According to the _Encyclopedia of Photography_, Herschel claimed that
the yellow japonica was most sensitive, then came the "blue tincture of
the double purple groundsel", but I'm sure there are many natural colors
that would work (finally something to do with "fugitive" pigments?!).
The real point is, as there is no processing and therefore no _fixing_,
these are not permanent. Yes, it's an absurd thing to pursue, but it
would make a fun experiment to open an alt-process workshop, if it
didn't take so long. (Supposedly a more alkaline mixture is more
sensitive.)
As for alcohol, I don't know. For all my involvement in these processes,
I'm still a poor chemist. Denatured alcohol got me some nice colors. As
for paper, it should be thin - the books say to wet the back before
applying, I assume to help the mixture soak in. (I haven't tried
sizing.)
What I'd love is the chemical know-how to jazz this up just enough to be
fun. For now, well, I just started three days ago. I'll let you know
what's up in a month - after the exposure's done.
Dan Estabrook
P.S. There are examples of Anthotypes at the Harry Ransom Humanities
Research Center at the University of Texas in Austin, and at the Museum
of the History of Science, Oxford. Haven't seen 'em...