Wax was applied to paper negatives to increase translucence, thus shortening the printing time and improving image resolution (Talbot, 1841). Waxing the paper before sensitization (Le Gray, 1850) improved resilience and keeping properties: once waxed and prepared with potassium iodide and a casein or rice water binder (which prevented oxidation of the image-forming chemicals), the paper could be stored indefinitely. It could remain stable for two to three weeks after sensitization with acidified silver nitrate, and did not have to be developed immediately after exposure. These advantages recommended such negatives to the travelling photographer.
— Hope Kingsley
