In practice, you don't really need a paper support that can breathe. If you
use a plastic pigmented support, as in the Polaroid process discussed not
too long ago, your transfer will take place as long as the exposed pigment
has been allowed to absorb enough cold water to make it swell considerably.
Then, when you put this sandwich of exposed gelatin (exposed from *one*
side --important) between two waterproof layers into hot water, the
*unexposed* (soft and soluble) side of the gelatin that is against the
waterproof plastic will swell, *despite* the fact that it is not allowed to
have direct access to water penetration through the support as it is
waterproof. This goes against traditional rules, but it works. The heat
from the hot water, going through the support is enough to melt the wet
unexposed (and therefore soluble) side of the gelatin, while the other side
(exposed and no longer soluble) sticks to the other sheet of polyester.
After a few minutes in hot water, the two polyester sheets are pulled apart
and you are left with the image on one side of the polyester, which still
has to be washed off in hot water.
In the 1980s, some people with the Archival Color Co., claimed they had
"discovered" or "invented" this technique, and talked about patenting it,
but it turns out that I found old patents granted to McGraw Colorgraph
which covered these principles fully. This should be in my 1982 carbon book
_History and Practice of Carbon Processes_ Out of print:-(
Luis Nadeau
awef6t@mi.net
nadeaul@nbnet.nb.ca
Fredericton, New Brunswick, Canada
http://www.micronet.fr/~deriencg/nadeau.html
http://www.primenet.com/~dbarto/lnadeau.html#A0