| Iodide Ammonium | 192 grains |
| Bromide Cadmium | 128 |
| Bromide Potassium | 96 |
| Ether and Alcohol | 32 oz. each |
| Cotton | 320 grains |
The preceding formulæ are for portrait work in studio. For other work, such as outdoor views, p28 landscape or architectural, or for copying engravings, etc., certain modifications of the collodion, to produce greater intensity or more contrast, are desirable. Collodion suitable for such purposes can always be purchased from the photo stock dealer, in quantities desired, and for that reason it is not best for the amateur nor the professional photographer either, to prepare small samples for special purposes. If it should, however, be found at any time necessary to prepare such a collodion, the second formula of Negative Collodion A will be found suitable for views of buildings, copies of engravings and such like work.
It was at first thought to be unnecessary to give a formula for the preparation of pyroxiline or gun cotton, as no individual not in the business can possibly produce an article that can be in any way compared to that made by manufacturers of skill and experience.
For the benefit of any one wishing to experiment, this formula is given:
FORMULA FOR MAKING COLLODION COTTON.
| Sulphuric Acid | 6 oz. |
| Nitric Acid | 4 |
| Water | 2 |
Mix and the temperature will rise to 170° F.
Inmerse dry cotton wool (best long fibre), be sure wool is dry, draw it in long flakes and pull it under acids with a stout glass rod; do not crowd in too much, take care that each tuft is well wetted with the acids before putting in a fresh tuft. Carefully cover the vessel and put it where any slight fumes may escape; leave it for at least 12 hours—20 hours will not spoil it. When ready, lift cotton out and plunge it p29 into a large quantity of water, quickly separating the tufts with glass rods, wash in changes of water, until no acid is left, then wring the cotton in a coarse towel until dry as possible and pull it all apart and place in the air to dry.
COLLODION WITH ABOVE.
| Alcohol | 5 oz. |
| Ether | 10 |
| Cotton | 100 grains |