Here’s the recommended procedure from PMR for casting stones in
SRS STONECAST R & R SOLITARE
Recommends 2 to 3 hour set up time. Recommends 2 hour set up time.
Steam De-wax - ? to 1 hour Steam De-wax - Optional
356 deg. F - 3 hours 302 deg. F - 4 hours
428 deg. F - 3 hours 707 deg. F - 2 hours
707 deg. F - 3 hours 1247 deg. F - 3 hours
1022 deg. F - 2 hours Cast Temp. - 3 hours
1166 deg. F - 6 to 9 hours Burn out temperature can vary depending
Are you mixing the correct proportions of investment to water? Are
you letting it sit long enough before putting it into the oven? Are
you using a slow enough burn out?
It may help to leave some room under the flask to allow more oxygen
to enter the flask to promote full burn out. Leaving the oven door
slightly open may help as well.
Are you using a gas oven? That might be a problem.
You may be getting ash residue. I haven’t tried casting Viper resin.
I’ll ask around if you don’t get further help with this particular.
Hope this helps