The Eighteen Minute Matzah Myth

Compared to Judaism’s regular dietary laws, the rules for being Kosher for Passover are decidedly stricter. Not only is the punishment for consuming chametz the more severe karet (Ex. 12:15, 12:19), but the chametz is prohibited even in trace amounts (B. Pesachim 30a). Considering how strict the Jewish community is regarding keeping a kosher kitchen, it should not be surprising to find even more stringencies when it comes to the laws of Passover.

One problem we find with stringencies in Jewish Law is the tendency to confuse the additions with the actual to the point where being confronted with halakhic sources can be jarring to people who might not know any better. I wrote about one such example several years ago, and I recently came across another misconception common enough to be worthy of discussion.

In the newly published Open Orthodox Haggadah, we find the following description of a crucial requirement of baking matzah.

The entire matzah-baking process takes a total of eighteen minutes. From when the flour hits the water, through the kneading, pressing, and rolling, and until the matzah is placed in the oven, we have eighteen minutes. Not a second more (26).

At first glance this should not seem to be a controversial statement. In fact for many of us, this is exactly what we have been taught in school and we can still find similar descriptions scattered throughout Jewish books and websites.

The issue at hand is not so much quantifying 18 minutes as the time in which dough becomes chametz but how these eighteen minutes are calculated. According to the popular opinion cited above, the clock starts as soon as the water hits the flour, from which point we have eighteen minutes to fully bake the dough into matzah.

The only problem is that it’s not quite accurate.

The Gemara in B. Pesachim 48b includes an important quallification regarding how dough becomes chametz

תלמוד בבלי פסחים מח:ב
תנו רבנן: לשה, היא מקטפת וחבירתה לשה תחתיה. מקטפת – היא אופה וחבירתה מקטפת תחתיה, והשלישית לשה. אופה – היא לשה, וחבירתה אופה תחתיה, והשלישית מקטפת, וחוזרת חלילה. כל זמן שעוסקות בבצק אינו בא לידי חימוץ

Our Rabbis taught: Having kneaded [the dough] she forms it [in shape], while her companion kneads in her place; having formed [the dough] she bakes it, and her companion shapes [the dough] in her place, while the third [woman] kneads. [The first] having baked, she kneads [again], and her companion bakes in her place, while the third shapes [her dough]. And thus the round revolves. As long as they are engaged [in working] on the dough, it does not come to fermentation. [Emphasis added]

Maimonides in Hilkhot Hametz Umatza 5:13 adds a bit for effect.

רמב”ם חמץ ומצה ה הלכה יג
כל זמן שאדם עוסק בבצק אפילו כל היום כולו אינו בא לידי חמוץ, ואם הגביה ידו והניחו ושהה הבצק עד שהגיע להשמיע הקול בזמן שאדם מכה בידו עליו כבר החמיץ וישרף מיד, ואם אין קולו נשמע אם שהה כדי שיהלך אדם מיל כבר החמיץ וישרף מיד

As long as a person is busy with the dough, even for the entire day, it will not become chametz. If he lifts up his hand and allows the dough to rest so that [it rises to the extent that] a noise will resound when a person claps it with his hand, it has already become chametz and must be burned immediately. If a noise does not resound and the dough has lain at rest for the time it takes a man to walk a mil, it has become chametz and must be burned immediately.[Emphasis added]

And here’s the Shulhan Aruch O.C. 459:2 for good measure.

שו”ע אורח חיים תנט:ב
לא יניחו העיסה בלא עסק ואפילו רגע אחד. וכל זמן שמתעסקים בו, אפילו כל היום אינו מחמיץ; ואם הניחו בלא עסק שיעור מיל, הוי חמץ. ושיעור מיל הוי רביעית שעה וחלק מעשרים מן השעה.

The dough should not be left without being worked even for a moment, and the entire time the dough is being worked, even over over the entire day, it does not become chametz. And if the dough was left for the amount of time it would take to walk a mil it becomes chametz, and this time is one quarter hour plus a portion of 20 from the hour (i.e. eighteen minutes).

Ramo adds that people are strict to avoid delays in the baking of the matzah, but on the core point there is no disagreement. As long as one is occupied with the dough, the dough does not become chametz. The eighteen minute clock does not begin when the water first contacts the flour, but when the dough is left to rest.

This may seem like a trivial distinction, but it has significant implications for how matzah is made. As anyone with basic cooking or baking experience knows, 1 foods cook more thoroughly when they are heated at a lower temperature for a longer period of time. R. Moshe Tendler – who was fond of saying that the only time people eat chametz gamur on Pesach is when they eat the handmade shmura – frequently insisted that matzot be baked for a little longer at lower temperatures rather than rushing the baking process to meet a non-halakhic deadline and risk the matzot not being fully baked to completion. 2

It should be noted that kashrut agencies tend to be more careful with their explanations. For example, the Stark-K acknowledges that, “the halachah states that chimutz (leavening) does not begin if the dough is constantly being worked,” yet still frames the that time as being part of the hiluch mil calculation.

In a most impressive display of nuance, R. Yaakov Luban and R. Eli Gersten of the Orthodox Union’s kashrut division maintain halakhic precision without challenging popular beliefs.

Chametz is a state that occurs through a process of fermentation. This typically occurs when any one of the five grains are exposed to water and left unattended for eighteen minutes. One can eat raw wheat on Pesach if it was kept dry. Similarly, matzah is not chametz if it is baked within eighteen minutes of the mixing of the flour and water, since fermentation does not take place. [Emphasis added]

Note the two parts of this statement. First the dough becomes chametz only when “left unattended,” yet no one will contest that completely baking the dough within eighteen minutes from the time the water contacted the flour would not be chametz.

At any rate, for those people brave enough to bake their own matzah, keep in mind you may not be as rushed as you think, which I suppose flies in the face of everything else about the Passover season.

I leave the aggadic/spiritual implications of this halakhah as an exercise for the reader.


  1. I.e. Even me.
  2. R. Tendler would often take students to a matzah factory for a personal demonstration of everything which can (and often does) go wrong in the handmade operations. No, I will not be sharing stories.
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