fibreglass in plaster moulds

[Ione Thorkelsson]

I have been using fibreglass in the second layer of my mould as recommended by Helen Stokes. This works well to prevent cracking but I wonder if I can make a thinner mould with borosilicate fibreglass or refrasil cloth. Do either of these add strength to the mould? Is there a Canadian supplier or a U. S. supplier who will ship to Canada?