glyoxal "yellowing"
On Mon, 7 Apr 2008, kerik@kerik.com wrote: ... I use glyoxal for workshops because it may be less hazardous than formalin, especially in a group setting. It hardens well, but if the sized paper is not used soon after application, the gelatin will yellow. My tests show that if the paper hardened with glyoxal is rinsed after hardening it doesn't yellow. I found the minimum time of the glyoxal bath by testing -- that is, if you don't harden that long, the rinse will wash off the glyoxal before it's had its effect... I don't remember the time now & think I did that test after P-F was over. I'll check my notes when I have a chance, but 5 minutes for hardening would be more than enough. J.
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