> 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.
No no, it wasn't the dichromate in the cyanotype I meant. It was the
dichromate in GUM dichromate. I'm only testing with cyanotype for an easy
& relevant comparison of fluorescent bulb types, and any negatives ruined
there would be mere three-dollar 21-steps. These were *real negatives*
that apparently soaked up some dichromate, creating a brown stain which is
VERY opaque and hardly noticeable -- you don't see it until you see the
white blob on your print & then have to look very sharp to find it -- but
for whatever reason none of the pigment comes with, just that browning of
the silver.
Carson Graves has suggested a sodium sulfite bath or hypoclearing agent,
which I haven't had a moment to try yet, tho I doubt the two that were
cooked in because I *re* exposed them before I caught on will be so easily
disposed of. When I discovered one right after the exposure where it
happened I was able to wash it out simply by swabbing with distilled...
(The moral being to check the negative immediately upon seeing non-image
white blobs in a print.)
> 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.
It does happen on occasion, but less often with the cyanotype and I
speculate (only semi-facetiously) that it's the water over there, or
something. Now it occurs to me that because I do encourage students to
use a smooth hard paper for cyanotype (and use one myself, a Strathmore
one-ply drawing vellum, 1940s vintage) it doesn't absorb as much emulsion
and therefore blobs less. Another thing I think of now is that we almost
always apply cyanotype with a foam applicator which simply doesn't hold as
much emulsion as a brush. (Not that students don't slosh cyanotype, but
their field of choice is walls, cabinets, floor.)
Gum, on the other hand, may be applied very thick (confess I am guilty in
this respect), and also on thicker paper, meaning heavy layers, slower to
dry.
> One solution is to use Judy's favourite grunge rock band, Tween 20 (the
> wetting agent) - it helps the sensitizer into the fibres.
Do you know anyone who has used Tween 20 for gum printing? Guess it might
prevent clearing, but then again.........? Is it like glyacol,aka
dispersal agent, which did prevent clearing? (Is a surfactant a dispersal
agent?)
> 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,
Well, I'm not sure it's broke so may not need to fix it, BUT, isn't
ammonium ferric oxalate one of those chemicals, like the ferric oxalate
used as platinum developer, that's *always* getting old & going bad?
True, my am fe cit was bad, but that was first time in 16 years!
Judy