Good day. I have been following this tread with interest. Some 20
years ago during a remodel of my house, I needed a special
electrical box flange. I had one flange, but needed another. It
was about 4 inches in diameter and � inch thick with various holes
and protrusions. This was prior to becoming hooked on
metalsmithing and jewelry. I had a method of melting aluminum and
had heard of sand casting so I thought I would give it a try.
I took very fine sand and made an impression from the existing
flange, it did not hold detail as nothing bonded the sand. I next
tried wet sand with impressive if not effective results when the
molten metal hit the damp sand!
I next turned to plaster of paris. I molded the part, removed it and
let the plaster of paris dry for a day. When I poured the molted
metal in, I found that it still had a lot of water in the plaster,
and metal again spewed all over. I did the mold again, but this
time I put it in my home oven at 500 degrees F for a couple of
hours, then while it was still hot, I poured the aluminum (melted
beer cans, and scrap metal) into the mold. It worked great! A
little shrinkage as it cooled, but very usable.
Silver melts at a higher temp than aluminum, so it may act
differently, and knowing what I know today, I would not use plaster
of paris when casting mix is so readily available.
Cast metal also has a different grain structure and does not seem to
work as well as metal that is forged or worked.