Re: A few gum things
From: "Christina Z. Anderson" <zphoto@montana.net> Subject: Re: A few gum things Date: Sun, 06 Apr 2008 21:16:22 -0600 > I can also locate my notes from Ryuji but he may chime in > without my having to do that. Well, I had enough on the first three rounds of glutaraldehyde flame wars, so I didn't have desire to join this round, but thanks for remembering and re-posting my posts. > "Whence, it seems from the LD50 (lethal dose, 50% rat population) values, > that glutaraldehyde is about six times more toxic than formaldehyde *on a > weight basis*. This is generally born out by the recommended Occupational > Exposure Limits, which is about four times lower for glutaraldehyde - again, > on a weight basis. [good stuff omitted...] > What I'm saying is: > > 1) The higher intrinsic toxicity of glutaraldehyde should not be an argument > for preferring formaldehyde, because you are likely to inhale much more > formaldehyde than glutaraldehyde - so the toxic effect is comparable or > worse. > > 2) Both substances are toxic enough, in concentrated solution, to require > handling in a fume hood with an adequate air extract system." Who wrote this? It says exactly what I would say, but the absence of grammartical errors make me think this isn't my past writing (even those I wrote without glasses of Malbec, Rhum Barbancourt or rye whiskey would contain some of my signature errors). Maybe this is the Mike Ware quote? If anyone wants to use glut for teaching purposes, I suggest to use more dilute 0.5% stock and use 5x the volume to match the glut content. Since the amount of glut necessary for optimal hardening is so small, 0.5% stock doesn't impose any inconvenience, and it further reduces the risk of accidental exposure. I would only use this extra safety margin as a bonus, and wouldn't give up usual lab safety precautions. Another thing you can do is to keep the glut stock refrigerated. The most likely occasion for vapor inhalation is when you are adding the glut to the gelatin solution. If the glut is chilled, this vapor is minimized. Once glut is mixed in the gelatin solution, the majority of glut is soon permanently bound to the gelatin molecule and won't vaporize. However, a small fraction of glut will vaporize. I would ventilate the room just to keep the exposure level to an absolute minimum. The beauty of glut hardening is that the paper is ready to use as soon as it dries, and I can also keep the sized paper for a long time without any further treatment. I'm efficiency oriented and I'd rather spend hours of research to prefect each step than having to do extra steps each time I do something. The best of all, glut is sold in a bottle and it is inexpensive. If you don't limit to stuff you can buy, there are many other useful hardeners: bis(vinylsulfonyl)methane, bis(vinylsulfonylmethyl)ether, 1,3-vinylsulphonyl-2-propanol, 2,4-dichloro-6-hydroxy-s-triazine, etc. These are nonvolatile, but in my experience, glut is still easier to use for immediate and reliable hardening reaction in b&w and non-silver-gelatin applications. -- Ryuji Suzuki "The truth that I am seeking is in your missing file." (Bob Dylan, Something's Burning Baby, 1985)
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