Hallo, some years ago I was at the university, busy trying to melt glass, but with months of efforts all I got was a single glass bead, made out of the bottom of a beer bottle.
I used a common Bunsen burner like this one:
plus a pair of long thongs to hold the glass and a small iron toothpick-style tool I made to pierce and manipulate the glass.
Melting the glass itself is not really difficult, but what I couldn't do was mixing two different pieces together.
I even tried melting some glass mosaic tiles I found on a Roman archaeological site I worked in, because their glass was supposed to be much more pure than our, but these small squares were all cracked after so long time under the ground, and with a lot of bubbles, so I couldn't do anything with them.