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Mounting Canvas

cap, prints and rubber

CANVAS, MOUNTING ON.—Albumen, or other prints can be mounted on canvas. First soak the canvas in a gelatine or glue solution, then sketch upon a wooden frame. When dry and perfectly tight, the prints can be readily mounted with starch paste. This is a convenient method when large prints are to be carried about. They can be handled carelessly without fear of being torn.

CAOUTCHOUC•—An American-Indian word for the substance known also as indiarubber. A solution of caoutchouc is sometimes employed for mounting gelatino-chloride prints so as to preserve the gloss. It is not an advisable method as the rubber after a time be- 4 comes hard, crumbles, and the print leaves the mount either wholly or in part. It is also used in the Woodburytype process. The best india rubber solution is made by cutting a block of rubber in two, extracting the centre portions and dissolving them in anhydrous benzole. It is also employed as a substratum in certain processes.

CAP.—The leathern covering fitting on to the end of the lens, which protects it from dust and shuts out the light when required. If an instantaneous shutter is not used, the

exposure is usually made by removing and replacing the cap. It is therefore necessary that the cap should fit easily on to the hood of the lens. If too tight, it is possible that, in removing, the camera may be caused to vibrate, while. on the other hand, if too loose, it is likely to fall off, or to ; allow stray rays of light to enter the camera and produce t fog on the sensitive plate. It should be lined inside with black velvet, and it is a good plan to attach it to the camera with a piece of string to prevent its being lost. For the better preservation of lenses it is well to have a cap to fit both ends. A cap fronted with yellow glass is very useful when enlarging with a lens. It enables the operator to readily adjust the sensitive paper to the image without fear of fogging.