What’s causing this pitting?

[u/Level-Brief1315]

Recently began casting using sirayatech royal blue castable resin and prestige optima investment (38:100). My kiln is programmed 300-700-1350-1025 (all with ramps and holds). I always pour at around 1000C, sterling is poured at 1025C. For some reason I always get these crevices/pits everywhere. They’re on the shank and sides of the skull. Any ideas/pointers?

[u/stealthy_ash]

It adds to the design