Depends.  Shells are

Stephen Richard

Depends.  Shells are calcium.  Calcium slowly burns off in the kiln.  Thus shells are not permanent moulds.  The calcium has a tendency to stick to the glass, so needs batt washing.

My view – it is better to make a flexible negative mould, from which a positive can be made.  This can be permanent or one use (you do have a master now)

Stephen Richard

blogs at:   and

People Who Like Thisx