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Stripping Films

gelatine, plate and film

STRIPPING FILMS (Collodion).—Negatives produced by the collodion process can be stripped from the glass support without much difficulty. The following is the modus operandi : The glass plate must be well polished and rubbed over with French chalk, and then polished again. It must not be albumenized. When the negative is dry strips of thick paper are pasted along the four sides, either with starch or a solution of gum tragacanth. It is then slightly warmed and placed on a previously levelled stand, and a warm solution of gelatine poured over it, sufficient to give a fairly thick film. This gelatine solution is made up as follows:— Gelatine 25 ounces Sugar. 1% ounces Water 20 ounces And is prepared by first soaking the gelatine in water until quite flabby, and then placing the vessel containing it in hot water until the gelatine is thoroughly dissolved, when it is strained through muslin and is ready for use.

In coating, a small quantity is poured over the levelled plate and spread evenly all over with a Blanchard brush or other similar contrivance. When the film is set the negative is

removed and placed in a current of cold air until the film is quite dry. When thoroughly dry all that remains to be done is to run the point of a sharp penknife all round the edges underneath the paper strips, and the negative film will leave the glass plate with a brilliantly polished and flat surface.

Old collodion negatives can be stripped sometimes, but the operation is undoubtedly a risky one, as there is always considerable chance of spoiling it during the operation. If the nega tive be a valuable one a good positive transparency should always be made before attempting the operation.

The varnish is first removed and the paper pasted round; the plate is then levelled, coated with gelatine, dried, and stripped in the same manner as already described.