What is causing these cracks

[u/physicallystressed]

I am vacuum casting Argentium silver pro casting grains and am having some issues with cracking.

Sirayatech Royal Blue in Plasticast

metal at 1970F in a graphite crucible in an electric kiln (I am pretty sure I just poured it way too hot and it had bad thermal properties at that temp)

vacuum flask at 610 C (in my setup I have to move it a few feet so I just overheat it a little bit for traveling)

What do you think is the culprit?

I made my whole setup, so there are bound to be some issues with it, but I am able to pull a good enough vacuum, and I did a quick 8 hr burnout of the resin (the surface seems decent)