Re: Gum prints with screen printing sensitizer?
Travis...toggle quoted messageShow quoted text
Tea has more caffeine than coffee does... green tea perhaps...
Andy Schmitt PPA
Head of The New & Improved Photography Dept,
Peters Valley School of Craft
From: Alt-photo-process-list [mailto:alt-photo-process-list-bounces@...] On Behalf Of tdp
Sent: Wednesday, March 19, 2014 9:13 AM
Subject: Re: [Alt-photo] Gum prints with screen printing sensitizer?
Kees! That is extremely useful information, and a link to some wonderful prints as well :) I had no idea that the polysaccharide structure was the problem printing gum with DAS, although no manufacturer in the US will send me DAS so it's kind of a moot point.
One thing to note, I think Greg pointed it out in that APUG megathread, is that there is no free formaldehyde in the ProChem sensitizer, the molecule is either a (here my poor chemistry skills start to hurt) condensate or a precipitate of 4-Diazodiphenylamine and formaldehyde. If there was free formaldehyde it would certainly be classified as a carcinogen here in the states!
I have no doubt that your sources are correct about the toxicity of the screen printing diazo sensitizer. I would certainly not call it non-toxic, the MSDS clearly states that it is toxic by oral ingestion - although it's apparently 10 times safer than caffeine. (Actually, the caffeine MSDS is super scary, maybe I should switch to tea.)
Since wastewater disposal is my first concern, the fact that it isn't ecotoxic makes all the difference between diazo and dichromates. I also don't think it would be wrong to say that this chemistry is substantially less hazardous than dichromates as far as human safety - there's a reason why commercial screen printing moved away from chromium!
On Wed, Mar 19, 2014 at 4:48 AM, Kees Brandenburg
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