Hello, luckydawg13. I have seen those "hairs"...I call e'm whiskers, on some SAECO moulds. I see your melt temp. is way up there. Are you bottom-pouring, or dipper casting? If using B.P., is nozzle in contact with sprue hole? You could be "pressure casting" and while this certainly looks to be filling cavity..it can also trap air and cause voids. I would try backing off heat..I usually cast around 600-650Deg. and see if that helps. The fact that it doesn't happen all the time rules out lead deposits I think.