The posting from firstname.lastname@example.org was right on. I’ve been casting
for about thirteen years now and have had a recurring problem with
breakouts and cracking. I’ve gotten lots of advice on the subject and
have read several casting manuals looking for a solution. Many
included too much water as the problem but nobody ever mentioned too
Many years ago I met a goldsmith at a Jewelers Convention in
Newfoundland. He said he always mixed by “feel” and said to mix the
investment to the consistency of sour cream. I know now that that
would make the investment short on water. In the last few months I
have been mixing my investment and very carfully measuring the
ingredients. I use a very large injection needle to measure the
water. The result has been perfect castings every time. The mixed
investment has the consistency of whipping cream (unwhipped).
I think that books on casting place too much emphasis on what can go
wrong with your investment. They should simply say measure the
ingrediants exactly to the manufacturer’s specs. and if you have
problems, calibrate your measurement equipment. If you still have
problems, then you can rule out improper mixing of the investment and
look somnewhere else.
Now that I am more confident I have gone back to my investment scale
and use a pyrex beaker for measuring the water. I use the hypodermic
needle to fill exactly between graduations. You cannot imagine the
relief I feel now when I have a half dozen custom waxes cooking and
don’t have to cross my fingers at quenching time.
One of the tips I received from an Orchid member was to harden the
investment by adding Boricx Acid. This helped, but didn’t eliminate
the problem. The draw back was that removing investment from the
castings took quite a bit of time. I still use the Boric Acid but in
much lower douses. It seems to give the castings smoother surfaces. I
use about 3/4 teaspoon per pound of investment.
I hope this saves someone the agony that I have gone through over the