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 [pg 68] 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.