The substrate in gum does two things. One is that it stabilizes the paper.
Paper when wet stretches and when it dries, it shrinks, and not always
exactly the same. The other is that it allows only one side to become wet.
When only one side is wet it can be dried rapidly with a hair drier. I found
that with the substrate, I could make very short exposures, with very short
development times. We're talking here about 2 or 3 minute exposures and
similar development times. With short exposures, short development and fast
drying, I've had students make 8 to 10 coats on 4 or 5 or more prints in an
evening workshop. The print can be built up in thin layers with absolute
registration, the color and contrast can be adjusted in increments.
Heavy paper is more stable than light paper, but when taped down, both sides
get wet. Our experience showed that applying a hair dryer to a taped down
gum caused the paper to buckle, and steam to push the print up in the
center, the drying was not even and water would puddle in the buckles
causing uneven development.
In traditional gum making the tape mentod will work, but the substrate
allows you do heretical things to the gum print.
Dick Sullivan
Bostick & Sullivan
1541 Center Dr.
Santa Fe, New Mexico
87505