Casting with Englehard bars

Do Englehard .999 silver bars have to be alloyed for the casting
process? Or is it OK to melt and cast just the way they are?
Assuming it is OK to cast in .999, am I correct in my thought that
you end up with “fine silver” as opposed to alloying down to .925
which would be SS? Thanks.

Glenn Block
Shardan Jewelry