Matzos

The flour from which matzos are made may be exposed to water for no more than 18 minutes if they are to be kosher for Passover. Biblical teachings dictate that the dough must be allowed to rise for no longer than the time it took to walk a Roman mile, which has been timed as taking between 18 and 24 minutes. The number 18 is portentous, as it represents chai, the Hebrew for life.

Schmurah matzo is a hand-made matzo that some very observant Jews insist upon eating at Pesach. Bakers gather around the table while the oven is readied. A stopwatch is pressed and any matzo that is not ready in time is rejected and thrown away. Automated, assembly line baking produces matzos much more quickly, usually in about 7 minutes.