Bench Volcanos

Dear Orchideans A rather unnerving thing happened to me today and I
wonder if a similar thing has ever happened to anyone else and
whether any one knows why this may have occurred.

To cut a long story as short as possible, I was in the act of
pouring molten silver into an ingot mold (as I have done countless
times in the past) when there was a sudden and loud bang, the air
above me was full of glowing fragments of molten silver, the
crucible was flying through the air having been blown off it’s
handle and my torch was snuffed out.

Fortunately, apart from a few holes here and there, in bench, chair
and floor, and a little singed hair (I leapt about brushing myself
off) no major damage ensued. The ingot was basically a ragged U

Now I’ve done lousy pours before with holes left in the bottom so I
don’t think it could have been a trapped air bubble popping. I’ve
been working with titanium a fair bit lately and have heard that
titanium dust is explosive, though in this case I only used largish
pieces of scrap silver for melting and in any case, were it
titanium, that would surely have done it’s mischief during the melt.

Any suggestions as to why this may have happened would be greatly
appreciated as it was a rather scary event.

Thanks for any possible answer,
Renate in Adelaide, Australia

Wow, cool Renate! Is there any chance that some of your torch gas
was injected into the mold before the torch was lit? This seems
pretty unlikely to me, but then I have never heard of a bench volcano


Sounds like your mold wasn’t quite toasty enough and/or there was
still some ambient moisture left on it’s surfaces. I pour a lot of
ingots and sometimes if I’m in a rush or my mind is elsewhere the
air, floor and bench will be filled w/ hot little bits of 18k, etc.
I usually am able to follow the wisps of smoke and recover most of
the material, but recovering my pride takes a little longer…


Renate, I experienced something similar many years ago but it
happened in a graduate school sculpture foundry. We were pouring
several hundred pounds of bronze and someone mistakenly brought cold
ingot molds in from outside. They had some condensation on them. In
the rush to pour left over metal into the ingot molds, no one
realized that these were cold molds, with condensation on them. As
soon as metal was poured into the first mold it exploded, filling the
air with tiny pellets of orange glowing bronze. Fortunately there
were only a few minor burns.

I hope that this account provides you with some that
might be of help.

Joel Schwalb

G’day. I was visiting my professional jeweller mate who had a test
tube of gold from the local river. A customer wanted two plain
wedding rings made from it. So he had a rod mould on his bench
waiting to cast a rod ingot, melted the stuff as usual with his
torch, then poured it into the mould. Now I was looking over his
shoulder when the valuable stuff went flying past my ear with a hiss
and a roar - I felt the heat of it as it luckily went past, . He
and I spent a good deal of the rest of the afternoon scraping gold
off the floor, the wall and the ceiling, but we never found it all;
he had weighed what he’d been given first. He (secretly) used a
bit of his own 18 ct gold to make up the loss. His theory was that
the mould had a little water in it. He forgot about telling the
customer that his beautiful rings weren’t entirely Motueka River
Gold, but assured me under oath of secrecy that the local river gold
was only 18 ct anyway; the rest, he said, was silver, copper and a
little platinum. He stamped the rings with his logo and “18ct”.

Cheers for now,
John Burgess; @John_Burgess2 of Mapua, Nelson NZ

If you were using any kind of casting grain which was made by
pouring the molten metal into water. It is possible that some silver
had encapsulated inside of it some moisture. kind of like a kernel of
popcorn. When it gets hot enough the pressure makes it explode.