This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Gun Cotton (Neg. Cotton) ...
Preparing The Plain Collodion. A simple method for preparing the collodion is as follows: Dissolve 6 grains of gun-cotton (negative cotton) to every ounce of equal quantities of alcohol and ether. In preparing the above formula for 20 ounces of collodion you would proceed as follows:
886. Place in a 32-ounce narrow-necked bottle, 120 grains of negative cotton. It will be found necessary to pull the cotton in small threads in order to insert it in the narrow neck of the bottle. After all the cotton has been placed in the bottle, add 10 ounces of alcohol and 10 ounces of ether. Shake until the cotton is entirely dissolved. This constitutes your plain collodion.
Iodizing The Collodion. The collodion is iodized by adding to the above plain collodion solution:
Iodide of Cadmium
iodide of Ammonium
Bromide of Ammonium......
Shake until all ingredients are dissolved. The collodion works best when allowed to stand for a day to ripen before use.
888. It may become necessary at times to change the proportion slightly. For example, in cold weather you may slightly increase the ether and proportionately decrease the alcohol. By changing the proportions of iodide and bromide more density or more detail may be produced -less bromide will give more contrast, more bromide will give more detail, etc.
Preparing The Silver Sensitizing Bath. The preparation of the silver bath is, practically speaking, a very simple matter, yet there are certain points which are important and must be remembered. The bath must be either neutral or acid, never alkaline, and the amount of acidity or neutrality is governed entirely by the compound used in forming the collodion. For example: If iodide alone is used, so that the collodion is simply an iodized collodion and the sensitive salt in the film consists wholly of silver iodide, then the bath may be in a neutral state. If the collodion has been bromo - iodized according to the formula given above, the bath must be slightly acid. It is advisable for the beginner to use the bromo - iodized bath, as given above, and prepare the sensitizing silver bath acid, using nitric acid, C. P., for the purpose. Nitric acid will prevent spontaneous or independent reduction of the silver, thus keeping the shadows clear and free from chemical fog.
890. The quantity of silver solution to be prepared will depend entirely upon the size negatives to be made; in other words, prepare sufficient to fill the glass receptacle in which the plates are to be sensitized. The following formula will be found to give excellent results and will make sufficient solution to cover an 8 x 10 plate:
Pure Nitrate of Silver, crystals
Distilled Water ..................
.......80 fluid ozs.
Nitric Acid, C. P..................