We previously discussed the Rabbis understanding of thermodynamics in connection with cooking. The Rabbis understood heat transfer as a function of a vessel in a train of transfers from the vessel originally placed on a fire (or heat source) to cook. We looked at pouring hot water into cold water and cold water into hot water. The Rabbis did not see these as the same process, but came up with different rules based on the receiving receptacle and the ratio of poured substance into receiving substance. Today, we start Chapter Four of Tractate Shabbat and we return to thermodynamics. Only now we look at insulation and what is permitted and what is not permitted on Shabbat.

Many of the rules around cooking were designed to ensure that we did not rake coals (a heat source) on Shabbat because that violated the forbidden labor of kindling. The laws around insulation are designed to ensure that we do not add heat to a dish on Shabbat. We can use substances that maintain heat. Of course, today we understand that we are not adding heat with insulation. We may be trapping heat such that food continues to cook, but we are not physically increasing heat. Any insulation, no matter how efficient, will lose heat over time.

Chapter Four is not very long. We start at the end of today (Page 47) and continue through page 51. Our first Mishnah comes at the end of today’s Daf. We start with a list of materials that the Rabbis believed added heat to a dish and therefore could not be used as an insulating material when Shabbat began. Examples include sand, manure and marc (sesame or olive pulp that remains after pressing the oil). Permitted insulation materials include dry grasses (not wet grasses). The Gemara starts with a discussion of whether marc refers to olive or sesame material, but does not conclude by the end of the page.

Before we get to Chapter Four, we have to conclude Chapter Three. We consider three topics to conclude our discussion of Muktzeh. First, we look at the rules for something that is not Muktzeh itself, but the base to Muktzeh. For instance, a stone is Muktzeh. If I have a basket of fruit, which is not Muktzeh, that has a stone in it, can I move the whole basket? Does the relative size of the stone and the fruit matter for this decision? As part of this discussion, we consider Rebbi who allowed his disciples to move a censer with ashes in it. The ashes were Muktzeh (according to some opinions). Later sages tried to justify Rebbi’s ruling by holding there must have been granules of incense still in the censer with the ashes and those granules would not be Muktzeh. Other Sages dismiss this explanation because Rebbi was so rich, he would not have been concerned with a few granules of incense. We learn that the laws of Muktzeh are somewhat relative to our own personal circumstances.

Second, we discuss whether or not we can re-assemble items on Shabbat. We conclude that much depends on how permanent the re-assembly is. So, reassembling a candelabra violates a biblical prohibition, because we would not expect to assemble and re-assemble it frequently. However, reassembling a plasterer’s pole (which was changed depending on the height of the job), was not subject to a biblical prohibition because we would expect it to be assembled and disassembled frequently. Just to be safe, we do make such re-assembly subject to a Rabbinic prohibition.

Finally, in our last Mishnah of Chapter Three, we learn we can put a vessel under a lamp to catch falling sparks. However, there cannot be water in the vessel, as then we would be extinguishing the sparks.