Investment powder for vacuum casting

Investment powder for vacuum assisted casting of Efedur???

I’m using Silicone bronze (mostly Evedur). I’m using Kerr Satin Cast
20. I’m using vacuum assisted casting (withperforated flasks). I’m
getting small pitting in my castings.I cast objects up to 1 Kg in
weight. I’m told by the producers of Evedur that the pitting is due
to my habit of pouring at 1950 F and I should be pouring at 2100 to
2200 F. Kerr states that Satin Cast 20 is only good below 2000 F.
And I know from experience that pouring above 2000 F produces a very
rough black surface on the casting. Dropping the pouring temperature
below 2000 F dramatically improved my castings. However I still want
to get past the remaining pitting. I’ve search the net for an
investment powder that will allow the 2100 to 2200 F pouring
temperature AND remain as porous (to allow the vacuum to be of
assistance) as Satin Cast 20. I haven’t found anything. Does anyone
know of this problem andits solution?


Silicon bronze has a melting temperature high enough that it will
cause standard investments to flux (melt) if the section is thick
enough to hold the heat for enough time. So thicker sections will
get that nasty black rough surface. Try Satincast Xtreme it may hold
up a little better at that temperature. But for the best results you
need to move away from gypsum bonded investments. Either high temp
investments for platinum or shell casting.

James Binnion
James Binnion Metal Arts