The best fabric to work with for me was satin brocade. (Both the blue/pink and black/purple are this type of fabric.) It melted at a slower rate, and the edges look cleaner.
I tried some really stiff white satin from an old 80's wedding dress, and it burned so quickly.
This one was my favorite. I made it a headband out of some leftover jersey for it and gave it to a friend for her birthday.
I also tried a plain pink satin that I bought a few years ago. It didn't melt but more of curl and warp. It ended up more rose-like because of this.