Re: clearing dichromate stain
On Dec 12, 2006, at 3:11 AM, Clay wrote: FWIW, the reason that the sodium or potassium bisulfite works is that it is acidic. Sodium sulfite alone is slightly basic, and will not reduce the chromium ion, which is what you are trying to do.Why did it work for me, if it can't work? It took longer to clear, but it did clear. I had used dichromated unpigmented gum and set it out in the sun until the gum was dark brown, so it had a deep stain to clear, and it cleared it except, as I said, for a very slight grey residual, so light I'm sure it wouldn't affect any pigment color. I agree that the bisulfite and metabisulfite is best, but since he could get sulfite right away, and couldn't get the more efficient stuff right away, I thought he'd like to know that I had found that sulfite would work if you leave it a while. Katharine
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