[alt-photo] Re: Gum printing: removing the dichromate altogether?

Peter Friedrichsen pfriedrichsen at sympatico.ca
Sat Mar 26 00:11:38 GMT 2011


The bulk of the dichromate will wash out in the soak/rinse but there 
may be traces left behind. The metabisulfite does reduce any residual 
Cr (VI) to Cr (III) which is less toxic. Even if there is residual 
dichromate, it is not stable under high temperatures and will get 
reduced to lower chromium compounds like Cr (III). Having said all of 
that, as good practice I would make sure it is reduced beforehand to 
eliminate any risk whatsoever.

Regarding metabisulfite, I know it eliminates the stain and residual 
dichromate but whether it actually solubilizes the converted chromium 
compound, I do not know; it is a good question.

Glasses are often coloured with chromium and render it green so it is 
often added for wine bottle glass. Because of this effect, you should 
make sure it is gone or you may taint the enamel colour if there is a 
sufficient amount left.

Peter Friedrichsen

At 02:33 AM 03/25/2011, you wrote:
>Hi all,
>A question, in Gum dichromate, and exposing with UV light and then
>washing it, does this remove the dichromate out from the material
>I know with potassium metabisulphite it removes the yellow stain, not
>sure if it actually removes the dichromate?
>An idea was to try using an glass enamel paint, and print on copper.
>Once its done put it in the kiln. Though with the dichromate still
>lingering on the piece, and adding heat to it through the kiln, the
>dichromate fumes is what scares me, I wouldn't want to be anywhere
>near! :)
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