[Avodah] size of a kezayit

[kennethgmiller at juno.com]

R' Zev Sero wrote:
> One issue may be how to determine the density; how big a
> hole can be ignored?  We know that "sponge bread" is
> measured as it is, but what exactly does that mean? AFAIK
> the accepted explanation is that only microscopic holes
> can be ignored, but any hole that can be seen must be
> deducted from the volume.  The only practical way to do
> this is to squash the bread before measuring its volume.

I'd like to ask WHY the tiny holes can be ignored.

Here are two sources to show that although some kinds of airspace do not count towards the kezayis, other kinds DO count:

Mishnah Brura 487:3 writes: "If there is an airspace (chalal) in the matza, the airspace does not contribute to the shiur kezayis, and he must mash it (to measure it properly - A.M.) But if there is no airspace in the matza, then even if it is soft and spongy (rachah v'asuyah k'sfug) there's no need to mash it."

Mishnah Brura 210:1 (5 lines from the end of pg 242) writes: "If the bread was spongy (pas sufgnin) and puffed up to the point where the air in it was not tangible (ain haavirim shebo nirgashim) then one who eats a kezayis of it as is cannot bench, because truthfully, he has not eaten a kezayis."

Okay, let's put that aside for a moment, and look at something else:

MB 208:48 says that if one makes a food from flour, honey, and spices, only the flour counts towards the kezayis for an Al Hamichya; if one eats exactly a kezayis of it, one should only say a Boray Nefashos, because he did not have a kezayis of flour. He concedes that the popular practice ("nohagin haolam") is to count the other ingredients towards the kezayis, but says that "lechatchila tov lizaher" to make sure that there is a kezayis of flour [for the Al Hamichya].

Rav Moshe Feinstein (in Igros Moshe O"C 1:71) goes further and says that one should not rely on the minhag of saying Al Hamichya on a Kezayis of such a food, nor should one says Boray Nefashos on it, but that one must ("muchrach") eat enough so that there is a kezayis of flour eaten.

Here's my question: If the sugar -- which is dissolved into the mixture, and unidentifiable in the end product -- cannot (or should not) be counted toward the kezayis, how is it possible to count AIR, which is even less tangible than the sugar?

Akiva Miller
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