Can NOT get my silver molds hot enough

[BurningKrome]

Hi Thanks for the comments.

So, for clarification, I am using a silver investment for casting (Stonecast). Its a Silicon Dioxide (SiO2) "plaster"...but its not really plaster. Should I be using a different brand?

@Josef1: Just small rings right now. But not rings that can be sand cast because the are too asymmetrical. But one of the problems seems to be; with the silver investment plaster I'm using, I can't seem to get the interior cavity above about 250 °C ... even using a 700°C flame blasting into it for 10 mins. The thermal conductivity on SiO2 (the investment) is really low (like 0.02) so it doesn't want to absorb the heat.

I haven't monitored the temperature of the silver while melting, but maybe I should. Do I need to perhaps make the silver hotter?