There's no reason to use "non-sized" watercolor paper unless you want
the rough soaked-in effect. You can get a good rich cyanotype on
almost every paper, from a brown paper bag, to a coffee filter, to a
government issue post card, not to mention plywood, wallboard and your
cotton Jockey shorts. One of the few papers over the years that tends to
give trouble (white flecks, loss of definition, etc.) with cyanotype is
Rives BFK, tho it is perversely one of the most popular world wide. I
suppose it's exactly that roughness -- it looks arty. It has been reliably
stated (& just as reliably denied) that it is buffered, which is *bad* for
cyanotype, tho I guess you could test this with a pH pencil.
Meanwhile, my opinion, FWIW, is that cyanotype will do an exquisitely
delicate long scale, almost the equal of platinum. Why screw it up with
blotting paper or BFK? Try a hard finish -- a bristol plate, a Strathmore
drawing bristol, fabriano artistico, even a rag-content typing paper (as
long as it's not corrasible bond, which is resin coated & won't absorb
emulsion). Assuming of course that your negative is long-scale continuous
tone & not a high-contrast "lith" effect, in which case you might as well
use the blotting paper.
> So I would like to have suggestions about specifications of a good
> Cyanotype paper (weight, rag content, others). The (test) paper I now use
> can stand water, but the wet image tends to be very vunerable, this is
> standard?
I suspect that the wet image is "vulnerable" because the soft paper
is disintegrating in the water -- like facial tissue.
And how long do you wash a Cyanotype (I guess until the yellow
> color of the unexposed salt is removed), is it possible that the blue
> fades a bit after prolonged washing?
Face down in moving water or agitating, until the yellow is gone -- or a
minimum of 10 minutes for hard paper, at least twice that for soft
absorbent paper. Yes, prolonged washing (say 4 plus hours) can wash out
emulsion, especially if the water is alkaline.
However, an intact cyanotype dries much darker.
Judy