Film Film Photography
imitated water-marking by passing a sheet of plain paper between rollers together with one of his gelatine reliefs (see Woodbury-type). Those parts of the sheet which were subjected to most pressure became of greater transparency than the rest. Wood-bury called this process Photo-filigrane. Instructions for making an imitation water-mark, by photographic means, from any original water-marked sheet of paper will be found in The Amateur Photographer for December 7th, 1900, p. 452.
Film. The thin pellicle or skin of sensitive material on plates or paper is generally spoken of as the film.
To Remove Old Films. Nothing is better for quick removal than glacial acetic acid made into a cream with pumice-stone powder and applied with a tuft of rag, the acid instantly dis-solving the film, and the pumice powder acting as a mechanical means of removing it. When time is not an object, soaking in a weak solution (1 to 40) of caustic soda is a useful method.
To Clean the Film from the Back of Plates. Few plate manu-facturers coat their plates so carefully but what some small smears of emulsion get on the back of plate. To remove this, when the plate is thoroughly dry, place it face downwards upon a pad of blotting paper, and use a little salt with a moistened rag. The salt must not be allowed to reach the front of the plate.
Film Photography. The disadvantages of glass when used as a support for the sensitive material - which are its weight, its bulk, and liability to fracture - have induced many experimenters to search for a light, flexible support which might be used as a substitute. Thirty years ago wet collodion was used, and on the introduction of gelatine emulsions the search for a substitute received great impetus. Woodbury, in 1871, suggested Tollable films; Warnerke, in 1876, used gelatine emulsion spread on paper, from which it was afterwards stripped ; Pumphrey, Vergara, and others followed; but it was not till the introduction of Celluloid (q.v.) that a satisfactory stage may be said to have been reached. Films have not only the advantage of extreme porta-bility, but also that of giving negatives practically free from halation ; still, owing to the flexibility of film and a tendency to curl in the liquid baths, some notes as to handling will be acceptable.