The DARKROOM COOKBOOK, Third Edition

156 THE DARKROOM COOKBOOK
layer (as used in all commercial gelatin-based photographic papers) contains an inert
white solid suspended in hardened gelatin. Baryta coated papers are becoming more
diffi cult to fi nd as traditional silver based photographic papers fall from the marketplace.
If uncoated papers are used, the solvents in the collodion emulsion will fl ow right
through the paper fi bers.
Cut a sheet of glass an inch larger on all sides than the paper you wish to coat. Desharpen
all the edges with a sharpening stone to prevent accidental cuts. Fold up a ½
inch margin on all the edges of your paper and carefully secure the paper onto the glass
sheet using small pieces of masking tape.
If you already do the wet collodion process, the following technique is the same for
coating plates. Holding the glass supporting the paper in one hand, pour the collodion
emulsion onto the center of the paper. Tilt the paper so that the emulsion fl ows to all
the corners covering the entire sheet. Pour off the excess emulsion from one corner
back into the bottle. This draining step may result in diagonal lines forming in the surface
of the coating. To prevent these, rock the plate from side to side during the draining
step. Keep the corner from which the collodion was drained lower than the rest
until the collodion starts to set to a fi rm gel.
Once the collodion has set, carefully detach the paper and pin it up by one corner
to dry in a darkened room. Because collodion emulsions are solvent based, the emulsion
will dry to a hard fi lm in minutes. Once coated, it can be printed immediately or preserved
for days in a light tight box. Collodion printing out paper is toned and processed
using the same technique as described for salt, albumen or gelatin chloride papers.
The only difference between collodion coated papers and all the others is that during
processing the paper may curl slightly. This is because the collodion side will not
easily absorb the processing solutions. This effect can be corrected by using solutions
slightly warmed or a smaller quantity of solutions in each tray.