If a utensil can't become meat or milk through bliya, (like wood does) then is it ever possible to become non-kosher?

  • Now glass, according to Sefardim, never absorbs. Clean it thoroughly and you're done.
    – Shalom
    Mar 5, 2014 at 5:30
  • @Shalom That sounds like an answer: if a material doesn't absorb then it can't become non-kosher. Anything beyond that is just science not Halakha. If you could source this principle that would be great.
    – Double AA
    Feb 1, 2017 at 16:45
  • 1
    Wood can't become meat or milk through bliya? Are you sure? Source? Feb 2, 2017 at 9:26
  • Scientifically it's not possible for wood to absorb flavoring because of the material. It could be thought as electrons passing through a metal object, however they can't pass through a wooden one. Feb 17, 2017 at 12:16

1 Answer 1


Indeed a utensil that doesn't absorb cannot become non-kosher.

Glass, according to Sefaradim, doesn't absorb and, if clean, can be used for meat and dairy. As such it cannot become non-kosher (SA OC 451:26, see also for instance here).

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. [...] According to the Sephardic custom, however, a thorough washing is sufficient, as we have explained.

However Ashkenazim consider that glass absorbs and has a status of Kli Cheres, which is to say that glass dishes are equal to that of pottery (which can become non-kosher, see e.g., here).

Your question mentions wood, but wood absorbs and is kashered through hagala (SA OC 451:8).

  • Are you suggesting that glass is a Machlokes in Metziut?
    – Double AA
    Sep 23, 2018 at 12:22

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