We have finished Klal 14, and we discuss a few points not mentioned in the Chayei Adam.
The first point is about schita in regards to hair. The Gemara says that it is assur to squeeze hair on Shabbos due to the issue of schita. We have learned that hair is not halachically considered an absorbing liquid, but rather it traps liquid between itself. Since it does not actually absorb the liquid, it is only schita derabanan. Furthermore, we have discussed that the melacha of dosh mideoraysa does not apply when the liquid is being discarded. We learned that it is a machlokes rishonim whether it is considered a melacha she’eina tzricha legufa and assur miderabanan, or not assur at all. Regarding hair, the Gemara clearly states it is assur, and it is clear that the liquid is being discarded. Therefore, this case would seem to support the rishonim who hold it is a melacha she’eina tzricha legufa and assur miderabanan.
There are actually two issurei derabanan in question when it comes to hair. One is that the water is trapped and not absorbed, and the second is that the water is being discarded. One leniency which this accomplishes is that when it comes to a davar she’eino miskavein (when a person does one muttar action but we are concerned a second, unintentional, assur action will occur as a result), even if it is a psik reisha, if the person has no interest in the result, it is not assur. (Psik reisha d’lo nicha lei in a double derabannon is Muttar, Mishnah Brurah Siman 316)
The issues of squeezing only apply to parts of the body where there is a significant amount of hair within which water could be trapped. If there is not enough hair, it is not even assur miderabanan.
Thus, over here, if a person is involved in a muttar action–such as drying oneself in an area of the body which is not hairy–and they end up drying a part of the body which is hairy, if they do not care for the outcome (psik reisha d’lo nicha lei), it will be muttar. One practical application of this halacha is a man drying his face. Even though there is no issue of schita on the face, there is an issue of schita on a bead. Nevertheless, as long as the man does not have interest in the result, it will be muttar to dry one’s face. (Another suggestion would be to drape a towel over one’s head, as long as they do not press down.)
A question which comes up regards squeezing sweat from one’s hair. It will not be deoraysa, since hair does not absorb liquid. Additionally, the sweat is discarded. Nevertheless, it should be assur miderabanan. Rabbi Falk points out that Chazal assur squeezing a liquid which is sometimes used to not use it, since it may lead a person to squeeze out the liquid to use it . This is the reason that water cannot be squeezed, even if a person has in mind to discard it. However, sweat is not used for any purpose, so Rav Falk argues that Chazal never extended their gezeira to a case of squeezing out sweat. Therefore, he holds it should be muttar to squeeze sweat out of one’s hair.
Summary
Although hair does not absorb liquid, but rather traps it, and the liquid squeezed will be discarded, it is assur mideraban to squeeze hair on Shabbos.
Due to the double derabanan, a psik reisha d’lo nicha lei will be muttar
It is muttar to squeeze sweat from one’s hair.
