In response to your questions:
1. =D2Do you keep heating the water? In my experience after the first 10
minutes temperature has dropped considerably. In fact adding a whole
lot of paper in itself drops the temperature. How many sheets do you
shrink at a time?=D3
Well, during the Las Vegas Summers the ambient temps in the studio=20
do not require re-heating the water. During the Winter, however, I do=20
re-heat the water. I=D5m using an eight inch deep heavy plastic bus tray=
=20
that I keep covered during the soak. My average paper size is 11=D3 x 14=
=D3=20
and I typically will process fifteen to twenty sheets at a time. I add=20
the paper to the tray while filling it; I have a hose attached to the=20
faucet that allows me to wet both sides and dislodge air bubbles. Water=20
temp 130F
2." I'm curious about the baking after the initial hot water shrink,=20
about why baking the dry paper shrinks it still more... Have you tried=20
just the baking alone? Have you measured further shrinkage after the=20
baking? When I measured, I found that the paper might either shrink or=20
expand again after re-wetting and drying, presumably according to room=20
temperature & humidity".
I=D5ll readily admit to my often casual and empirical approach to gum=
=20
printing and likewise confess to not having done any tests that are in=20
any sense clinical. I nonetheless have a portfolio of prints that=20
suggest my method of working has at least personal merits. Have not=20
thought to try the platen heating alone. I believe your other concerns=20
are in part correct; but I=D5m thinking that my hot soak and heating=20
effectively reduces the degree by which the paper will be affected by=20
re-wetting, humidity, and drying........it appears to me that after=20
multiple printings my paper consistently settles into a stable=20
dimension. If we shrink a cotton rag, though it is still susceptible to=20
expansion and contraction, I don=D5t think it can expand back to its=20
original dimension.
3." When you say "hard sizing", you mean a bath in a hardener?
Correct. A formalin/gelatin final size.
4. "It occurs to me that the difference between our experience with the pap=
er
may be due, at least in part, to the fact that you use several coats of
size (2?, 3?) which may itself be what makes the paper very rigid.... it's
embedded with hardened gelatin. (I use only one coat of gelatin,
because I prefer that surface for working on.)"
I prefer to tray size the paper twice. First with plain gelatin,=20
hang dry then heat, and then with the formalin /gelatin hardener, again=20
hang dry and heat.. My method of printing requires a durable sizing that=
=20
can take 6, 8, or 10 printings. Though usually after the sixth run I=20
begin to re-size via foam brush.
5. "But you said you hung the paper to dry *before* heating.... ????
Yes, but by alternate corners during processing so as to let the=20
paper stretch or move eventually from all corners. However, during my=20
print runs after development (in room temperature water) I briefly hang the=
print to let=20
the water run off. Then I place the wet prints on drying screens under=20
which I have a small space heater. The heater is set to a very low=20
temperature, the prints are about a foot from the heater, it=D5s sole=20
purpose is to expedite drying. Then 15 to 30 seconds into the platen=20
heater. This really is only to flatten the prints thus making them=20
easier to re-coat. To much heat and as you will damage the print surface=
=20
e.g., cracks and flaking.
6. "How large is "large"?
Up to 16=D3 x 20" with great success. I hope this is considered=20
a large gum!