Dear Tim: I picked up your thread regarding platinum casting.
Even though I represent a supply company and some of the
"orchids" consider us the enemy, here goes. We introduced “Silica
Z” from Japan about a year ago. Since then, we have produced the
product in the USA as have some other dealers. We still call it
Silica Z, our product # is 16-515. Price is by gallon $45.00 or 5
gallon pail $165.00. It is a non-acid base which cleans the
castings inside of 20 minutes from platinum investment.
Regarding the surface problems you refer to, there are many
differant investments out there for platinum. AstoVest may be the
most difficult to use because the phosporus acid is mixed already
in the investment, “just add water”. The rest of the investments
are binder seperate (and a little more forgiving). The more
expensive the investment, the more consistent the silica
particle size and quality. New investments have come out which
accelerate the drying time (3-10hours). A good absorbant paper
inside the flask also sppeds drying.
However, I am convinced that centrrifugal casting (whether with
melting by torch or induction with double brken arm) will never
produce smooth consistant surfaces. But of course we have an
agenda because we sell a new technology from Japan incorporating
pressure and a slow spinning of the flask. I can send a copy of
the article from Platinum Day this past March that explains this.
Hope to be of help. #:>).RG