I mentioned this last night in the Formula section in the Stars thread but thought I'd ask here too. I can't find any discussion on it but that's because I do not know the term for the phenomenon that is:
A star which during drying, expands and cracks open. Usually in the latter stages of drying.
I have been working on a Sodium Nitrate based composition using fairly coarse MgAl. I used 1% boric acid due to the MgAl and Sodium Nitrate. Not sure what is happening here but obviously a reaction of some kind. Other chems are just Sulphur and Charcoal. Water and dextrin to bind.