I think the issue is that it is too powerful and engraves too deeply. I use 5-10 watts ( from my 35 watt laser ) for glass and anymore blasts the glass away in fragments and if you run your finger over it after you will cut yourself on the shards. I clean it up with steel wool after and this helps. I am still experimenting with different materials and having a fun time trying different things but I would love a 80-100 watt laser for cutting.........so much faster. ULSinc use 2 x 30 watt tubes in their 60 watt machine and stop one of them when engraving but use both of them when cutting.
I am not completely useless.......I can always serve as a BAD example.