Re: collotype

JFrank2642@aol.com
Thu, 25 Jan 1996 18:09:15 -0500

The collotypes that I have seen exhibit more subtlety and grace than
>photogravures, and seem to be capable of finer detail, >possibly
>it is a continuous tone process and not dependant on >generated dot
>patterns to produce continuous tones. This observation may >have to do
>with the skill of the printmakers, rather than the processes, >but I'm
>sure someone with more hands on experience from the list >will clarify this.

Collotype is supposedly a "continuous tone" process; in reality it is about
the equivlent of a 1600 dot pattern (as Luis mentioned that looks like a
brain).
The process is simple in theory, and difficult in practice.
A bichromated gelatin is exposed to UV light through a continuous tone
negative. The gelatin is "tanned" or hardened in direct proportion to the
amount of light that passes through the negative. When flooded with a
fountain solution of distilled water, glycerin and ammonia; the gelatin
swells in indirect proportion to the amount of hardening. Then when a greasy
ink is rolled over the plate; the swollen gelatin repels the ink and the
hardened gelatin accepts the ink in a "continuous tone". The inked plate is
then run though a printing press and the ink is transfered to paper. There
are many factors that are involved in the printing process. If any one would
like more information feel free to email me so we do not crowd the list.
Jim Frank
JFrank2642@aol.com