Re: Gum Preservatives
On Dec 7, 2006, at 4:56 AM, sam wang wrote: I can't parse this sentence, sorry. You're saying that in your experience, gum that comes already dissolved won't dissolve? That makes no sense to me. Even if you mean that once coated as a film and dried, the unexposed gum won't dissolve, that doesn't make sense to me either. If it was dissolved before it was coated, there's nothing I can see to keep it from dissolving again after it's been dried but not hardened. Perhaps you're suggesting that they used a crosslinking agent for preservative and used too much of it, preventing the gum from crosslinking further when exposed, but that makes no sense to me either; if it was crosslinked that much, I doubt it would be soluble in the emulsion. Or perhaps it's something else about the preservative interferes with the crosslinking of the gum once coated? That last is the only reason that I can come up with that would be plausible, but I've never seen it in all the different commercial gums I've used and tested. I personally don't like the cheap (well, they used to be cheap, but as Judy says they're getting more expensive now) dark lithographers' gums, that are full of particulates of unknown nature which I call gunk, but to my surprise even these print nicely, and the hardened gum (when printed unpigmented) is as clear and clean as gum that started out clear and clean. I do have to admit I've only tried two samples of this type of gum. But it seems to me that gum that won't dissolve wouldn't be useful to printmakers either. And it's odd that if prepared gum won't dissolve, there haven't been more reports of this in the decades that people have been using the stuff for gum printing. This is not to dispute your observation, certainly, but only to say.... I don't understand it. Interesting, how people will throw something out like that and then say "but we won't go there" to discourage any response. Sorry, you already went there, and when you go there, you don't get to say "we won't go there." http://www.pacifier.com/~kthayer/html/Dichromate.html Katharine
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