Pyrex

Answer

Answered by Chaim Yisrael Abadi

Question: Glazed ceramics, like, for example, modern fine china, effectively have a glass covering. Can they be treated as glass? Yes Food does not penetrate the glazing into the ceramic unless the glazing is poorly done, or somehow rubbed off. Correct Regarding various kashruth boards that argue Pyrex is made of different elements than glass, ... It is not difficult to design an experiment to determine whether Pyrex is pourous like metal or nonpourous like glass. (Glass is also somewhat pourous, just much less so than metal or ceramics). There are indices of porosity. Instead of going round and round would it not be a good idea to simply run such an experiment, publish the results, and settle the issue? In fact, I'll bet Corning has such experimental data already. Question: Glazed ceramics, like, for example, modern fine china, effectively have a glass covering. Can they be treated as glass? Food does not penetrate the glazing into the ceramic unless the glazing is poorly done, or somehow rubbed off. Our modern equivalent of old ceramic (=kele heres) are those certain floor tiles and certain craftsman made pitchers, cups and plates where the glazing is intentionally left off. Correct CYA