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A Tournette Chardon's method of coating

PREPARER'S NOTE

Please remember that this book was published over a century ago, long before today's chemical safety standards. Please get expert advice before attempting to perform any of the procedures described in this book.

INTRODUCTION.

The photographic processes with the salts of iron are all derived from the researches of Sir John Herschel. The investigations of that great philosopher are so valuable, so full of instructions that we are led to reprint them, together with those of Mr. C. J. Burnett, on the salts of uranium, etc., as an Introduction. It will be seen that the process by which blue prints are to-day obtained is exactly that Sir John Herschel devised in 1840.

"Paper simply washed with a solution of this salt is highly sensitive to the action of the light. Prussian blue is deposited . After half an hour or an hour's exposure to sunshine, a very beautiful negative photograph is the result, to fix which, all that is necessary is to soak it in water in which a little sulphate of soda is dissolved. While dry the impression is of a dove color or lavender blue, which has a curious and striking effect on the greenish yellow ground of the paper produced by the saline solution. After washing the ground color disappears and the photograph becomes bright blue on a white ground. If too long exposed, it gets 'over-sunned,' and the tint has a brownish or yellowish tendency, which, however, is removed in fixing; but no increase of intensity beyond a certain point is obtained by the continuance of exposure."

"If paper be washed with a mixture of the solutions of ammonio-citrate of iron and ferrosesquicyanate of potash, so as to contain the two salts in about equal proportions, and being then impressed with a picture, be thrown into water and dried, a negative blue picture will be produced. This picture I have found to be susceptible of a very curious transformation. To effect this it must be washed with a solution of protonitrate of mercury, which in a little time entirely discharges it. The nitrate being thoroughly washed out and the picture dried, a smooth iron is passed over it, somewhat hotter than is used for ironing linen, but not sufficiently so to scorch or injure the paper. The obliterated picture immediately reappears, not blue, but brown. If kept for some weeks in this state between the leaves of a portfolio, in complete darkness, it fades, and at length almost disappears. But what is very singular, a fresh application of heat revives and restores it to its full intensity."

Sir John Herschel then proceeds to show that whatever be the state of the iron in the double salts in question, its reduction by blue light to the state of protoxide is indicated by many other agents. "Thus, for example," says Robert Hunt, "if a slip of paper prepared with the ammonio-citrate of iron be exposed partially to sunshine, and then washed with the bichromate of potash, the bichromate is deoxidized and precipitated upon the sunned portion, just as it would be if directly exposed to the sun's rays."

"I have proved this fact with a great number of preparations of cobalt, nickel, bismuth, platinum and other salts which have been thought hitherto to be insensitive to the solar agency; but if they are partially sunned and then washed with nitrate of silver and put aside in the dark, the metallic silver is slowly reduced upon the sunned portion. In many instances days were required to produce the visible picture; and in one case paper being washed in the dark with neutral chloride of platinum was sunned and then washed in the dark with nitrate of silver; it was some weeks before the image made its appearance, but it was eventually perfectly developed, and, when quite so, remained permanently impressed upon the paper."

The following process, discovered at the same time as the cyanotype, and termed chrysotype, is thus described by Sir John Herschel:

"If paper prepared as above recommended for the chrysotype, either with the ammonio-citrate or ammonio-tartrate of iron, and impressed, as in that process, with a latent picture, be washed with nitrate of silver instead of a solution of gold, a very sharp and beautiful picture is developed of great intensity. Its disclosure is not instantaneous; a few moments elapse without apparent effect; the dark shades are then first touched in, and by degrees the details appear, but much more slowly than in the case of gold. In two or three minutes, however, the maximum of distinctness will not fail to be obtained. The picture may be fixed by the hyposulphite of soda, which alone, I believe, can be fully depended on for fixing argentic photographs."

"The best process for fixing the photographs prepared with gold is as follows: As soon as the picture is satisfactorily brought out by the auriferous liquid, it is to be rinsed in spring water, which must be three times renewed, letting it remain in the third water five or ten minutes. It is then to be blotted off and dried, after which it is to be washed on both sides with a somewhat weak solution of hydriodate of potash. If there be any free chloride of gold present in the pores of the paper it will be discolored, the lights passing to a ruddy brown; but they speedily whiten again spontaneously, or at all events on throwing it into fresh water, in which, being again rinsed and dried, it is now perfectly fixed."

"In the first process, the paper being charged with the uranic salt and exposed to the solar influence under the negative to be copied, is washed with a solution of the ferridcyanide or red prussiate of potash. The 'Harvest Scene' in the exhibition, being from an albumen negative lent me by Mr. Ross, the well-known Edinburgh photographer, is an example, the salt of the sesquioxide of uranium being in this case the hydrofluate, and the time of exposure from the strength of the albumen negative fully an hour of good sunshine. I have used for the solution of the uranic oxide for this process a variety of acids with very similar results; the sensitiveness of the prepared paper to light varying much, however. For instance, a collodion negative with the hydrofluate paper producing a very good print in half an hour of unsteady sun, while with a paper prepared with the tartaric acid solution of the oxide, it gave an equally good impression in less than five minutes of the same intermitting sunshine, indicating thus a difference of sensitiveness of six to one in favor of the tartrate."

"The rationale of this process is the reduction of the sesqui-oxide of uranium, U2O3, on those parts of the paper exposed to the solar influence, to a lower state of oxidation, the photo-oxide UO, the salts of which have the property of forming with soluble alkaline ferridcyanides a rich chocolate-brown precipitate, while the salts of the sesquioxide are destitute of this reaction. Hence the brown deposit on the parts of the picture on which the sun has been allowed to act when the developing solution is applied, and the absence of any such appearance on those parts which have been protected from its influence."

"As to the manipulatory details of this process, the paper is floated on the solution in a dark room and hung up to dry, and then preserved from light in a portfolio. If carefully secluded from light it appears to keep well. After exposure for the proper time under this negative, there is in some cases scarcely any visible impression; while in other cases, particularly when using the tartaric solution, I have found the impression very distinguishable, of a brownish or blackish shade, although still quite faint. The development is best conducted by floating it, anything like rubbing the picture being very objectionable."

"I have since had the opportunity of trying the nitro-prusside of sodium, which, by itself, gives a blue and white picture, in color like that obtained from the red prussiate of potash."

THE DESIGNS.

HOW TO MAKE A NEGATIVE DRAWING

The drawing paper for designs to be reproduced by the cyantotype and the other processes described in this book should be of a fine texture, free from opacities and very white; and, as the design must serve as a clich? it is a sine qua non that it be drawn with a very black ink and with well-fed lines, especially those which are very fine. To obtain a complete opacity, and, at the same time, to keep the ink quite fluid, which gives great facility to the designer, one adds some gamboge to the India ink. The ink of Bourgeois, which is compounded with yellow and can be diluted as easily as India ink, is excellent, so is also the American ink of Higgins.

As much as possible it is desirable to replace the colored lines indicating the constructions, the axis, projections, etc., by differently punctuated lines made with India ink. However, if the use of colors be obligatory on the original design, one should trace the red lines with very thick vermilion or sienna, the yellow lines with gamboge, and the blue and green lines with a thick mixture of Prussian blue and chrome yellow in different proportions.

One must abstain from applying washes of any tints on the original. If necessary they should be brushed over when the reproductions are made; moreover they can be often replaced by cross-lines more or less open, and the shadowing represented by thicker but not closer lines.

Tracing paper is recommended instead of linen, which latter, on account of its thickness and granulation, gives less satisfactory results in regard to the transparency of the ground and the continuity of the lines.

To reproduce a design on ordinary paper--not too thick--or an engraving, etc., the paper is rendered transparent by rubbing over on the back of the original a solution of 3 parts in volume of castor oil in 10 parts of alcohol, by means of a small sponge. When the paper is quite transparent, the oil in excess is removed by pressure between sheets of blotting paper, and the paper dried before the fire or spontaneously. The design so treated is not in the least injured, for it assumes its primitive condition by dissolving the oil from the paper by immersion into strong alcohol, which it is necessary to renew once or twice, then rinsing in alcoholized water if the drawing be in India ink, or simply in water in the case of an engraving, and finally drying between sheets of blotting paper.

Instead of an alcoholic solution of castor oil, vaseline can be employed. The paper is more transparent.

The method by which are made negative drawings, that is, those which can be used as negative clich?s to reproduce the design in black lines on a white ground, is thus described by Mr. Cheysson, wlio originated it, in a manual published by the Department of Public Works of France, from which we have borrowed most of the above instructions for the drawing of designs suitable for the photo-reproduction processes:

"One can avoid the necessity of making a negative from the original drawing by transforming the drawing itself into a negative."

"To that effect it suffices to draw with lithographic ink, then to cover the paper with aniline brown, and, after drying, to wash it with turpentine oil which dissolves the lithographic ink without altering the aniline. The lines appear then white on a brown ground impervious to light . The design is thus transformed into a negative, and can yield positive impressions with paper sensitized with silver salts, the ferriprussiate or the bichromate of potash. The lithographic ink should be very black and the lines well fed."

"When the drawing is finished it is placed on a board lined with sheets of blotting paper, then one spreads all over it the aniline brown with a brush, and, lastly, after drying, the paper is carefully rubbed with a bung of cotton or a rag imbued with turpentine until the lines of the design are dissolved."

In our practice we have often taken a negative clich? from drawings made in the ordinary manner, without the aid of the camera obscura , by simply printing a proof by contact on plain or albumenized silvered paper, and fixing, without toning, in a new solution of sodium thiosulphate, then washing as usual. The proofs thus obtained from designs drawn with an opaque ink, which allows a long insulation and, therefore, yields an intense reduction, are of a deep brick-red color, quite non-actinic, and give very good positives by the Artigues process.

N.B.--Paper in drying never assumes its original shape; it is, therefore, necessary to make the figures on the reproductions from plans when they are not on the originals.

CHOICE OF PAPER. SIZING.

In all the photographic processes by precipitation of metallic oxides the quality of the paper has a great influence on the results. When the paper is not well sized and not well calendered, the sensitizing solution is absorbed, instead of simply impregnating the surface of the paper, and not only the image is sunk in and its sharpness impaired, but good whites can never be obtained, especially if the image should be toned, owing to the impossibility of eliminating the metallic salts not acted on, that is, not reduced by the action of light which the fibers of the paper mechanically retain.

The "endless" rolls of paper, 54: inches wide--or "blue print paper," as it is sometimes termed--of Blanchet fr?res et Kl?ber, of Rives, better known as "Rives' paper", that of Johannot, of Annonay , and the Steinbach paper are recommended.

For small prints from negatives in half tone the positive paper, 18x22 inches, of Rives or Saxe, should be preferred to the heavy kind. It is advisable to size it, so that the impressions be entirely formed on the surface of the paper. Moreover, an additional sizing is always advantageous, whatever be the photographic process employed, to prevent the imbibition of the sensitizing compound and to obtain more brilliant and vigorous images, for the iron, chromium, uranium and other metallic soluble salts require the presence of an organic matter to be reduced by the agency of light; and as a consequence, the greater, within certain limits, of course, the amount of organic matters, and the more thoroughly they are mixed with the salts, the more sensitive the preparation and the better the results.

Arrowroot is the best sizing for our purposes. Gelatine may be employed, albumen also, but the coating should be insolubized when applied on the paper and dry.

Another, but not quite so effective a manner of sizing although sufficient for the cyanotype, is the following, employed by Mr. Pizzighelli for the paper used in the platinotypic process:

Ten parts of arrowroot are powdered in a mortar with a little water and then mixed by small quantities to 800 parts of boiling water. After a few minutes 200 parts of alcohol are added and the mixture filtered. The paper is immersed for two or three minutes in the warm solution and hung up to dry.

THE CYANOTYPE OR BLUE PROCESS.

The process is indeed exceedingly simple. A sheet of paper, impregnated or sensitized, as it is termed, with a solution of ferric citrate and ferricyanate is impressed under a clich?, then immersed in pure water, whereby the image is developed and at the same time fixed. It is on account of the great advantages offered by its simplicity that this process is generally preferred by civil engineers and architects for the reproduction of their plans.

The sensitizing solution is prepared in mixing by equal volumes the two solutions following:

A. Iron, ammonio 20 parts citrate Water 100 parts B. Potassium 15 parts ferricyanate Water 100 parts

Although the mixture keeps pretty well for a certain period in the dark, it is best to prepare only the quantity wanted for actual use.

The paper is preferably sensitized in operating as follows:

The rationale of this manner of sensitizing is to impregnate only the very surface of the paper with the ferric salts, and thereby to obtain an intense blue with very good whites, which latter it would be impossible of obtaining should the sensitizing solution be allowed to reach in the fibers of the paper, for, in this condition, it is impossible, owing to the exigencies of the process, to wash out thoroughly the iron salts to prevent the chemical changes which cause the whites to be tinted blue. It is for this reason that better results are also obtained with well sized papers.

The sensitizing should be done by a very diffused daylight, and the drying, of course, in a dark room. When sensitized the paper is yellowish green. It should be well dried for keeping, and rolled or wrapped in orange or brown paper and preserved from the action of dampness and of the air. It does not keep well, however, no more than two or three months, perhaps, in good condition; but the sooner it is employed the finer the proofs, the better the whites and more rapidly is the paper impressed.

There is in the market a paper which keeps for a long time. It is prepared by adding a small quantity of gum arabic or of dextrine to the sensitizing solution. Good for the reproduction of line work, it does not give very satisfactory results for pictures in half tones.

The following compound gives a paper much more sensitive, but not keeping so long, than that prepared according to the formula previously given:

Tartaric acid 25 parts Ferric chloride, solution 80 parts at 45 deg. Baum? Water 100 parts

When the acid is dissolved, add gradually concentrated aqueous ammonia, just enough to neutralize the solution--170 volumes, about. The chemical change consists in the formation of ferric tartrate. Let cool the solution, then, after adding the following, keep it in the dark:

Potassium ferricyanate 21 1/2 parts Water 100 parts

Another and very sensitive preparation is the following:

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