I used to use Satin cast 20 25 years ago and had the same problems
you are having. When the investment was new out of the container that
it was shiped in they seemed to cast moderatley good I then swiched to
Ultra cast and if the investment was over 6 monthe old I had the same
trouble.The heavy particles of the investment sank setteled to the
bottom of the container. That was what was causing the problem. I
then started to using my Scot Murry 12 lb tumbler to mis the
investment for at least a hour before using. I got a three gallon
plastic container with a lid from Gilleanios resturant and I attached
three pieces of aluminun at 120* apart inside . They were about 2"
wide and 7 to 8' long.
I bolted them inside of the container withlid and it seemed to solve
the proble. Since I have switched to Ramson and Randolf investment and
I still tumble the investment for 1 to 2 hours before using and my
results have been 95% better. Hope this will help you.
Youra : Billy S.