The melacha of melaben (literally, whitening, but for our purposes, laundering) can be accomplished in different ways. We will investigate whether using salt this way fits into one of the prohibited types.
Melaben applies to cleaning fabrics but not to removing dirt that is on top of hard surfaces. Whether a certain means of removing filth is permitted can depend on the surface in question. For example, one may pour water over a dirty leather object,[1] whereas this is forbidden in the case of a fabric (even though it permitted to wipe a fabric with a cloth).[2] In discussing this distinction, the gemara[3] explains that regarding a fabric, “soaking it is laundering it.” Since a standard tablecloth falls under the category of fabric, it is forbidden to put water on it when it is soiled.
Removing liquid from a fabric may also be forbidden as laundering. The Rambam[4] states that squeezing water out of a garment is included in the prohibition of laundering. There is disagreement among the Rishonim regarding whether this ruling includes all liquids or only water, which is the liquid normally used in the laundering process.[5]
The permissibility of removal of dirt from a garment by means of shaking it is also a matter of dispute. The gemara[6] says that if one is particular about the cleanliness of a certain garment, it is forbidden to shake it out on Shabbat. Rashi[7] writes that the gemara is discussing shaking off dirt. Tosafot[8] disagrees and argues that shaking off dirt cannot be considered laundering; rather, the reference is to shaking out water from the garment, which makes it considered part of the laundering process. The Rama[9] states that one should try to follow the strict opinion (Rashi).
With this background, let us now consider removing wine by absorbing it with salt.
Absorbing a wine spill with a napkin or even a cloth rag is permitted,[10] on the condition that one is careful to avoid pressing on the tablecloth in a manner that would squeeze some liquid out of it, as well as to avoid squeezing the rag afterward.[11]
In some ways, absorbing the wine with salt seems to be less of a problem, as it reduces the likelihood of squeezing the tablecloth and it is not feasible to squeeze the salt afterward. However, our research indicates that the salt does more than simply absorb surface liquid. In fact, it draws out wine that has already been absorbed in the tablecloth and would not be removed by, say, a paper towel. This is precisely why “home-cleaning” experts say that salt prevents the stain from setting and even removes at least some of it, which is more extensive than just absorbing surface liquid. Indeed, from the context of a halacha in a different realm, we know that salt is put on meat to draw out the blood from beneath its surface. In some ways, the salt acts similarly to water, which stops the dirt from setting and “encourages” some of the dirt to come out,[12] and, as stated above, it is forbidden to pour water on the tablecloth. On the other hand, we have seen that not every action that helps make a fabric cleaner is forbidden.
With a dearth of classical sources on this case or exactly equivalent ones, our halachic intuition is that putting salt on the spill is considered like applying a stain-remover to a fabric and is therefore forbidden. This is in line with Rav Shlomo Zalman Auerbach’s ruling[13] that it is forbidden to put talcum powder on greasy clothes in order to soak up the fat. We concur with that ruling, and, as our case seems quite similar, we would not permit putting salt on the tablecloth on Shabbat to soak up wine. Rather, we recommend soaking up what one can with a rag or a paper towel on Shabbat and treating the tablecloth with cleaners after Shabbat.