>The B went into the A with no blue precipitate -- all hail Dr. M.
"'Twas nothing," he replied modestly, "the addition of dichromate is, in
truth, a well-known recipe for cyanotype."
>(And OK Mike, since you
>know so much, can I get the dichromate stain out of my negative with a
>drop of this & that?
Doubt it, because the small amount of dichromate is the least of your
problems if you get cyanotype sensitizer on a neg. All that ferric iron is
going to *eat up* the silver. When this happened to me (it's True
Confession time), I was left with holes in the image - nothing left to
redevelop. Let us know if you're luckier.
>When my students blob up their negatives with wet
>emulsion I lecture them on carefulness & say it's a total loss. But now
>it's happened to me! And right in the middle. Of *two* negatives! I'm
>thinking of a bleach & redevelop bichromate "stain remover." Anybody?!)
This does highlight another problem with ammonium ferric citrate as a
sensitizer: it's very deliquescent and the solution doesn't penetrate
cellulose fibres very readily. So there is a real risk of getting moist
blobs on the surface of your cyanotype paper, unless you coat and dry very
carefully.
One solution is to use Judy's favourite grunge rock band, Tween 20 (the
wetting agent) - it helps the sensitizer into the fibres.
A better solution is not to use amfecit at all, but to base the cyanotype
recipe on ammonium ferric oxalate, which is not deliquescent, penetrates
paper better, and prints much faster. See my article in Ag+ Photographic,
vol. 7.
Mike