With regards to using glass vessels on Pesach that were used year round, The Shulchan Aruch HaRav (Orach Chaim 451:63) says that, for Ashkenazim, if the glass vessel was used multiple times during the year for hot Chametz (or cold liquid that sat there for 24 hours), any hot liquid that was used on Pesach is forbidden to drink, unless the vessel was purged through boiling (Hagalah) or through Milui V'Irrui (filling the vessel with cold water and letting it sit for 24 hours. Repeat 3 times (see here)).

The Mishnah Berurah says the same thing in 451:26:155.

My question is, can one do Hagalah on glass without breaking it? Has anyone done it? Any tricks?

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  • This would only work Bdieved. Why would someone to Hagala on a vessel which he won't be able to use lechatchila anyways? – Shmuel Brin Jan 29 '12 at 4:01
  • @ShmuelBrill, I didn't check the Graz, but the MB seems to say it's l'chat'chila, unless I'm reading it wrong, which wouldn't shock me. – msh210 Jan 29 '12 at 4:24
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    @ShmuelBrill: The Baal HaTanya is Machmir like the Ramah by Pesach. There are many Poskim who hold that what the Ramah wrote was only a Chumrah for Pesach, but for the rest of the year Hagalah would work on glass. See for example The Minchat Yitzchak hebrewbooks.org/pdfpager.aspx?req=1597&st=&pgnum=156 (main point starts paragraph 4): hebrewbooks.org/pdfpager.aspx?req=1597&st=&pgnum=157 \ – Menachem Jan 29 '12 at 4:47
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    @ShmuelBrill: I didn't want to get into it in my question, but the Madrich L'Hachsharat HaMitbach (for the regular year, not Pesach) published by "Mivtzah Kashrut" rules that Glass may be Kashered by Hagalah (for year round use) for this reason, and brings a list of poskim that hold that this may be done, the Minchat Yitzchak was one of them. - I didn't look up the rest. – Menachem Jan 29 '12 at 4:48

I've never tried to do Hagalah on glass, so doing this may very well break the glass, but here's something I thought about:

One thing to remember is that the Halacha, in order to purge something of its non-kosher taste, you only need the same level of heat that caused the vessel to absorb the non-kosher taste in the first place.

Since we're talking about trying to Kosher glass with Hagalah, the vessel probably wasn't used to cook in (in other words, it was never placed directly on the fire). If so, worst case scenario is that boiling, non-kosher liquid was poured directly into the glass container. If so, in order to Kosher it you would only have to do Irui M'Kli Rishon (pouring boiling water from the pot it boiled in) - see here. This could potentially be less problematic than trying to put the glass vessel inside a boiling pot.

Another thought I had (untested) is that if the problem is extreme changes in temperature may cause the glass to break, what about putting the glass vessel out in the sun first, and letting it heat up that way?

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  • or in the over at 200 degrees F which is still below boiling. – Double AA Jan 29 '12 at 17:05
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    And as always, whoever is reading this should consult his rabbi for practical guidance rather than relying on this site therefor. – msh210 Jan 29 '12 at 17:56
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    @msh210: I deliberately did not ask the halachic question, but the practical method of how to do hagalah on glass without breaking it – Menachem Jan 29 '12 at 18:38
  • @Menachem, I know; and this answer is pretty halachic in nature. – msh210 Jan 29 '12 at 18:57

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