Well, there would have been no harm at all in option #1, which was
the most conservative of your options in many ways. There are times
that we've actually run flasks through multiple burnouts on purpose,
if the item being burned out was a "dense" organic, for example, or
had a high plastic content. It doesn't hurt the investment or
decrease the reliability of the casting to do so.
I've not tried to hold flasks for multiple days at a particular
temp. While I suspect you could do it, the electric bill would be
Finally, your third option has a lot of variables in it. In
open-crucible melting, you need to be suRe:
the metal is clean and well-fluxed with borax,
has reached a really good flow temp without overheating,
is poured steadily and quickly enough that it isn't freezing along
is being poured into a flask whose temp is high enough to prevent
premature freezing (900 F)
has enough force, either through vacuum or centrifuge, to vent the
air trapped in the casting area through the plaster and encourage the
metal to flow into all the spaces of the casting.
In a vacuum caster, that's why you're using perforated flasks. If
you're trying to achieve the same thing with a solid flask in a
vacuum chamber, your results are likely to be inconsistent and not as
good as with perf flasks.
I hope this helps! It's based on my experience, but others may have
different opinions based on the specific equipment you're using.
All I can say is "i hate it when that happens"!
No Limitations Designs