Grinding dish for borax cone

I use a small dish about 15 cm round to grind the borax.

There had been a number of references to a small dish and slate
dishes for grinding borax. From the descriptions given the small
china-ceramic dish, or in melamine ware, used for serving soy sauces
and other chinese condiments would seem to be a suitable utensil for
this purpose. They cost just a few tens of cents in any chinatown
general store.

Kelvin Mok

Melamine will not work as well as expected. The plastic will
contaminate the flux and can (I’m not saying will) cause problems. Tony

Gold and Stone