Recently, a beginning student said to me that they were taught by another jewelry instructor that boric acid powder in alcohol used as a flux was toxic to use. That when lit it off-gassed toxic chemicals.
Has other posters have mentioned, the devil is in the details…
All alcohols are not created equally, and if the person uses
denatured alcohol which was denatured with some of the nastier
denaturing agents permitted (Suggested??) see
http://tinyurl.com/23zs2gv for the EU here is a less official source
EU2
So has you can see the actual composition is somewhat of a
crapshoot, and since some of the denaturants
If the person uses methanol AKA wood alcohol then they are in for a
world of pain as this is quite toxic when evaporated. Isopropyl
alcohol is somewhere in-between
And if you want a real world of pain (for soldering at least) in the
US the BATF has also authorized the sale of denatured rum as
denatured alcohol, imagine the fun of the denaturing agents plus the
residual sugar from the rum production bubbling into a nice
carbonized mess on your solder joint.
Best to do has Jim (and other posters)
has suggested and just buy high proof drinking alcohol (although why
someone would buy 90 -95% pure alcohol to drink (the rest is water)
is beyond me)
See also