Thursday, January 26, 2012

Burning your sink?

Last night, during a shiur on common Kashering questions, I was asked about a unique method of kashering a sink. My sense is that this approach does NOT work... but it does sound entertaining.

Normally, we kasher a sink by heating water to a high boil, and then pouring it all over the surfaces of the sink. Some authorities also place a heated stone on surfaces of the sink while pouring the water, because the water cools off between the time it leaves the pot or kettle and the time it strikes the sink's surface. The process is tedious and messy.

So the new method (new to me, anyway) is this: Spread brandy or whiskey over the surfaces of the sink, and light it on fire. Essentially, flambe the sink.

Definitely a guy's way to kasher.

Again, my impression is that this does NOT work, from a kashrut perspective; as I understand it, the heat from this fire is directed outward, and the material beneath the alcohol layer is not heated. [Watch the video I linked on "flambe" above; the crepe certainly doesn't show any sign of singeing. On the other hand, perhaps it does get hot enough to reach the level needed for kashering.]

Have you heard of this? From a reputable source?


  1. For years this was the way we kashered campsites for bnei akiva camp in new zealand. When I was about 14 a new rabbi arrived and told us we could just use boiling water. This certainly took all the fun out of it for us budding pyromaniacs.
    For years, after learning hilchot kashrut, I have wondered whether the flambe method worked, but haven't found a good answer.

  2. My first reaction is that you could do both - pour boiling water in the sink and drink the brandy. :-)
    But seriously, the flambe method must be meant to be like libun. I would think that is would be possbile to attach sensors and measure how hot the sink gets during the flambe.

  3. This occurred to me as a material engineer:

    Are some modern sink materials (alloys or ceramics) less porous than past materials, so much so that less extreme kashering methods would suffice? What type of physical or chemical testing of a given material or finished part could demonstrate this to a tech-savvy kashrut posek's satisfaction?

  4. Don't forget to clean the sink first (before either method).

  5. For stone countertops, there's another method besides the dangerous pouring of boiling water on the (clean) surfaces: spray with water and iron with an electric iron. Hear the water sizzle.

    I believe this "works".

  6. Our late rabbi in Ramat Magshimim, who was very respected in the Rabanut Rashit kashrut division and was the rav who supervised all of Tnuva until his untimely death was very clear about this as many people used to kasher their counters and sinks (for Pesach) by lighting 100% alcohol and letting the fire 'do it'. He said that it did not get hot enough. He did suggest that instead using an electric kettle (possibly with a long cord or on an extension cord)so that the water is violently boiling while being poured.
    FWIW :)

  7. I remembered after I posted my comment that a friend is a Professor of Engineering and has done research on heat and fire. Here is what he wrote to me:

    Hi Shlomo:

    Unfortunately, this will not work as the surface temperature will be controlled by the boiling point of the ethanol which is quite low ~ 78C. Water boils at 100C so you will not reach the temperature of boiling water.

  8. The real guys way to kasher is the way I kasher our smooth flat-top stove for Pesach. No sissy-like covering with foil - I use a Blow Torch on it!

    When I first asked a shaileh about it, I was told that certainly this is the best way (after scrupulous cleaning), but it's not advised since it will crack the surface.

    But the trick is to keep the flame moving constantly umtil it reaches the right temperature (glows) and not leave the flame in one spot too long or thermal stresses will crack it.

    But I use the boiling water for the sinks. A blow torch would probably leave burn marks on stainless steel.

  9. Rabbi Sedley-
    Interesting to hear it was actually done somewhere... but see the response from Shlomo's friend below.

    Yes, I think they believe they are doing libun, but I don't see it. And now, thanks to your friend's explanation, I have evidence to back up my not seeing it.

    This is a very good question; it comes up a lot regarding glass, pyrex and variations thereon. Unfortunately, the answer is unclear, because of the possible bifurcation of halachic reality and physical reality.

    I've heard of the iron for counters, but how would you handle the contours of a sink? {Note: Stone may present its own complications, depending on the type of surface.}

    Yes, I've done that electric kettle route when needed. Sometimes the stove is just too far away.

    Michael M-
    Cool, but what about the concern that one might not do it as thoroughly as necessary?

  10. Wouldn't this be like the classic pyromaniac technique of spraying one's hands with deodorant and then "holding" a fire? One can do it precisely because the fire burns only the deodorant layer and not the skin beneath.

    (Yes, I spent many years in sleepaway camp.)

  11. This is an interesting idea, but there's also the other side to this, i.e. those who hold sinks don't need kashering at all because hot foods from the fire do not come into contact with it:

  12. This is a very good question; it comes up a lot regarding glass, pyrex and variations thereon. Unfortunately, the answer is unclear, because of the possible bifurcation of halachic reality and physical reality.
    r h schachter has said all the rabbis should get together and "change" the halacha re: stainless steel.
    btw the halachic reality ? would cut the other way here imho - one might say fire is fire.
    Joel Rich

  13. I suspect what we now know chemically about glass influences many Ashkenazic rabbonim to be as lenient as possible about it. E.g. R' Heinemann shlit'a holds in theory you only need one set of glass plates if strictly kli sheni.

    R' Joel -- sorry I don't buy it. Other definitions are "ma'aleh abaabu'os", which is 212 (okay they talk about high altitudes), or "burning straw", or "making the metal glow." Burning alcohol doesn't get any of those.

  14. My father used to blowtorch our stainless steel sinks for Pesach when I was growing up.

  15. out of town but not out of theloopJanuary 29, 2012 at 5:26 PM

    A reputable caterer with a national hashgacha, when he caters at our shul, has to kasher because ou kitchen is not under any hashgacha. I saw him putting a sterno fuel cylinder in our large stainless steel sink and covering the sink with foil. I asked, why are you doing that? He said "Rabbi X" (of this hashgacha) "told me I can do this. It gets very hot." I replied that I'm sure it's hot but it's not a libun, and without libun gamur, kibolo kach polto, you're not being maflit anything. Just use boiling water.
    I honestly think he had no doubt that it was Kosher but had to do something because of the industry procedures.

  16. TRH replied: Cool, but what about the concern that one might not do it as thoroughly as necessary?

    To make sure I cover every area of the stove with the blow torch, I go over it carefully going horizontally back and forth across the entire surace in lines about 1/4 inch high, and then redo it again from the side (90 degrees to the first set of lines). And then a general secondary going over! And I do everything slowly enough to get the surface to glow red. If I see bright sparks, it means that some residue was left from the cleaning so I stay on that spot until the residue is gone.

    Definitely not the fastest, easiest way to do it, but my wife prefers using the original cook top. And also I hear that covering in foil could damage the surface.

  17. Joseph-
    Interesting, but the problem is still one of irui kli rishon when boiling food is poured directly into it.


    Out of town-
    Note: If it were to the level of hagalah, it would work even though well short of libun.

  18. When cost is no object and the item to be kashered is really REALLY heat resistant, this can make impurities vanish:

  19. out of town but not out of the loopJanuary 30, 2012 at 11:47 PM

    If it were to the level of hagalah, it would work even though well short of libun.
    Pleas explain. I don't understand - we have beliyah of bishul (wet), beliya of dry.
    Kebolo kach polto tells us we must use the pelita similar to the rov tashmisho of the kli. Libun gamur works to kasher anything. But How can a libun kal work for beliya bebishul? The plita is not the same as the bliyah?

  20. out of town-
    For absorption via immersion in hot liquid, hagalah - a high boil - suffices to remove taste. That's k'bol'o kach polto, and it's what works for a sink.

    Libun kal is for cases where hagalah should be sufficient, but is impractical - such as for items which cannot be cleaned well.

    Libun gamur (aka libun chamur) is for cases which require bona fide burning, because the absorption occurred via flame itself.