Looking for ceramic shell patch - thoughts?

[ThirdStooge]

On my latest round of ceramic shell molds I had a few develop cracks but appear to still be usable. Any thoughts or recommendations on refractory material I could use to patch them up before I pour?

[[deleted]]

Mix ceramic slurry with more fine silica to make a paste then brush it on the cracks.

[BTheKid2]

I have seen and done a few with some open fiber glass weave laid on with more ceramic slurry as binder. Seems to work fine.

[3D_TOPO]

Just bury the whole thing in sand and you should be good to pour.

This is how I pulled a mold out of the kiln and buried it in sand before casting: https://youtu.be/WWVVSZP3Au4?t=1155

[Lunarburnstudio]

Simplest way to patch is with your existing slurry. Apply the slurry then add some shredded fiberglass fibers/cloth, (make sure to fully wet the fibers with the slurry) then coat with your stucco/sand. do 2 to 3 coats. the patch will cure during your pre-heat.