Re: clearing dichromate stain
Now that I've had my memory jogged about this, I remember a set of tests that I ran and posted on my site (although I can't seem to find the jpeg now, and fear I may have overwritten it with something else), where I created a dark brown dichromate stain in unpigmented dichromated gum by leaving it out in the sun for a while, then after developing and drying, I cut the stained hardened gum on mylar into strips and treated the strips variously with sodium bisulfite, potassium metabisulfite, sodium sulfite, sodium chloride, and plain water. The sodium chloride, I think, was because someone said that sodium chloride would probably work as well as sodium sulfite. The sulfite and the bisulfites both cleared the stain, meaning that they eliminated the brown stain altogether, leaving just a faint residual grey or blue-grey stain behind, although as I reported earlier, it took longer for the sulfite to work. The sodium chloride and the plain water faded the stain (although I think the water took overnight to do that) but didn't eliminate it, just made it a lighter brown, and the sodium chloride ate big holes in the hardened gum. Hope that's helpful, Katharine On Dec 12, 2006, at 12:18 PM, Judy Seigel wrote: On Tue, 12 Dec 2006, Katharine Thayer wrote: <... I agree that the bisulfite andmetabisulfite 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.Actually plain water will also work if you leave it a while (and I prefer it because the metabisulfites make me choke). But I do remember in the early days of the list, maybe it was Mike Ware (and/ or others) saying sodium sulfite (as in gs clearing bath) would work, & although I'm losing memory even as I write, I remember using it & it worked (tho see my first sentence above).
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