As it is, a casual reader is left puzzled (a) about the difference between the materials and (b) by the article's detailed discussion of borosilicate glass. I just visited the article for the first time, and FYI, the discussion of borosilicate and soda-lime glass could do with a brief statement about the relative merits of the two materials. Preceding unsigned comment added by Indolering ( talk I'll edit this when my brain isn't so mushy. It is a brand name for a chemical structure, and Corning is not the only producers of Borosilicate. Pyrex is to Borosilicate as Avian is to H2O. Pyrex is not the only Borosilicate glass Halachic Hammer ( talk) 12:47, 4 April 2014 (UTC) When Rabbi Moshe Heinemann, Rabbinic Administrator of the Star-K hechshur was asked, "Do arcoroc, duralex, pyrex, corelle and crystal have the halachic status of glass?" He responded, "Yes, they do". This raises the question: Does Pyrex have the same halachic status as glass or not? While there is a dispute about this matter, Rabbi Ovadia Yosef, shlita, rules that Pyrex has the same status as glass. Pyrex is glass that is reinforced with other materials. Similarly, it can never be considered "dairy" or "meat," meaning that you can use it alternately for both milk and meat, cleaning it out well between use. According to this, a glass utensil can never become non-kosher. Sephardic Jews follow the ruling of the Shulchan Aruch which states that glass is non-absorbent. (Disclaimer: I am not a rabbi and this is not a psak.) Shalom S. As regular glass isn't suited for cooking in, the question never arose. I have the feeling, though, that it's not the Pyrex per se that renders the cookware not Pareve, but the fact that it's used for cooking (heat exposure increases absorption of taste). For whatever reason, Pyrex is not considered so exempt. metal, porcelain, etc.) are said to absorb the taste of the food cooked in it, and therefore can only be used for one or the other glass traditionally is exempt from this requirement. The question isn't whether Pyrex is kosher or not, but whether it's pareve, meaning it can be used for both dairy and meat. Borosilicate is used for scientific apparatus becuase of its strength an non reactionary to anything. Can someone please explain why that is? Is Pyrex actually more obsorbant than glass and could possibly "spiritually contaminate" foods, or is it simply because Pyrex was just never mentioned in the old Jewish laws? Kent Wang 06:52, (UTC) There is currently a controversy in Jewish circles about the sanctity of using Pyrex instead of glass for the preparation of kosher food.