We are continuing in siman 5, discussing the halachos of hatmana. The Chayei Adam is discussing a scenario in which a person is trying to perform hatmana on coffee. They dig a hole in the floor of the oven and place the coffee pot there. The Chayei Adam wrote that this is muttar, as we do not look at the oven as mosif hevel.
The Chayei Adam continues, and writes that Chazal understood sand to be mosif hevel. Therefore, if one fills the hole with sand, such that the sand is now the insulating material of the coffee, it is assur to perform the hatmana. Even if the sand is only partially insulating the coffee, and the other part is being insulated with something such as clothing which are only a maamid hevel, it is assur. The Chayei Adam explains that Chazal understood that once a person partially insulates something with a mosif hevel, they were concerned that a person would insulate the entire item in the mosif hevel.
(The Gemara never mentions such a gezeira. We need to understand from where the Chayei Adam got this gezeira.)
Later, in Klal 20, the Chayei Adam discusses bishul. At the end of the Klal, he writes that he neglected to mention something regarding our case of the coffee pot. He writes that if one wishes to perform hatmana on the coffee, they should immerse the pot in the sand, but should not insulate the top with clothing. Then he adds that one should be careful that not more than a half or third of the pot should be insulated, implying that if two thirds or even a half is insulated, it will be a problem of hatmana. He adds to then place a larger pot over the coffee pot, so that the insulating material is not directly touching the coffee pot. This is the same suggestion as placing the board mentioned previously.
This point mentioned by the Chayei Adam, that not more than a half or third of the pot should be insulated, seems to be in direct contradiction to the concept of hatmana b’miktzas which the Chayei Adam previously wrote is muttar. The Mishnah Berurah also quotes this Chayei Adam, even though he also writes elsewhere that hatmana b’miktzas is muttar. This is the source of the controversy about how to deal with crockpots; we will discuss this question further in the next shiur, be’ezras Hashem.
- The Chayei Adam mentions that even hatmana b’miktzas may be assur; we will discuss this contradiction further in upcoming shiurim, be’ezras Hashem.