I've been told to heat my mold forming the ingot prior to its
pour. How hot should the mold be, and how can I heat it and the
crucible at the same time?
This is a bit of a problem, I admit. Here’s what I do. I have a
couple of heat sources. One is a big fluffy short-flame propane burner
on a stand under a tripod arrangement (actually, under a stainless
mesh pad supported by two insulation bricks). This I use to pre-heat
the crucible and mold. The when things get hot enough I put the hot
mold on the nearby tray (catches any spills), the metal in the
crucible, and get the oxy-propane torch out to melt the metal really
quickly. when it’s molten I touch the mold with wax to check it’s
still hot (and to provide a reduced atmosphere inside) and pour soon
after it’s reached the molten state.
Without the stationary gas burner I guess you put the mold near the
crucible and pre-heat the mold with the oxy-assisted torch (get it all
hot, not just parts of it), then heat the metal. The mold being close
by can benefit from some heat from the torch as well.
I made an ingot (well, sort of) from sterling scraps and was
able thin it out, slowly bearing down about 2/1000" at a time
You might be over working the surface. Roll with more effect, I’d
say. Take bigger bites with the rollers. Remember that the inside of
the metal os also annealed, so rolling deep will get it all squished
ad work-hardened together.
How much borax should be added to the scraps?
Always include a good amount of clean scrap, or new metal. If the
’scrap’ is merely offcuts from clean new stg, no solder, shiny metal,
etc, then I’d consider his ‘new’ metal. But if you include stg that
you’ve been practising reticulation on (for example) then I’d say that
was probably full of oxides and not good to include.
B r i a n � A d a m
N E W Z E A L A N D