Re: clearing dichromate stain

[Katharine Thayer <kthayer@pacifier.com>]

On Jan 6, 2007, at 9:38 PM, Judy Seigel wrote:
> I recently had occasion to sort through boxes and drawers of gum  
> prints, probably 100, if not more.  None, NOT ONE, showed  
> dichromate stain, and NONE, not one, had been "cleared" in anything  
> but plain water development.
I think perhaps there are several issues being confused in this  
discussion; I hope Judy won't mind if I tag onto her post in order to  
address these issues.

   First is whether one gets stain or not, which is a function of a  
lot of things operating together:  the paper, the size, the light  
source, the gum, who knows what all.  Some get it, some don't.  I've  
always been careful to say that I don't think that it means that I'm  
a better gum printer than anyone else that I don't ever get stain; I  
suspect that it's more that I've just been lucky in my choice of  
equipment and materials.  Many people do get dichromate stain, so I  
think it's important to address the issue.  Here's my current page on  
the subject if anyone's interested:

http://www.pacifier.com/~kthayer/html/dichstain.html

Second is whether the clearing step is necessary, even if dichromate  
stain isn't visibly present.  I think we've pretty much decided here  
that you only need to clear if there is dichromate stain that sullies  
the colors of the print.  While that's a consensual conclusion,  with  
which I concur (I never clear my prints)  it may or may not not be a  
sound conclusion, since as I've said before, we don't know what  
dichromate stain consists of chemically.  Whether Sil Horowitz is  
right in saying what I assume he meant, that in dichromate stain, the  
dichromate is fully reduced so inert, may be debatable.  If it's  
fully reduced, why does bisulfite, a reducing agent, work to clear  
it?   I think we need more information on the chemical nature of  
dichromate stain before we can answer that question definitively.

Third is whether extended water soak "clears" dichromate stain.  As  
can be seen on my page referenced above, water fades stain to a  
lighter brown, but doesn't actually "clear" it in the same sense that  
bisulfite clears it, with a chemical reaction that changes the nature  
of the material.
Katharine





> I have on a few long-ago occasions used the clearing baths under  
> discussion (except alum), more or less interchangeably, depending  
> on what was at hand. But that was for rare dire conditions