Re: glyoxal v. formaldehyde
From: "Christina Z. Anderson" <zphoto@montana.net> Subject: Re: glyoxal v. formaldehyde Date: Tue, 08 Apr 2008 08:24:19 -0600 > Thus, when buying the Photographer's Formulary glut you > would need 0.6ml to 2.4ml of the 25%; when buying Maxicide > from a medical supply warehouse which is a 2.5% solution, > you would need 6ml to 24ml of this to your liter of gelatin > made up as a 3%. I usually use 6-10ml of the 2.5% per > liter. 30 ml which I tried one time was absolute overkill. Wow. Do they sell 25% stock of glut? I handle 25% stock myself, but only in fume hood, and only after sleeping 8 hours and drinking my coffee from Yemen or Ethiopia. > Two, the reason glut is so effective, aside from the fact it > does not outgas (it does have an acrid smell when I first > dump it in the thermos of hot gelatin) is the smoothness it > produces. Both formaldehyde and glyoxal make the > gelatin....feel rough. Glut is smooth. Now, I am not a > chemist and have no idea why this is so and can only > describe it in layman's terms, but it feels like a bandaid. I agree. A glut molecule has two sites that can bind with gelatin to crosslink two gelatin molecules, and the distance between those two sites (counted by the number of carbon atoms between them) is very close to ideal. This contribute to the efficient, fast reaction of high yield, and also better control of gelatin swelling (not too much, not too little). Some other hardeners can have the same property, and in fact those vinylsulfone hardeners have the same property and they are widely used, but the compounds themselves are probably synthesized by the photographic film/paper manufacturers or their group companies and not generally available. > I would be the last one to propose using toxic chemicals, > but we are already doing so. Dichromates, formaldehyde, > glyoxal, might even throw in prescription meds in there. > Apparently this era is nicknamed the prescription med era > and there was some news program talking about all those meds > in our water supply!!!! All those meds messing with our > brain chemistry scares the heck out of me. I'll stick to > coffee. Again I agree. I have removed all harmful compounds that can be substituted with safer alternatives without losing performance in my silver gelatin processing solution, and I've also considered energy needed to synthesize ingredients, etc... I also want to optimize the bottle packaging and all possible areas to minimize health risk and environmental impacts. HOWEVER, for those who are committed to hand made photographic prints, I think glut toxicity is a relatively small problem that brings a huge advantage. I wouldn't rate glut "safe" in the general consumer standard, but compared to its alternatives (that are available commercially), I'd say it's safer and better. I said this several times before, but ALL hardeners are dangerous, because they can crosslink protein molecules in the skin, in the eye, etc., just like they crosslink gelatin. I wouldn't waste my time seeking a completely innocuous hardener. Glut keeps for a long time as long as it is kept in an acidic solution (pH of about 4 is good), in a tightly closed container, in a cool, dark place. Not as air-sensitive as developers or formaldehyde or glyoxal, but I'd still avoid air. > However, don't med students get exposed to formaldehyde all > day long with cadavers? Cadavers are fixed with a fixative (which probably blends formaldehyde and glutaraldehyde, among other things, such as some dyes) but the solution in the sprays used to wet the body in everyday dissection is probably just biocides (they can be phenol, thymol or similar componds) and surfactants. The spray I've used smells just like Chloraseptic spray (oral anesthetic spray for sore throat) which contains phenol. By the way, that type of spray doesn't really work well for sore throat beyond 5 seconds, besides, phenol is not something I want to put in my mouth (or the drain). (But at the same time there's nothing really effective you can do to take care of bad sore throat...) -- Ryuji Suzuki "The truth that I am seeking is in your missing file." (Bob Dylan, Something's Burning Baby, 1985)
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