[Speedslug]

You might try playing with stained glass pieces.

The Pyrex works out to be Boro or Boro like (coe 33) in its stiffness and needing more heat than the "softer" glasses.

I think stained glass is either coe 90 or 96 and should work a lot faster with less heat and a less intense flare in the flame.

Bottle glass I think runs a little stiffer than stained glass somewhere around coe 82 or 86 but remember that bottle glass won't be consistent from one bottle to the next because it is only made to hold it shape to contain liquid and not made to remelted again.