This formula has never before been published, and must be prepared as directed.
Alcohol and ether equal parts; gun cotton sufficient to make a moderately thick film, say 5 or 6 grains to the oz.; put the cotton in the ether first; when it is well saturated, pour in the alcohol. To which add:
| Iodide of Ammonium | 4 grains to oz. |
| Iodide of Cadmium | 2 |
| Bromide of Cadmium | 1 |
| Bromide of Copper | 1 |
The latter ingredient can only be had in aqueous solution, I believe, and requires close calculation to get at the right quantity.
This formula gives 8 grains of salts to the ounce of collodion, and would require a silver solution of 50 grains to the fluid ounce to balance properly.
The silver solution may be prepared as per directions on page 29, under the heading—The Negative Bath.
HOW TO COAT PLATES.
The ferro-plate is held between the thumb and first two fingers of the left hand. The collodion bottle is held in the right hand, and the collodion is poured on the right upper end of the plate, flowed to the left upper corner, by deflecting the plate in that direction, and then down the left side toward the hand, and the excess run back into the bottle from the right lower corner, when it has all run off, the plate should be gradually brought to a perpendicular position and rocked from right to left, that is, perpendicular to the end, p18 then to the side, until the film has set or become fixed, which may be ascertained by touching the film at the lower corner of the plate, when, if it breaks and does not run farther, it has set and should, without delay, be immersed in the silver solution, where it should remain until it has become fully sensitized, which will be in from 2 to 5 minutes.
The plate should be lowered into the bath by one continuous motion; any stoppage will cause a line and spoil the plate.
The plate is sensitized when on removing it from the bath it presents a smooth, yellowish surface; if it shows lines as of water running off a greasy surface, it is not coated; return it to the bath.