Good question.

HXTAL is made to not come apart very easily and it definitely lives up to its reputation.

Probably the easiest way to get rid of a wayward HXTAL bond is to re-anneal the entire piece. The high temperature of annealing will burn off the glue and leave a black residue that can be polished off the glass (it will stink up your entire shop too).

If that's not an option, then you can also try the ATTACK epoxy solvent and be prepared to have a lot of patience. The ATTACK will dissolve the joint, but on HXTAL it takes a very long time and it will stain your piece (a lovely purple shade) so you'll have to do some polish clean up afterwards.