I was kind've bummed, but I got these two awesome tips from Barry Hall, a ceramic instrument maker and author of the book, "From Mud to Music".
First, clean out the crack with a can of compressed air. For gluing, there are
2 options I would suggest:
1. cyanoacrylate (super glue) - this is really thin and would penetrate probably
better than any other glue. It will be permanent.
2. for a reversible option, use polyvinyl acetate (PVA) aka white glue (like
elmers). You can thin it with water to the right consistency so it will
penetrate the crack. It holds ceramic very well. However, if you want to reverse
it, just soak in water and it will release. It would probably give a more
attractive result because you can wash the excess off the exterior of the
ocarina. The super glue is more difficult (almost impossible) to clean off, and
it's shiny. But you might want to touch up the paint job anyway.
Either way, you want to be sure you completely seal the crack airtight. Might be
difficult with either scenario. You might consider also putting a sealant on the
interior to help seal the crack. This could be diluted white glue. Also
possibly a polyurethane wood sealer. You can also use diluted yellow (wood)
glue, which is also water soluble (but only with hot water). Be aware that
sealing the interior could subtly change the tone, but frankly it might improve
and focus the tone.
The elmer's glue actually worked for me! If you use these two tips, please post your results in the comments to help others who are going through a similar situation.
