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Thought for the Day: Reason Not to Use Glazed Pottery on Pesach -- Not Just a Theoretical Concern

I am so excited.  I get to pull an example from physics to explain why learning the tiny details of halacha are so important.  Life is good.

Let's talk about quantum mechanics.  You've probably heard of the uncertainly principle.  For an electron, than means that you can't know it's position better than the size of an atom.  Do get a feel for how big that is, if the nucleus of an atom was blown up to the size of a ping pong ball and put at the top of the Willis Tower, then you would only know that its electrons are somewhere in downtown Chicago.  That's a big deal for the atom.  On the other hand, if you took a real ping pong ball, the uncertainty in it's position is less than the size of the nucleus of an atom; not a big deal, not even measurable.  So who cares if quantum mechanics is the more correct description of nature?  Well... without quantum mechanics, we would predict that that the entire universe would wink out of existence in less than a microsecond in a flash of ultraviolet light.  Quite psychedelic; absolutely worng.

Knowing the tiny details of why halacha goes the way it does can have similarly dramatic effects.  For example, we don't kasher pottery for Peisach use.  Pottery absorbs and you can never get all of the absorbed matter out, so we we have to get new.  What about glazed pottery?  That is, pottery with a thin coating of glass over it?  Normally we say that glass doesn't absorb, but for glazed pottery we are stringent and treat the glass as pottery.  Ipso facto, we don't use our non-Peisach glazed pottery on Peisach.

But why do we treat glazed pottery like pottery?  There are two explanations proposed:

  1. Once the glass is bonded to the earthenware, it takes on the characteristics of earthenware.
  2. Glass as thin as you find on the glaze is actually porous, just as earthenware is.
Now, then; who cares?  Well, if the reason is like (1), then bonding the glass to something that is kasherable would mean that glazed thingy is also kasherable. One the other hand, if the reason (2), then you are stuck.  Who cares?  As it turns out, you really, really care about this.  Porcelain enamel is glass glazed onto steel.  The inside of your oven is lined with that.  Do you like being able to kasher your oven for Peisach?  (If you think that's no big deal, check with your wife.  Let me know how that goes for you when you recover.)  However, even more than that (WHAT? More than the wrath/concern of a Jewish woman before Peisach?!  Yep...): The food industry used porcelain enamel coated reactor vessels all (steel for strength, glass for corrosion resistance and taste neutrality).  The underlying reason, therefore, affects nearly all the processed food you enjoy.  (Ok, so maybe not more than the wrath/concern of a Jewish woman before Peisach, but certainly in the same league.)

As long as were talking about this, there is one more reason the Mishna Brura mentions for this stringency: Bran (husks of wheat kernels) is used in the glazing process.  Even though bran doesn't ferment, that's a problem because either:

    1. Bran is a part of the wheat kernel; so even though it doesn't ferment, the Torah still calls it chameitz
    2. It is a stringency for Pesach because... well... it's Pesach, for crying out loud
As it turns out, there is a process for making alcohol that starts with bran, and alcohol is used all over (not just for drinking), so...

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