laboratory glassware is Pyrex, Bomex or similar heat resistant glass,
none of them should ever be in direct contact with a flame. The only
exception is a Test Tube and even that should be kept moving in &
out of the flame. The proper way to heat materials in laboratory
glassware (when using an open flame) is to place a Ceramic Center Wire
Gauze between the flame and glassware.
Ours is an extra stout wire
gauze with a fireproof ceramic center. The sides are turned in so no
sharp edges protrude.
Recommended for all glassware.