces of water and eighteen grains of acetate of soda, and to keep them in this liquid for about ten minutes.
Prints frequently appear as if covered with snow, but the surface is quite smooth and the whites clear; this defect is attributable to the negative, which has been strengthened by pyrogallic acid containing too much nitrate of silver. The surface of the negative becomes thereby covered with a pulverulent deposit. There is no remedy for such a negative; there is a remedy, however, to such a mode of intensifying. In the first place, the negative must contain the middle tones before you begin to intensify; secondly, intensify slowly, which is effected by adding only three or four drops of silver at a time to the pyrogallic acid, and shaking well before use.
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