Well you don't say where you are from... But MAPP gas is a brand name of propylene... I have heard other brands have a different formulation that can cause problems. I recommend you turn the torch down.. Til it is almost off... And try again. Also, stay away from the torch oriface, you want to be further out past the inner blue flame. A lot of newbies don't get how much heat and how far away ya need to be to make the glass sing.. And practice, patience and perseverance
keep trying!