Joe Gwinn fired this volley in
:

the other being one part zinc
oxide, one part calcium carbonate, and sufficient water glass (sodium
silicate) to make a slurry.


That's the one, but my understanding was that the zinc oxide is not
active, but only a pigment to whiten up the mix. Of course, I've not
made any in probably four decades, and don't remember if it was necessary
or not.

In any case, ZnO is not toxic, either.

This cement does not dry, but cures, and (IIRC) is waterproof after
curing.

Lloyd