CHAPTER VI. WASHED SENSITIVE PAPER.
Foa some clnsses of work sensitized paper may be washed with · advantage previous to drying, and there is much economy in this plan, ptuiicularly in hot weather, since it keeps of a p11rer white for a much longer period than where the silvf'r nitrate is allowed to dry on the surface. It may not be out of pluce to call attention to the action of silver nitrate on the paper. H a stick of lunar caustic l:·e applied to the skin when dried, there is a peculiar burning effect produced, and even in the dark the cuticle becomes discoloured, though not black. In tne albumenized paper we have albumen and the gelatine sizing, and these . substances behave somewhat like the skin. The gelatine particularly will become oxicized at the expense of t.he 8ilver, a reddish organic oxide being formed; and again, if the silver nitrate be . alkaline or strictly neutral, we have the same action occurring as when we precipitate metallic silver by means of an alkali, and an organic body such as sugar of milk. The gelatine takes the place; of the latter. When the free silver nitrate is removed, the tendency for the spontaneous darkening of ~he paper is mueh diminished, since the chloride and clbuminate of silver are much· less ·readily reduced than the nitrate. The following plan, is adopted for washing the paper :-The paper, after :floating, is_· drawn twice rapidly through a dish of rain or di~tilled water,