The preparation of plain collodion employed is the same as that described at [page 53].
Developing Solution for Negatives.
| Rain or distilled water | 6 | ounces. |
| Protosulphate of iron | 300 | grains. |
| Acetic acid | 2 | ounces. |
A little alcohol may be added to make it flow more evenly over the plate—say 1 oz.
This solution can be kept in a pint bottle, and should have a funnel devoted solely to the purpose of filtering it. One of the most convenient dishes for receiving this solution, when poured over the plate, is a bowl with a lip to it, as it can be readily poured back into the funnel.
The mode of employing this developer is the same as that for positives, described at [page 133]. It may be used an indefinite number of times, but should be kept clean; it soon assumes a red color.
Re-developing Solution.
This solution is for the purpose of giving increased intensity to the negative, but as its use in the hands of beginners is attended with some difficulty, I would not recommend the operator to try it until he has had considerable experience in the developing process, or he will undoubtedly spoil his proofs. Its use requires promptness of action and quick observation.
The following is the formula for its preparation: