Back in the old days of printed circuit board manufacturing, the photoresists
used to define the circuit pattern were all solvent based, rather than aqueous
based. We developed the unexposed resist with organic chlorinated solvents
like "tricky" (111 trichlor); when reworking you would take a bristle brush and
a tray and soak and scrub the panels. Unfortunatly the butyl gloves wouldn't
hold up to the tricky and would grow to about 2 feet long! and fall off. So
you'd never use gloves with the stuff.
Found out eventually that this stuff goes straight to your liver. Sometimes
ignorance really is bliss!
Something even worse: when multilayer circuits boards came along (instead of
just 1- or 2-sided ones) it was necessary to remove resin smeared over the
copper internal connections in the holes. We used to use 9 parts concentrated
sulfuric acid + 1 part concentrated hydrofluoric acid to remove the resin smear
and to "etch" the exposed glass in the holes! We called it "tiger juice"
'cause when you'd get it on your skin the sulfuric would burn holes in it and
the hydrofluoric would eat down through the flesh. It's awfully hard to
neutralize, and flushing it with water makes it even worse. (Kids - don't try
this at home. Hydrofluoric acid will actually remove the calcium from your
bones. I understand there are some extremely unpleasant injections they make
directly to/into the bones to counteract the effect).
Ah, the good old days.
Fred Johnson
Frosty Wisconsin
'69 2000
>>> Marc Tyler <mtyler@hctc.net> 09/25/00 05:46PM >>>
Thomas Walter wrote
>I used to be able to buy Toulene in a 5 gallon drum, industrial
>cleaning fluid. It is also a nice octane booster.
It is also useful as a liver remover . Had the dubious honor of working
with some nasty solvents. Trichloroflourethane,111, now banned is
particularly nasty. I was told by my employer that it was "safety
solvent, safe to bathe in"
-Marc T.
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