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Collodion Emulsion

solution, silver, alcohol and added

COLLODION EMULSION (unwashed). – In this procegs the emulsion is not washed until after the plates are coated. The first operation is the manufacture of the collodion, which is done after the following formula : Sulphuric ether (.72o) 7 ounces Alcohol (.820) 4 ounces Pyroxyline (high temperature) 7o grains Zinc bromide 120 grains The pyroxyline is described as "high temperature." This will be clearly explained under Pyroxyline.

The ingredients•of the above formula should be mixed in the order that they are given, and allowed to stand one clear day.

One hundred and eighty grains of silver nitrate are then dissolved in a test tube with 90 minims of boiling distilled water. In another test tubej.4, ounces of alcohol are boiled, and when both solutions are at their boiling points add i ounce of the alcohol to the silver solution. The test tube containing the silver solution, the tube containing the remaining ounce of alcohol and the bromized collodion, are next all removed to the dark-room—a room lighted only by yellow light. The silver solution is then added drop by drop to the collodion, which is kept violently agitated with a glass stirring rod. When all the silver solution has been added, the remaining ounce of alcohol is poured into the tube to dissolve the crystallized silver, which will probably form, and it is then added to the emulsion. The whole is then well shaken, and the

collodio-bromide emulsion, which is now formed, is left several days to ripen.

When thoroughly "ripened " the emulsion is filtered through a funnel containing a tuft of cotton-wool.

Glass plates thoroughly cleaned and polished are provided with an albumen substratum or an edging of india rubber solution. The method of making the substratum is as follows : The white of an egg is beaten up in 40 ounces of water, and a small quantity of ammonia is added until its smell is distinctly perceptible. The whole is then allowed to stand, and filtered carefully. This solution will keep for a great length of time, provided a little ammonia be added when necessary.

With this solution the clean and wetted glass plate is flowed twice over and dried. The plate is then coated with the collodion emulsion, and when it is set the plate is plunged into distilled water, and afterwards washed in clean water until all trace of greasiness has disappeared. The preservative is then applied and the plates dried for use.