"Bernd" wrote in message
...

"Jeff Wisnia" wrote in message
...
mkazemi wrote:
If the housing is off the car and you don't mind spending some time, you
can submerge the part with the busted tap in a boiling concentrated
solution of alum. You'll see bubble coming from the tap and in a while
it'll be eaten away, without damaging the aluminum.

Jeff,

What is "alum" and where can you get it? I've seen this mentioned many
times here when somebody breaks a tap in aluminum or non-ferrous metal.

BTW, he must have really wrenched on that tap to break it. IIRC they are
large threads, to a guy who works with small steam engines anyway.

Bernd

"Alum" is old term for Aluminum Potassium Sulfate, used in various
manufacturing processes, not usually found in the house.
"Ammonium Alum" is Aluminum Ammonium Sulfate, the common astringent, that is
what I think the OP means.