Chapter 5

Bitumen of Judaea 8 parts Yellow wax 2 parts Benzole 40 parts Turpentine oil 60 parts (filter)

then etched as done to engrave in the aquafortis manner, the corrections being made by applying with a brush some of the above varnish on the defective parts, which are worked over when the varnish is dry.

The tools are simply needles of various thickness ground in sharp square and round points of different sizes.

When the etching is finished, the parts which should form the ground, or white parts of the design, being covered with the bitumen varnish is non-actinic, or, in other words, does not admit the light acting on the sensitive plate preparation employed to reproduce the design, except by an exposure a good deal longer than that necessary to reduce the metallic salts.

The engraver will see at once that, although it greatly simplifies the copying work and, consequently, saves much time, this process does not, however, bind him to any rules and leaves him perfectly free to follow its inspirations and make such alterations as he thinks proper to produce artistic effects; in a word, the reproduction will no more be a picture taken by a mechanical process, so to say, but an original drawing reflecting his talent and characteristic manner.

A similar process much employed by photo engravers, and presenting the same advantages, is to convert an ordinary photograph on paper—or a blue print, as devised by the writer—into a design in lines by drawing with India ink, or the special ink of Higgins, and, this done, to wash off the photographic image, the design being afterwards reproduced by the ordinary processes as a negative or a positive cliché.

When the photograph is a silver print especially made for the purpose in question and, consequently not _toned,_ but simply fixed in a new thiosulphate (hyposulphite) bath, and well washed—it is bleached by flowing over a solution of—

Bichloride of mercury 5 parts Alcohol 40 parts(13) Water 100 parts

If the photograph has been toned, i.e., colored by a deposit of gold, or if it was fixed in a thiosulphate bath in which toned prints have been fixed, then the image is dissolved by treatment in a solution of potassium cyanide in alcoholized water.

When a blue photograph is reduced, it is advisable before drawing upon it to first reduce its intensity by a prolonged immersion into water. Pale blue is a very actinic color which is not reproduced in photography, except by the ortho-chromatic process, or if it does, the impression being very weak, is not objectionable. When the image has not been sufficiently or not at all bleached, the blue is dissolved by an alcoholized solution of the blue solving.

THE URANOTYPE.

This process, devised by J. Wothly, in 1864, did not receive from the photographers the attention it merits, as it is always the case when a process is patented, and can be replaced by another equally practical which is not. It gives pictures of a very good tone, which are quite permanent; we have some made in 1866, which are suffered no change whatever, they seem to have been printed from yesterday.

The first process given by Wothly does not appear to be complete. It has been well described by H. Cooper and a gentleman who signs by the initial letter X.

The process published in 1865 by Wothly is as follows: A sheet of paper is sized by brushing with a paste made of 24 parts of arrowroot in 500 parts of water, to which are added a few drops of a solution of citric or tartaric acid, then coated with a collodion consisting of 100 cubic centimeters of plain collodion, a few drops of oil of turpentine and 30 cubic centimeters of the following sensitizing solution:

Nitrate of uranium 30 to 90 parts Chloride of platinum 2 parts Alcohol 180 parts

The time of exposure is about that required for paper prepared with silver chloride. The image is bluish-black but weak. After washing the print is immersed in a solution containing 0.5 parts of chloride of gold for 2,000 parts of distilled water, and then fixed in a bath of sulphocyanate of potassium, which tones the image blue-black.

It may happen that the proof is slightly tinted red. This arises from a small quantity of lime in the paper which forms uranate of calcium.

To prevent the proofs turning yellow, it should be washed in an exceedingly weak solution of acetic acid.

If, after exposure, the print is immersed, without it being washed, in the gold bath, the image becomes rose-red, but the whites remain pure. The effect is peculiar.

H. COOPER’S PROCESS (1865).

PREPARATION OF THE PAPER St. Vincent arrowroot 200 grains Boiling water 10 ounces

Crush the arrowroot to fine powder, then rub it to a paste with a little water, and let an assistant pour a few drams of boiling water while you keep stirring all the time; finally, let him add the rest of the boiling water, the operator still continuing the stirring. The paste is allowed to cool, and will be thicker when cold than when hot. Remove the upper portion entirely when quite cold, otherwise, if any left, it will give rise to streaks. The author insists upon the necessity of all these cares. Two sheets of paper are now placed side by side on a flat board, then the surface of the first is covered with the paste by means of a sponge, proceeding, before you leave it, all over the sheet in a horizontal direction; the second sheet is covered in a like manner. By the time the second sheet is pasted, the first one will be partially dry. The sponge is now drawn over each sheet, in succession, in a perpendicular direction in order to efface the streaks from the first sponging. If the paste drags in a slimy manner, it is too strong, and a fresh arrowroot must be prepared, because dilution only ends in failure. Why dry, the paper is rolled under moderate pressure, and when it lies smoothly the maximum pressure may be applied.

PLAIN COLLODION. Alcohol 12 ounces Ether 4 ounces Pyroxyline 80 grains

SENSITIVE COLLODION. Plain collodion 1 ounce Nitrate of uranium, pure 30 grains Nitrate or silver 5 grains

Add the uranium first, and as soon as it has dissolved all that it can, add a grain or two of soda, and when settled pour off the supernatant collodion and add the silver.(14) To coat the paper with collodion, use a board with a handle beneath, such as is used by plasterers. On this place a sheet of paper, the edges being turned up about the sixteenth of an inch; this enables the whole of the sheet to be covered without spilling the collodion or allowing it to run on the back of the paper.

There is a marked difference in the appearance of the prints when they leave the pressure frame. Some samples of collodion cause the picture to print of a beautiful green, others of a rich brown, and some of a yellow or orange tint. The last take the longest of all to tone, and difficultly assume the tint of well toned silver prints,(15) those printing to green or brown tone very rapidly.

After printing the pictures are placed in diluted sulphuric acid, 1 to 30 of water, until the high lights are perfectly clear and white; this takes from ten to fifteen minutes. After washing well under a stream of water, they are placed in the toning and fixing bath.

TONING AND FIXING BATH. Sulphocyanide of ammonium 1 ounce Water 12 ounces Chloride of gold 1 to 3 grains

After removing from this bath, the prints are immersed for a few moments in water, and then rapidly washed.

FORMULA FOR PREPARING THE PYROXYLINE Nitric acid, sp. gr. 1.30 12 fluid ounces Sulphuric acid, sp. gr. 36 fluid ounces 1.845 Water 8 fluid ounces Temperature 130 degrees Fahr. Time of immersion 15 minutes.

X’S PROCESS (1865). (Secrets of the Uranotype)

_Preparation of the Uranium Compound.—_Precipitate the nitrate of uranium from its solution by concentrated liquid ammonia. Let settle the precipitate, decant, and wash in several changes of water. Dissolve it by heat in pure nitric acid, _taking care not to add an excess of acid._ The ammonio-nitrate of uranium salt is then crystallized and dried. Mix a solution of 6 drams of this salt, dissolved in 3 drams of water, to a solution of 15 grains of silver in 30 minims of water, and crystallize. This salt is called _ammonio-nitrate of uranium and silver._

SENSITIZING SOLUTION. Ammonio nitrate salt 3 drams Alcohol 8 drams Distilled water 15 drops Nitric acid, pure 1 drop

_Plain Collodion.—_Dissolve in a small quantity of ether 1 dram of Canada balsam and 1 dram of castor oil, filter and let evaporate the solution to the consistency of oil.

Of this, add 10 minims to a collodion made of

Alcohol 10 ounces Ether 20 ounces Pyroxyline 220 grains

SENSITIVE COLLODION Plain collodion 12 drams Sensitizing solution 6 drams Nitric acid 2 or more drops

Keep this collodion in the dark, as it is quite sensitive.

PREPARATION OF THE PAPER Arrowroot, pulverized 1 ounce Water 32 ounces Solution of acetate of 10 drops lead

Heat to 100 deg. Fahr. and then add four ounces of albumen. The paper is floated on this solution for five minutes and hung up to dry. The sizing may also be applied with a sponge in the manner often described.

The proofs should be slightly over-printed and, before toning and fixing, placed for about ten minutes in the following solution:

Distilled water 40 ounces Acetic acid 1 ounce Hydrochloric acid 1 ounce

After washing in several changes of water, the proofs may be toned in any toning bath, and then fixed with sulphocyanide of potassium, washing afterwards in the usual manner.

THE PLATINOTYPE.

This process, discovered by William Willis,(16) yields very fine impressions which wholly consists of platinum and are, therefore, chemically permanent. It has been described theoretically and practically by Pizzighelli and Kübl in a paper for which the Vienna Photographic Society has awarded the Voightlander prize.(17) The following is an abridgment of this important process, as described by the authors:

The paper, calendered or not,(18) is sized with gelatine or arrowroot. The color of the proof with the latter size is brownish black, and bluish black with the former.

To prepare the gelatine solution 10 parts of gelatine are soaked in 800 parts of water and then dissolved at a temperature of 60 deg. C. (140 deg. Fahr.), when 200 parts of alcohol and 3 parts of alum are added and the solution filtered.

To prepare the arrowroot solution 10 parts of the substance are powdered in a mortar with a little water and mixed to 800 parts of boiling water, added gradually in stirring. After boiling for a few minutes 200 parts of alcohol are added and the mixture filtered.

These solutions are employed warm. The paper is immersed for two or three minutes and hung up to dry in a heated room, then immersed a second time and dried by hanging it up in the opposite direction, in order to obtain an even coating.

The potassic platinic chloride is an article of commerce. It should be soluble without residue in 6 parts of water and without acid reaction. In this proportion it constitutes the normal stock solution employed in the various formulas.

The standard ferric oxalate solution is also found in commerce. Treated by potassium ferricyanate it should not be colored blue, nor become turpid when diluted with one-tenth part of water and boiled. The former reaction indicates that it contains no ferrous salt, and the latter no basic oxalate.

The authors give the following instructions for preparing the ferric oxalate solution, to which they attach much importance:

Five hundred parts of ferric chloride are dissolved in 5,000 parts of water and heated to boiling, when a solution of soda is added until the liquid becomes alkaline.(19) About 250 parts of caustic soda are generally employed for this purpose. The precipitate—ferric oxide—is now washed in warm water until the last washing water is quite neutral to test paper, then drained and mixed with 200 parts of pure crystallized oxalic acid. The mixture is then allowed to stand in the dark for several days at a temperature not exceeding 30 deg. C. (86 deg. Fahr.) At first the solution from green turns to a yellow green, and finally becomes almost brown. At this moment the excess of ferric oxide is filtered out and the liquor submitted to a quantitative analysis, the result of which leads to ascertain the quantity of ferric oxalate in 100 parts of the solution and the excess of oxalic acid. The solution should then be diluted with distilled water, such as it contains 20 parts of ferric oxalate per 100 parts of water, and oxalic acid must be added in the proportion of from 6 to 8 per 100 of the ferric oxalate, taking into account the quantity of acid the solution already contains. The solution should be kept in the dark. It is altered by light.(20)

IRON CHLORATE SOLUTION Ferric oxalate solution 100 parts Potassium chlorate 0.4 parts

This solution is employed to obtain more contrasts.

PREPARATION OF THE SENSITIZING SOLUTION Platinum solution 12 parts Ferric oxalate solution 11 parts Distilled water 2 parts

This solution gives very soft tones with intense black. To obtain more brilliancy we use the following proportions:

Platinum solution 12 parts Ferric oxalate solution 9 parts Chlorate of iron solution 3 parts Distilled water 2 parts

To obtain results comparable to those which the silver printing out process gives, the following mixture is employed:

Platinum solution 12 parts Ferric oxalate solution 8 parts Chlorate of iron solution 4 parts Distilled water 8 parts

For very weak negatives, reproductions of drawings, etc., we use—

Platinum solution 12 parts Chlorate of iron 11 parts Distilled water 2 parts(21)

To obtain proofs not completely black, as, for example, reproductions of lead drawings, the solution may be diluted with half or the whole volume of distilled water. But if the solution be applied on little absorbent surfaces or on paper strongly sized it is not advisable to dilute it.

_Preparation, of the Paper.—_The paper should be kept slightly moist in order that it does not too completely absorb the sensitizing solution. Therefore, when the atmosphere is very dry, it is well to keep the paper in a damp place, in the cellar for example. Before sensitizing, which should be done by a very diffused light, a quantity of the solution proportionate to the surface to be sensitized (about 15 c.c., for a whole sheet of Rives’ or Saxe paper) must be measured, and spread with a large brush(22) on the paper fixed with drawing pins on a board covered with a sheet of blotting paper. When well impregnated, the paper is hung up to dry in the dark room, and as soon as the apparent dampness of the surface has disappeared, it should be dried immediately at a temperature of 30—40 deg. C. (86—101 deg. Fahr). If the paper be dried too rapidly the sensitive compound remains on its surface, and in developing the image does not come out well. If, on the other hand, the drying is too slow, the solution penetrates too much in the paper and the image is wanting of vigor and does not appear very sharp. One cannot depart from this rule that the desiccation from the moment the solution has been applied until the paper is dry should last no more than from twelve to fifteen minutes.

The sensitized paper is hygroscopic and must be preserved in a calcium box. _It is a conditio sine qua non that the paper must be quite dry before, during, and after printing, to obtain good results._ Dampness is the greatest enemy in this process.

For printing a pad of India rubber should be placed over the platinum paper to prevent it from attracting the atmospheric moisture, and in damp weather it is even advisable to cover it with several sheets of blotting paper previously heated before the fire.

The platinum paper is at least three times more sensitive than the silver paper used in the printing-out process, under the reductive action of light the yellow color of the prepared paper turns brown and then becomes of a lighter color, nearly orange, so that the darker parts of the image often appears more luminous than the dark half tints. No rule can be given to regulate the insolation, but after a few trials it is easy to judge when it is right by observing the progress of the reduction and the color of the image. The orange color indicates the complete reduction of the ferric oxalate. When the details in the lights are _faintly_ visible, the exposure is generally right.

The developer consists of an almost saturated solution of potassium oxalate _acidified by oxalic acid,_ and for use heated to 80—85 deg. 0. (176—184 deg. Fahr.),(23) in an agate glazed iron tray placed upon a water bath at the above temperature. By simply drawing the proof over it, the image is at once developed.(24)

When the proof is thought to be over-exposed, the oxalate solution can be employed at a lower temperature. If, on the contrary, it is under-exposed, the solution may be heated even to the boiling point.

The developer can be used over and over again. _It should always have an acid reaction._

According to Mr. Borlinetto a sepia tone is obtained by using the following cold developer:

Saturated solution of 120 parts potassium oxalate Saturated solution of 13 parts copper chloride Oxalic acid 1.5 part

After developing the proofs are _immediately_ immersed for fixing in a solution of hydrochloric acid, 1 to 80 of water, renewed so long as the paper is tinged yellow (about three times), leaving the proofs ten minutes in each solution. Lastly, they are washed to remove the acid.

The platinotype has been still improved by Captain Pizzighelli, who devised the following methods of operating by which the impressions are obtained by the continuous action of light, that is, without development, thus rendering the platinotype just as simple as the ordinary printing-out silver process.

In these new processes to the sensitizing solution is added the alkaline oxalate, which effects the reduction of the platinous salt during the exposure to light. Consequently the prepared paper is insolated until the image appears as it should be, or—which is exceedingly useful in cloudy weather—until it is entirely visible but still deficient in delicate half tones, for in the dark the action proceeds and the image developing itself will be found finished in a period which may extend to a few hours. But it can be, however, developed in a few seconds by immersion in a cold or slightly warm solution of sodium carbonate, 1:25 of water. The image is fixed as directed in the foregoing process.

The paper, prepared exactly as in the former process and kept in the calcium box until wanted for use, should not be employed quite dry, but allowed to absorb a little moisture by hanging it in the dark room. Hence, the India rubber and other protecting pads can be dispensed with. They are even objectionable, for dampness is absolutely necessary to promote the chemical changes by which the image is developed.

A. AMMONIO-FERRIC OXALATE SOLUTION Ferric oxalate solution 100 parts Neutral ammonium oxalate 18 to 20 parts

B. SODIO-FERRIC OXALATE SOLUTION Ferric oxalate solution 100 parts Neutral sodium oxalate 15 to 18 parts

To prepare these two solutions the ammonium or sodium oxalate is dissolved by small quantities at a time, and when the emerald color due to the formation of the double oxalate commences to darken, the saturation being then complete, no more of either salt should be added. The solution is now well shaken with 3 parts of glycerine, allowed to settle and filtered.

Any one of the double oxalates can be used. The ammonium tends to produce softer pictures and bluish tones. To obtain more contrasts a little potassium chlorate may be added.

C. IRON CHLORATE SOLUTION Solution B 100 parts Potassium chlorate 0.4 part

D. MERCURIC SOLUTION. Mercuric chloride 20 parts solution at 5:100 Sodium oxalate solution 40 parts at 3:100 Glycerine 2 parts

SENSITIZING SOLUTIONS. FOR BLACK TONES. Platinite solution, 1:6 5 parts Solution B 6 parts Solution C 2 parts

FOR SEPIA TONES. Platinite solution, 1:6 5 parts Solution C 4 parts Solution D 4 parts

Intermediate tones are obtained by diminishing the dose of C and replacing it by an equal volume of B. For this process the paper should be sized with

Arrowroot 2 parts Sodium oxalate at 3:100 100 parts

To dispense with this preliminary sizing Captain Pizzighelli adds gum arabic to the platinite solution, whereby the sizing and sensitizing are done in one operation.

The gum arabic solutions are prepared as follows:

E. Gum arabic in 40 parts powder Sodium ferric 40 parts oxalate solution, B Sodium oxalate 100 parts solution at 3:100 Glycerine 3 parts

Place the glycerine and the gum arabic in a mortar, then, stirring with the pestle, dissolve by adding, little by little, the mixture, heated to 40—45 deg. C. (104—113 deg. Fahr.), of the solution of sodium ferric oxalate and sodium oxalate. Let stand for about two hours and grind again to dissolve entirely the gum arabic. Filter through muslin.

F. Mercuric chloride 20 parts solution, 5:100 Sodium oxalate solution, 40 parts 3:100 Gum arabic in powder 24 parts Glycerine 2 parts

Dissolve as said above.

SENSITIZING SOLUTIONS. FOR BLACK TONES. Platinite solution, 1:6 5 parts Solution E 6 parts Solution C 2 parts

FOR SEPIA TONES. Platinite solution, 1:6 5 parts Solution C 4 parts Solution F 4 parts

Mix just before use. The solutions do not keep. The paper prepared by either one of these two processes can be exposed as in the _old_ process, and the image developed bythe hot oxalate solution.

The preparation of wood, canvas, etc., for the platinotype printing need not to be described; it suggests itself.

CAUSES OF FAILURES.

_The images are veiled._

This defect may result from various causes, viz.:

1st. The stock ferric oxalate solution is impaired by a partial reduction of the ferric salt into ferrous oxalate. The solution should be preserved in an orange colored vial, and kept in the closet of the dark room. It should be tested from time to time for the ferrous salt with a solution of potassium ferricyanate. If it does not contain any ferrous oxalate it can be used by adding to it a little of the iron chlorate solution. 2d. The paper has been exposed to light during the sensitizing or the subsequent operations. One should bear in mind that the platinum paper is twice more sensitive than silvered paper. 3d. The sensitized paper has been dried at a temperature above 40 deg. C. (104. deg. Fahr.) 4th. Over-exposure.

_The proofs are not sharp._

1st. The sensitive paper has absorbed moisture. 2d. It is too old. The paper cannot be kept good for over six weeks, unless special care be taken.

According to Mr. Bory, the sensitive paper altered by keeping is restored to its original good quality by simply brushing it over with a solution of 0.05 parts of potassium chloride or the same quantity of potassium chlorate in 100 parts of distilled water, or a mixture of these two solutions, or one of iron chlorate.