Halacha for Wednesday 16 Tammuz 5780 July 8 2020

The Laws of Glassware and Pyrex Regarding the Prohibition of Milk and Meat Mixtures-Continued

In the previous Halacha we have written that according to Maran Ha’Shulchan Aruch, glassware does not absorb any flavor from foods placed in it and thus, there is no prohibition to use a glass vessel for meat and then after it is washed well, to use it for dairy (although the Rama does rule stringently that glass shares the same law as pottery; this is indeed the prevalent custom among many Ashkenazi Jews).

Maran Rabbeinu Ovadia Yosef zt”l ruled in his works and Torah lectures in accordance with the opinion of Maran Ha’Shulchan Aruch that glassware does not require Hag’ala and it may be used for both meat and dairy. There were those who challenged the ruling of Maran zt”l by claiming that although Maran Ha’Shulchan Aruch rules that glass does not absorb, nevertheless, the glass produced today is different than the glass that existed in previous generations. They supported this claim with an experiment which showed that a used glass weighed slightly more than a new glass and they claimed that this was a result of the fact that the glass absorbed some of the liquid stored in it in addition to other such proofs that glassware absorbs.

Nevertheless, nothing has really changed, for Rabbeinu Nissim writes that although glassware does absorb, however, since its absorption is much less than other forms of dishes, this is not enough of a reason to prohibit using it for both meat and dairy. Thus, all of the above experiments proving that glass does absorb are meaningless, for the absorption is so miniscule that it is insufficient to create a prohibition.

Maran Rabbeinu Ovadia Yosef zt”l writes that just as it is permissible to use glass dishes for both meat and dairy or for both Chametz and Pesach according to the Sephardic custom, the same leniency applies to dishes made of “Pyrex” which is heat-resistant, for this material is also considered glass and does not absorb. He writes furthermore that even according to the Ashkenazi custom that glassware shares the same law as pottery and cannot be koshered even through Hag’ala, nevertheless, Pyrex and other heat-resistant glassware (such as “Corelle”) may be koshered by means of Hag’ala, for the reason why the Poskim write that glass cannot be koshered through Hag’ala is only because of the concern that one would not perform the koshering process correctly out of fear that vessel will explode because of the intense heat of the boiling water and not because they are like pottery which cannot release the flavor it has absorbed through Hag’ala. However, there is no such concern regarding heat-resistant glass and even according to the Ashkenazi custom, such dishes may be used for meat and then dairy when Hag’ala is performed in between them. This is indeed the opinion of Hagaon Rabbeinu Yosef Shalom Elyashiv zt”l. The Responsa Tzitz Eliezer rules that there is room for leniency in this regard when Hag’ala is performed three times. According to the Sephardic custom, however, a thorough washing is sufficient, as we have explained.

Ask the Rabbi


8 Halachot Most Popular

Making Toast on a Hotplate on Shabbat

Question: May one place a pita or a slice of bread on a hotplate on Shabbat in order to turn it into hard and crunchy toast? Answer: There are two prohibitions we must discuss with regards to our question of making toast on Shabbat out of bread that was already baked before Shabbat. The first ......

Read Halacha

Sitting on Food Items

Question: Is it correct that one may not sit on top of a box containing food or beverages? Answer: The Gemara in Masechet Berachot (50b) states that it is forbidden to act in a degrading manner towards food. Thus, one may not, for instance, use a piece of cake to wipe up a drink that spilled on t......

Read Halacha

Salting Cucumbers on Shabbat

Question: Is it correct that one may not put salt on cucumbers on Shabbat? Answer: The root of this question lies in the fact that with regards to many Torah laws, we rule that “pickling is tantamount to cooking” meaning that a pickled food is considered like a cooked food. Thus, just......

Read Halacha

Washing Dishes on Shabbat Night and Pouring Water on Dirty Dishes

Question: Upon the conclusion of the Shabbat night meal, may one immediately wash the dishes for the Shabbat day meal or should this only be done during the day closer to the start of the meal? Also, is it permissible to pour water onto soiled dishes (which one no longer needs for Shabbat) so that i......

Read Halacha


Question: May one recite the Amida prayer in front of a curtain (covering the Aron Kodesh) which is adorned with various designs?

Answer: The Rambam writes in one of his responses (Freiman edition, Chapter 20): “It is incorrect to pray in front of garments with designs on them, even if the designs are not protruding. We usually close our eyes when it happens that we must pray in front of a wall or garment adorned with de......

Read Halacha

The Law Regarding a Woman Who Forgets to Recite the Blessings of the Torah

We have explained in the previous Halacha that if one forgets to recites the Blessings of the Torah and only realizes this after one has concluded Shacharit prayers, one may no longer recite these blessings, for one has already fulfilled his obligation with the “Ahavat Olam” blessing rec......

Read Halacha

The Order for Lighting Shabbat and Chanukah Candles

There is a disagreement among the Rishonim as to the order of lighting Shabbat and Chanukah candles on Erev Shabbat Chanukah. The Ba’al Halachot Gedolot (commonly referred to as “Behag”) is of the opinion that Chanukah candles must be lit before Shabbat candles because women cu......

Read Halacha

Washing Dishes Which May Possibly Be Necessary on Shabbat

Question: Is it permissible to wash dishes on Shabbat which do not seem to be necessary on Shabbat but might possibly be? Answer: In the previous Halachot, we have explained the general rule that one may not wash dishes on Shabbat if they are not necessary for the day of Shabbat itself. The sourc......

Read Halacha