Remember when I suggested you could use birdseed in place of grog in wadding? Yeah, don't do that. Not just because of this creepy terrarium, but also because in the last firing a few of the seeds exploded, sort of like an egg in the microwave, I guess. They didn't do any damage, but any time you've got little bits of debris flying around the kiln you have potential for a bad situation.
I am considering using the chia-wadding, however: the seeds have already split. Will let you know if anything unexpected happens.