Squeak...I'm digging back into photography history, but in the mid-to late 1800's surfaces to be printed on (images exposed) were hand-coated with a silver oxide surface. A brush was used. The phot sensitive surface was thick enough that, when looked at at an angle, you could see the layers as the image was exposed at differewnt levels (darker was deeper). Seeing the image would help, but I'm not really a historical expert, even though we're a fairly large regional photography house.


russ