Bava Kamma, Chapter 3, Mishnah 8. We continue discussing how to calculate the amount that may be deducted when returning a deposit given for safekeeping, based on the reasonable assumption that a portion of it will be lost. This Mishnah does not deal with grain, like the previous Mishnah, but rather with liquids - wine and oil.
The difference between wine and oil:
Wine - contains a higher percentage of water than grape juice, and therefore it evaporates.
Oil - does not evaporate at all. The concept of oil throughout the entire Torah refers to olive oil, and the oil that comes out of the olive press has murkiness: it is not clear, and it contains particles and sediment that settle to the bottom of the vessel over time. Therefore, one may deduct what will eventually settle, since it is not fit for use as oil.
A second factor is absorption into the walls of the vessel. With wine, which is stored in earthenware vessels, the wine is absorbed into the walls; and due to evaporation, a continuous process of suction occurs - the wine seeps out through the earthenware wall, and additional wine is absorbed in its place, resulting in continuous loss. With oil, there is no such process, but rather a one-time absorption into the walls of the vessel until it reaches saturation. Based on these distinctions, the Mishnah discusses the method of calculation.
The rate of deduction for wine:
The text of the Mishnah: "Yotzi lo shetus layayin" - for wine, one deducts a sixth of the stored amount, based on the assumption that a sixth will be lost due to evaporation over time (and it does not specify how much time). In contrast: "Rabbi Yehudah omer chomesh" - according to Rabbi Yehudah, the deduction is larger, a fifth, meaning twenty percent and not approximately seventeen percent.
The Gemara explains that there is no dispute here at all, but rather the vessels used in Rabbi Yehudah's locale were different from the vessels in the locale of the Tanna Kamma. Two possibilities are brought as to why more wine was lost there:
The type of earthenware in their locale absorbed more, and consequently more wine was lost.
In the Tanna Kamma's locale, they customarily coated the inside of the jugs with wax to prevent absorption, whereas in Rabbi Yehudah's locale they did not do so.
Either way, the principle is the same: whatever is expected to be lost - may be deducted.
The rate of deduction for oil:
For oil, one deducts for both factors together - absorption into the walls and sediment that settles to the bottom. The text of the Mishnah: "Yotzi lo sheloshes lugin shemen lemeah" - a total deduction of three lugin per hundred, three percent. That is, the depositor handed over a hundred liters of olive oil coming from the olive press, and the watchman returns ninety-seven to him. And the breakdown of the calculation:
"Log umechtza shemarim" - one and a half percent for the dregs and sediment that settle to the bottom of the vessel.
"Log umechtza bela" - one and a half percent that are absorbed into the walls of the vessel.
Since the deduction is merely an expression of the practical reality, the Mishnah continues and qualifies this:
"Im hayah shemen mezukak, eino motzi lo shemarim" - if it was refined oil, he does not deduct dregs. With refined oil that contains no dregs at all, like the oil we have today, one does not deduct the one and a half percent for the dregs.
"Im hayu kankanim yeshanim, eino motzi lo bela" - if they were old pitchers, he does not deduct absorption. When the oil is stored in vessels that do not absorb, such as earthenware vessels that have already been used and are saturated with olive oil, or modern glass vessels, there is no absorption at all and one does not deduct for it.
Thus, if the oil is refined and stored in old pitchers, nothing is deducted.
The Second Part: Purchasing Oil for Ongoing Supply:
The second part of the Mishnah is a direct outcome of what was stated, introducing a new point: a person who enters into a transaction to buy oil. Today, oil is available in the store all year round, but in the time of the Mishnah, there was one harvest a year and one pressing season, and all the oil came out of the olive press only once. The need for ongoing consumption was great - it is estimated that about a quarter of all the calories in the diet of the inhabitants of Judea came from olive oil.
Therefore, someone who wishes to guarantee a regular supply for himself approaches the olive oil producer and pays him in advance, during the pressing season when oil is abundant and cheap, for a hundred liters over the course of the year. The producer stores the oil in his warehouse, and the buyer comes from time to time and takes from it against his purchase.
A question arises here: at the time of payment, the oil had just come from the press and was full of dregs; but if the buyer returns half a year later, the dregs have already settled, and he takes from the top, receiving clear oil. It would seem that he profits from the deal - he paid for a hundred liters, which in reality contain only ninety-eight and a half usable liters, whereas at the time of taking it, he will receive a hundred liters free of dregs. How do we relate to this?
To this, the Mishnah states: "Af hamocher shemen mezukak lachaveiro" - even one who sells refined oil to his friend. It is worth being precise with the wording: although the words sound like a contractual obligation to provide clean, refined oil, this is not the simple understanding. The parties did not specify anything, but rather agreed on a supply of oil, and in practice, it will turn out that the oil will be refined, because when the buyer comes months later, the dregs will have already settled to the bottom.
The Mishnah continues: "Vechol yemot hashanah, harei zeh mekabel alav log umechtzah shemarim lemeah" - and all the days of the year, he accepts upon himself a log and a half of dregs per hundred. According to Rabbi Yehudah, when the buyer takes his oil during the year, he only has the right to ninety-eight and a half liters, since one must deduct the one and a half that settle to the bottom and are unusable. After all, if he had bought the oil directly from the press and stored it himself, he would not have received more than that.
Practical Halachah:
The halachah does not follow Rabbi Yehudah. According to his view, the producer is allowed to tell the buyer: "If you do not agree to take ninety-eight and a half instead of a hundred, I will mix the containers again and you will take a hundred, but their quality will be lower and you will lose either way. I am saving you the hassle of waiting for the dregs to settle, but do not rob me." The Tanna Kamma holds that he does not have this right: once the dregs have settled, there is no room to start deducting from the value of the oil. The halachah follows the Tanna Kamma - and therefore, one who agrees in advance on a hundred, takes a hundred, and nothing is deducted for him.
A final point: when a contract exists, the terms of the contract are what determine. If it is written in it that the buyer will receive ninety-eight and a half - that is his amount; and if it is written that he will receive a hundred of clear oil - he will receive a hundred. The question of our Mishnah arises only when the parties closed the deal without specifying these terms, and it must be clarified what the law is regarding calculating the dregs that settle over time.