Halacha Yomis - Kashering, oven window OU Kosher Halacha Yomis This column is dedicated in memory of: Rav Chaim Yisroel ben Reb Dov HaLevy Belsky, zt'l Senior OU Kosher Halachic Consultant (1987-2016)

Q. If glass cannot be kashered, how do I kasher the glass window in my oven? A. As we explained previously, there are two reasons given as to why Ashkenazim do not kasher glass. One reason is because we compare glass to cheres (earthenware). The other reason is because we are concerned that one might not kasher glass properly for fear it might crack. This second reason certainly does not apply to the glass windows of ovens which are built to withstand very high temperatures. Magen Avrohom points out that not kashering glass is only a chumra. Bi’dieved (post facto), if one did kasher glass, the food may be eaten. Rav Belsky, zt”l said that if one self-cleans their oven (libun chamur) one need not be machmir that the glass was not kashered, since the glass window does not touch the food. Although libun is not sufficient for kashering cheres, (cheres requires hach’zaras kiv’shonos - returning to the kiln), still for glass which is only a chumra, one can be lenient.