Repairing Green River Formation fossil

[trilobyter]

I have a fossil fish from the Green River formation that I want to glue back together and prepare from one side using an air scribe. What glue do you guys typically use to reattach two sides of a fish? I've heard anything from epoxy to Elmers - but I'm not sure which one is the best. I have PVA beads diluted in acetone which I use to coat the fossils after prep - but can that be used as glue as well (in a more concentrated solution)?

[Ptychodus04]

PVA or Butvar work very well as an adhesive if you have the ability to clamp the pieces of the specimen to keep them in place as the solvent evaporates over the course of a few days. I start by making a solution of 10 parts acetone to 1 part PVA. That usually gets you somewhere around the consistency of honey. It takes a few days to fully dissolve. Then I add a touch more PVA beads to thicken it a bit. Once you can scoop it out with a spatula and it oozes but doesn't drip off, it's the perfect viscosity.

If not, cyanoacrylate, is my next choice. It can be a bit of a pain as it will bond the matrix to the bones but that's relatively easy to remove with an air scribe. Don't use any accelerator as this is likely to turn your specimen green.