@aeva showed some work she did on samples that @apix sent her.
I think it was boro, @apix can you confirm?
Obviously not blown or heated post engraving, but still interesting.
I have played around a bit with slumping and fusing soda-lime glass in my little enameling kiln, and I can say that if you are not careful it is easy to trap bubbles between layers. That makes me think that you could use this to good effect by engraving and then layering so that the engraving remained as a bubble trail