Well, you can tone your Van Dyke Brown prints blue. Right! Just mix up
(this is from memory, maybe someone will correct) 10 cc part A and 10 cc
part B of your cyanotype solutions in about 300 cc water plus 70 cc 28%
acetic acid. Works like a charm. Pointless of course, since cyanotype
itself is easier to print than VDB. (Actually, though, a very LIGHT blue
toning can often soften an ugly VDB.)
The books SAY that all regular silver toners can be used on VDB, though
the several I've tried had little visible effect. Palladium toner made
kallitype blacker, so might do same for VDB. That, as well as gold toner &
selenium toner, would improve archivality for sure.
I'm not going to make a separate post on this, but somewhere in the last
day or two someone mentioned sizing paper for cyanotype. Don't bother. In
every case I tried -- and I tried just about every size formula in the
books -- for cyanotype plain paper worked at least as well, usually
better. I would add of course that if you're using a hand-made, rather
than a factory paper, you might well need extra size. But be aware that
the worst size for cyanotype is the gelatine size we use for gum -- in
EVERY case it made a worse print.
Judy