A quick gl-working question?

You ever seen those people who sit behind a blowtorch-like flame and melt thin rods of gl into different shapes? That's what I want to try with my propane blowtorch. (And I know it requires experience, but what I want to do is simple anyway.) For those of you who know something on this subject, how can they melt those thin rods without the rods shattering from the uneven heating? Is it a special type of gl?