hazards of am di, speed in gum, etc.
This is due, as I understand it, to bureaucracy at work... am di is considered "more hazardous than k di" -- the difference being, apparently, that am di is allegedly a fire hazard, also explosive, hence "hazardous shipping" protocols apply. The am di "volcano" was, it seems, a standard school science fair demo... until the safety police arrived -- but, years ago when this topic appeared on the list, Bob Schramm said the only way to get am di to explode -- or catch fire -- was to put it in a metal pan and smash it with more metal (or words to that effect).If I recall, it is a bigger hassle to obtain am di. More hazardous maybe?Hmmm...I order it by the lb from artcraftchemicals.com and doesn't seem to be a problem tho it is more expensive than pot di if I remember... Chris
Another issue of am di, among the 180 e-mails arrived since day before yesterday (two whole days !) was a comment (maybe from Keith?) about a discrepancy in results from tests with (I think it was) the same neg... My experience has been that time between coating and exposure is a definite variable in gum, especially in hot and/or humid conditions. Which is to say, if two strips are coated at the same time, but one is exposed after the other, that could cause variation visible to the discerning eye.
Finally, re search for shorter gum exposure times... my experience with the Nu Arc was that, as Mark points out, times with closely spaced BL bulbs and Nu-arc were pretty much the same, but most ink-jet printed substrates were noticeably slower than lith film. (My lith film exposures averaged maybe 2 minutes.Paper negs, et al, circa 8 minutes.) However, my BL bulbs were facing up & did at times get a coating of dust, removal of which tended to reduce exposure measurably, tho not hugely.
Also BTW, FWIW, I mention that trying to get shorter/better exposures I replaced the NuArc cover glass with some cockamamie special glass I'm forgetting the name of now --- if exposures were shorter, they weren't noticeably so, and the print quality weirded out, so I put the old glass back.