Crack patching Tools, Tips and Techniques Discuss Crack patching in the Pizza Oven Design and Installation forums; I used to use waterglass to attach a new door gasket to my woodstove....just ran across this reference which might ...

[Xabia Jim]

I used to use waterglass to attach a new door gasket to my woodstove....just ran across this reference which might be of interest....

Perlite makes a useful rigid refractory and a mouldable refractory
patching/repair compound using sodium silicate (waterglass) as a binder,
....but it's soft and the bond develops slowly.

[Xabia Jim]

Further thinking makes me wonder if using the gasket material might be good for filling a larger crack that bothered you. (like a smoke escaping crack)

This gasket does remain somewhat flexible to seal the woodstove door. The waterglass keeps it in place.

so this might be a crack filling solution with some flexibility....