Collodion Process - Collodion Emulsion Preparation Example

Collodion Emulsion Preparation Example

Below is an example of the preparation of a collodion emulsion, from the late 19th century. The language has been adapted to be more modern, and the units of measure have been converted to metric.

4.9 grams of pyroxylin are dissolved in 81.3 ml of alcohol, 148 ml of ether.

13 grams of zinc bromide are dissolved in 29.6 ml of alcohol. Four or five drops of nitric acid are added. This is added to half the collodion made above.

21.4 grams of silver nitrate are dissolved in 7.4 ml of water. 29.6 ml of alcohol are added. This is then poured into the other half of the collodion; the brominized collodion dropped in, slowly, while stirring.

The result is an emulsion of silver bromide. It is left to ripen for 10 to 20 hours, until it attains a creamy consistency. It may then be used or washed, as outlined below.

To wash, the emulsion is poured into a dish and the solvents are evaporated, until the collodion becomes gelatinous. It is then washed with water, followed by a washing in alcohol. After washing, it is re-dissolved in a mixture of ether and alcohol, and is ready for use.

Emulsions created in this manner could be used wet, but they were often coated on the plate and preserved in similar ways to the dry process.

Collodion emulsion plates were developed in an alkaline developer, not unlike those in common use today. An example formula follows.

Part A:

Pyrogallic acid 96 g Alcohol 1 oz.

Part B: Potassium bromide 12 g Distilled Water 30 ml

Part C: Ammonium carbonate 80 g Water 30 ml

When needed for use, mix 0.37 ml of A, 2.72 ml of B and 10.9 ml of C. Flow this over the plate until developed. If a dry plate is used, first wash the preservative off in running water.