quenching in water sounds like a sure-fire way to cause a fire.
You mean, quenching in alcohol…
it does now and then light the alcohol if you quench from too hot,
but it’s actually pretty rare that this happens. The metal should no
longer be glowing at all when you quench. Around 900 F or so, or a
bit less. At that temp, it won’t ignite the alcohol. Also, the
metal at that temp doesn’t actually contact liquid alcohol. It does
the same thing it would do if it were quenched in water. It creates
a layer of vapor around it, and the initial cooling is from the vapor,
not the liquid. Alcohol forms a vapor more easily, and so absorbs
heat in the process more slowly than does water, thus the gentler
quench. When you quench, don’t slowly dip it in. Immerse the piece
all at once. That’s more even cooling than a slow dip. The same
goes for a water quench by the way, or oil. Once the hot piece is
under the liquid, It cannot ignite anything, since there’s no oxygen
there, just the alcohol, and by the time bubbles of the vapor reach
the surface, they’re pretty cool again.
But the main thing is to use a jar, not an open dish. this way, the
access to the liquid, of oxygen/air, is somewhat limited, and more
easily controlled if needed. Alcohol fumes are flammable, but not
especially explosive, at least not in this situation. So when you
accidentally set the jar on fire, it’s a slow gentle simmering flame,
not some sudden catastrophic fire. And the solution is simple
enough. Put the lid on the jar. And don’t get startled into
knocking over the jar!
It’s common practice for goldsmiths to have a jar of a mix of boric
acid and alcohol on their bench for use in fire coating gold and
platinum, especially pieces containing diamonds, which will be heated
or soldered upon. Since in that use there’s usually an open flame
around (one’s torch), the alcohol cup now and then gets set on fire
by the torch too. Same deal. no big problem, so long as you don’t
get startled and drop the jar and spill it’s burning contents all
over… I’ve done that only once, a number of years ago, when for
some reason the jar cracked in half and all the alcohol flowed into
the bench pan to burn. Even then, it’s not a total catastrophe, just
a mess. I laid a wet towel over the burning area, and the fire went
out. simple enough. But I then had to clean up the mess in the
bench pan.
Peter
