Judy,
Thank you for your commemts. I tried soaking the card as you suggested,
and as far as I could see the clay did not wash out. I also tried
coating the dry card with two gum formulations, one on gum arabic, the
other on poly vinyl alcohol,( I could'nt find my ferric ammonium citrate
for the Cyanotype), neither one wetted the card very well, even with the
addition of a wetting agent.
This was perhaps because the clay rendered the card somewhat
hydrophobic. The next test is to give the card a slight soak in water
and try a gelatine sub coat, before going any further.
I don't know what the archival qualities would be, but as I have about
150 square yards of the stuff, it seems worthwhile persevering with
it,as it would be handy for tests.
Alex.
Alex Nanson
Gloucester UK