Chapter 2

“When the picture has fully come out, which is generally from three to ten minutes at the very most, it is removed from the developing bath, placed in cold water and washed very gently for a few minutes, the water being frequently changed till it ceases to acquire a yellow tinge from the dissolved red prussiate. The picture is then drained from the water, pressed between folds of blotting paper, dried (I dry in the dark), and the process is complete. * * * I may state, as one recommendation of this process to ladies and other lovers of clean hands, that any brown stains left by it on the fingers or elsewhere are at once removable by a little weak ammonia or soap and water. * * * I would particularly suggest, as deserving of notice, the development of the salts of sesquioxide of uranium, and still more iron, by the metals and metallic-cyanic alkaline salts, as also by the mellonides and nitro-prussides, and the latter also by itself and as developed by many metallic salts.”

“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.”

“When mixed with a solution of ammonio-nitrate of copper, previous to its application to the paper, the color obtained is pale purplish pink or peach-blossom color. By mixing it in the same way with ammonio-oxalate of sesquioxide of iron, we get a dull green picture, changeable through intermediate stages into brown by alkaline carbonates, and that into a _dirty_ black by gallic acid. It may be well to know that the blue of the picture given by the red prussiate in the process of Sir John Herschel may be considerably modified or entirely changed to another color, in many ways, without interfering with the purity of the white ground, by steeping the picture, after the undecomposed red prussiate has been washed out, in solution of salts of various metals, copper, uranium or cobalt, for instance, and that the colors so produced may be modified as desired, according to the stage at which the action is stopped.”

“There remains but one class of uranic photographs to be described, namely, that obtained when we develop with a salt of silver or gold (or platinum?). This class may be made to print much more rapidly than our ordinary silver printing process, approaching sometimes more nearly to the calotype development in this respect. We get the _minutest details_ with great fidelity, and the picture is effectually fixed by a simple fresh hyposulphite solution, with a good color in many cases, or by ammonia, which will be considered an advantage by those who hold the hyposulphite an enemy to durability. Different shades of color are produced according to different solvent acids and different details. I have got a good black perfectly like that of an engraving, by the nitrate of uranic oxide, developed by ammonio-nitrate of silver (or plain nitrate) and fixed by plain hyposulphite without any coloring bath. * * * I have tried the hyposulphite of gold on some of the silver-developed prints prepared with the hydrofluate of the uranic oxide and fixed with ammonia, which had an exceedingly unpleasant raw-red color, a very agreeable gray was at once obtained. I have succeeded in getting very beautiful impressions by development of the uranic paper by chloride of gold alone.”

In another communication to the _Photographic Notes_, more interesting perhaps than the foregoing, Mr. Burnett says:

“The clearest and brightest of my results have been obtained by the action of gallic acid, tannin, or especially a _mixture of tannin and carbonate of ammonia_, potash or soda, on the blue pictures obtained by the solarization of paper prepared with ferridcyanide of potassium, ferrocyanide or ferridcyanide of ammonium. * * * I have also experimented with the bichromate and iron, with gallic, tannin and other developer; but I must confess to not having been, in this particular way, so successful as Mr. Sella appears to have been in the preservation of the whites, owing possibly to my not having taken the trouble to wash out sufficiently the iron before toning.”(1)

“I have experimented most extensively in many ways with the chromates and bichromates, and have succeeded in various ways in getting _very good_ results. A very capital process for many purposes is to float or steep your paper in a mixed solution of bichromate of potash and sulphate of copper. As for E. Hunt’s chromotype process,” (2) I have mixed gelatine, or occasionally grape sugar, or both, with the solution, but instead of developing it by a silver solution, as in the chromotype, wash out the salts unacted on by light, and develop by floating on a solution of ferrocyanide of potassium. The color of the red copper salt which now forms the picture may be modified or changed in many ways, viz., by soaking the picture, after the ferrocyanide of potassium has been washed out of the lights, in a solution of sulphate of iron (or the iron salt may, but not so advantageously, have been applied to the picture before the application of the ferrocyanide). Solutions of chloride of tin, gallic and tannic acids, alone or with alkalies or alkaline carbonates, may also be employed to modify or change the color. Instead of developing by ferrocyanide you may develop by the cobalt or chromo-cyanogen salts, or by an alkaline _mellonide_ arsenite, etc. Sulphureted hydrogen, or a sulphide, will give a _brown_, or _black_ tone, which may be protected against oxygen and dampness by a resinous varnish.

“Of all the simple pictures obtainable with bichromated papers, without complications or other tonings, those obtainable by the combination of a salt (say the sulphate) of _manganese_, with the bichromate in the paper preparation, are about the best; these pictures being, however, capable of being toned and modified in many different ways if desired. This may be accomplished by the use of toning baths of ferridcyanide or ferrocyanide, or other metal cyanogen salts, etc., or by either mixing the salts of other metals, as copper or iron, with the cyanic toning baths, or using them in the original solution, or by soaking the paper in them, as in Sella’s process, previously to the application of the metal cyanic, mellonic or other toning baths. Alkalies and alkaline carbonates may also be used to remove the chromic acid, and leave a subsalt, or the very stable oxide or carbonate of manganese, which may be peroxidized by the use of chloride of lime, peroxide of hydrogen, or ozone.”

“In all the processes with metallic salts, alone with bichromates, the use of sized or unsized paper along with gelatine, etc., has some advantages. I have got good results by such processes on albumen paper, the albumen tending to prevent mealiness in the print; also on paper soaked in gelatine before the application of the bichromic solution. * * * There is great interest connected with the action of all such papers, along with the tannin and vegetable coloring matters. I have long been of opinion that by the steeping of papers or textile fabrics, containing the salts not only of iron, as recommended by Mr. Sella, but of tin, copper, bismuth, lead, etc., in solutions of cochineal, red cabbage, beetroot, grass or the most ordinary foliage, etc., that the most useful results might be obtained; though for _certain_ permanence I am not sure but that some of the other processes which I have briefly run over with the cyanogen acid salts or metallic acid salts, as precipitators, may be more to be depended upon. The processes with _precipitated oxides_, such as the one with manganese and similar ones, with other metals which I have described, I also consider as deserving of more attention than almost any processes which have been stated, on the score of probable permanence; but perhaps the best process for black, or generally useful neutral tint, without silver, that has yet been offered to the public, I believe to be the process alluded to with the bichromate of potash and sulphate of copper, toned by an iron salt. * * * This process, the cuprotype (as also the uranotype and manganotype) is applicable perfectly to films of _albumen_ or gelatine on glass or porcelain, textile fabrics, parchment, paper, tiles and many other substances besides paper.”

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 cliché 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 (or burnt sienna) 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.(3)

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 clichés 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:(4)

“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 (that is, non-actinic). 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 cliché from drawings made in the ordinary manner, without the aid of the camera obscura (which would have been too expensive for drawings of a certain size), 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 fréres et Kléber, of Rives, better known as “Rives’ paper”, that of Johannot, of Annonay (France), and the Steinbach (Saxe) paper are recommended.

For small prints from negatives in half tone the positive paper, 18×22 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 (alcohol, ether, gum arabic, glucose, caseine, etc.) 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.

_Sizing with Arrowroot._—In a porcelain dish diffuse 4 parts of powdered arrowroot and one part of liquid glucose in 200 parts of distilled or rain water and dissolve by heat over an alcohol lamp, stirring all the while. Let the solution boil for an instant, and when the paste is homogeneous let it cool down and then remove the skin formed on its surface and strain it through a fine canvas. Now provide with three small sponges free from gritty matters and cleaned in water, and nail by the four corners, one over the other, felt size uppermost, as many sheets of paper as you wish to size on a board somewhat smaller than the paper. This done, with one of the sponges take a small quantity of the arrowroot and, brushing it length-way and cross-way, spread the paste into an even layer, then, by rubbing very lightly with the second sponge, efface the striae and smooth the coating as well as possible. The third sponge serves to remove the excess of paste when too much is at first spread on. From six to seven sheets of paper, 18×22, can be sized with the quantity of arrowroot paste above given.

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.

_Sizing, with Gelatine._—Dissolve at a temperature of about 140 deg. Fahr. (60 deg. C.) 10 parts of good gelatine in 800 parts of water, then add 200 parts of alcohol and 3 parts of alum dissolved in a little water. Filter and prepare the paper by immersion as above directed. The gelatinized paper when dry should be prepared a second time and dried by hanging it up in the opposite direction in order to obtain an even coating.

THE CYANOTYPE OR BLUE PROCESS.

_This process gives white impressions on a blue ground with diapositives or drawings on transparent or semi-transparent materials, and blue impressions on a white ground from negatives._ It is commonly known under the names of “blue print process,” “negative ferrotype process” and “ferro-prussiate 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 cliché,(5) 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 (red prussiate) 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.(6)

The paper is preferably sensitized in operating as follows:

Take hold of the paper by the two opposite corners and fold it into a loop, lay it on the iron solution, the center of the sheet first placed in contact with the liquid, and then gradually spread it by lowering the corners with a little pressure. No solution should run over on the back of the paper; it would be a cause of stain. This done, and without allowing the liquid to penetrate _in_ the paper, immediately take hold of the two corners near the body and withdraw the paper by dragging it over on a glass rod for this purpose fixed on the edge of the tray. Now pin up the paper to dry, which should be done rapidly, and sensitize a second time in proceeding in the same manner. If this second sensitizing be found objectionable, let float the paper for no more than ten seconds; of course this method of sensitizing is not applicable to prepare larger sheets of paper. In this case the paper is pinned by the four corners on a drawing board or any other support, lined with blotting paper and quickly brushed over with a sponge sparingly imbued with the sensitizing mixture, so as to wet the paper with a very small excess of liquid.

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 (in volume) at 45 deg. Baumé 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 21½ parts Water 100 parts

Another and very sensitive preparation is the following:

A. Iron perchloride, 40 parts cryst Oxalic acid 10 parts Water 100 parts B. Potassium 20 parts ferricyanate Water 100 parts Mix

_Printing._—The process we describe yields negative impressions, that is a positive image from a negative cliché, and a negative image from a positive cliché, exactly as the silver printing-out process ordinarily employed in photography. Consequently, for the production of non-reversed proofs from plans, etc., the original drawing should be placed _face downwards_ on the glass plate of the printing frame, and, upon the back, the sensitive paper is laid and pressed into perfect contact by means of a pad, felt or thick cloth.

The printing frame is that used by photographers. The lid is divided, according to the side, in two, three and even four sections, held by hinges and fastened for printing by as many cross-bars, in order that by opening one section, from time to time, the operator can follow the progressive changes resulting from the action of light on the iron salts. To print, the frame should be placed in the light in such a manner as the luminous rays fall perpendicularly upon the drawing or cliché. The reason of this is obvious, since the sensitive paper is not in direct contact with the design, but separated by the material upon which it is drawn.

During the insolation—whose time depends necessarily from the more or less transparency of the cliché, and, also, from the intensity of the light(7)—the paper assumes first a violet tint, which gradually intensifies to a dark shade; then this tint fades, becomes brownish, then pale lilac, while the parts under the lines—that is, the design—upon which the light has, therefore, no action, are visible by keeping the original yellow-green tint of the prepared paper. It is when the lilac color is produced that the exposure is sufficient.