>Richard,
>I am interested in your technique to remove a stain from a dried but not
>completely cleared print. In my years of traiding Pt/Pd prints, I have
>acquired a couple of questionable clearing. (I will not name the
>photographers because their work is great.) However, I would consider
>additional clearing to prevent them from deteriating further. Of course
>a big question is: is this technique safe for the print ? Anyway, you
>mentioned three posibilities. Please send the suggested formulas for
>working solutions and an outline of your proceedure. Thanx.
Well, it's nothing fancy. With both I start very weak. Try 1 teaspoon per
liter of water, of either the potassium cyanide or the hydrofluoric acid.
If my memory serves me, sodium fluoride works well also and is safer to
handle than the hydfuoric acid. Put the print with clearing agent in Waring
blender and blend on high for 5 minutes. Stains will go away, so will
print. (Sorry, I couldn't help myself.) Just clear in normnal manner with
light rocking of tray. There is probably not much need to go stronger than
1 teaspoon per liter, as if this doesn't work there is not much hope, but
you should try stronger before giving up.
All of these may do some damage to the paper but it should be minimal, not
more than HCl does and I've seen plenty of vintage prints that were in all
likelihood cleared in HCl and the paper is still supple.
WARNING: The hydrofuoric acid is mean nasty stuff. You can get some on you
and not know it. It will migrate through the skin and when it evenutally
gets to the bone, big pain happens and there is not much to do about it but
wait and see how much bone dissolves. HFl has an affinity for calcium so
that is where the action comes in at the bone. HFl is a super powerful iron
solvent. HFl is a powerful solvent for just about everything including
glass. Household bleach is also a good clearing agent but I've seen it
visibly bleach pure pd prints and strip Palladio prints to paper white.
Cyanide speaks for itself and should never be used with acid. I've used
cyanide to strip gold off of gold toned platinum prints. It will release
cyanide gas during the stripping process. Not much, but you can smell it.
I once taught this to a workshop class in California. I was commenting on
the smell, saying that the class should take note and remember the
characteristic odor of cyanide gas. Not getting a response I turned around
and the class was in the garden waving at me from the other side of the
sliding glass door of the studio. All joking aside, it is very dangerous
material and should not be dealt with by anyone not fully trained.
Dick Sullivan