A porcelain crucible was heated to a dull red color, placed on the test material and allowed to cool to ambient temperature.
No blisters, no cracks nor any surface deformations were observed on the worksurface.
A 3/8" Bunsen burner was adjusted to a quiet flame with a 1-1/2" inner blue cone and then overturned on the test material, exposing material to the flame for 5 minutes.
No blisters nor cracks were detected on the exposed worksurface.