Well.... I didn't want to put it quite that directly, but now that you have
>I think the real underlying "secret" to the Fresson process lies in
>formulas which are a mixture of gum and gelatin. The proportions change
>the characteristics of each layer where the gum adds to the adhesive
>quality and the gelatin the cohesive quality. In addition this
>gum/gelatin ratio affects grain, tonal transition and the ultimate
>maximum shadow density.
Ultimately I think you are right and the answer lies in the "mechanical"
structure of the coating as opposed to the "chemical", though the two are
intertwined of course. My theory is that the structure allows for some
tunnels from the surface down to the paper level which allows water in to
dissolve the pigment bearing colloid from the soft bottom layer. The
tunnels allow the water in and the pigment and colloid out. The hard top
"roof" layer is flexible enough to collapse without breaking. This may or
may not be the "Fresson principle", and who cares what it is so long as it
makes pretty pictures. This seems like a logical principle from which to work.
If there is a fancy machine then my guess is that it deposits the pigmented
colloid in a fine dispersion of dots and then a roof coating and then
tunnels through the roof.
I don't know whether the 4-color is a single coat system or not but if it
is then the machine is probably using using as Lumiere plate principle and
putting down dots in that fashion.
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