As we start the march towards Pesach, let us explore one of the important components in baking the matzos. One main concern is that if the dough warms up, it can become chametz more quickly. Therefore, we try to keep the dough as cool as possible and do our utmost to ensure that the dough does not become chametz.
MAYIM SHELANU
This starts with the water being drawn at a specific time of the day to ascertain that the water is not warmed, and it doesn’t become chametz earlier than eighteen minutes. This is known as mayim shelanu, water that was drawn in the evening and stored overnight.
This is something spelled out in the Gemara in Pesachim and codified in Shulchan Aruch (455:1): The water should not be drawn during the day, when it is warmed by the sun. Furthermore, the water should not be drawn during the nighttime, when the water also gets warmer. Additionally, the water should not be transported under the sun.
THE FLOUR
The flour also has similar regulations. One should not use freshly ground flour, which can still be warm. It is preferable to wait at least 24-48 hours after the grinding to allow enough time for the flour to cool off. This is especially relevant to those who use reichayim shel yad, a hand mill, and are sometimes behind schedule. They should try to finish grinding at least a day or two before they bake the matzos.
Similarly, the Shulchan Aruch (453:7) stresses that one should be vigilant with the sacks of flour that they are not kept in a place that could warm them. This includes not transferring them directly on the body of a donkey, unless there is a saddle or other material to keep away the heat. Similarly, the bags of flour should not be stored on top of each other, thereby warming them.
THE DOUGH
These precautions continue into the next part of the process, when the flour is mixed with the water and is now in danger of becoming chametz. The Shulchan Aruch (459:1) writes that the dough should not be outside or even facing a window that is under the sun. If it is a cloudy day, when the sunrays are spread out, any window can be a problem. The Rama writes that the custom is not to do the matzah baking next to any windows just in case it will be a cloudy day, but the bakers won’t realize it.
The Rama also adds that one should not transport the dough to the oven in an open area, where the sunlight can warm the dough. However, the Be’er Heitev quotes the Teshuvas Harashbah, who reports that the system in the Ramban’s bakery was that they carried the dough through the street to the oven. He did not seem to have the concern that the sunlight would warm the dough.
IN SUMMARY
We do our utmost to ensure that the dough does not become chametz. This starts with the water being drawn at a specific time of the day to ascertain that the water is not warmed, known as mayim shelanu. We do not use freshly ground flour, which can still be warm. The sacks of flour are kept in a cool place. Once the flour is mixed with the water, we keep it away from the sun.
