Комментарий к Авода Зара 5:11

שזפתה עובד כוכבים – it is the way to cast upon it a little bit of wine to remove [knots] of pitch.

If a none covered a stone wine press with pitch it may be scoured and is then clean;
But if it was of wood, Rabbi says that it may be scoured and the Sages say that he must peel off the pitch.
If it was of earthenware, even though he peeled off the pitch it is prohibited.
In the time of the mishnah wine presses were sealed with pitch. A little bit of wine was put into the pitch in order to prevent the smell of the pitch from ruining the taste of the wine made in the wine press. Our mishnah discusses a Jew who buys a wine press from a non-Jew. Since the non-Jew used wine, which is yen nesekh, in the pitch in the wine press, the mishnah must teach how to make the wine press “kosher”. In this mishnah and in the next we will learn several rules that are still observed today by those who keep the laws of kashruth.
There are three types of wine presses mentioned by the mishnah: stone, wood and earthenware. Stone is the least absorbent of these materials. Furthermore, stone wine presses do not require much pitch to seal them. Therefore, all the Jew must do is scour the wine press to rid it of any traces of the previous owner’s wine. If the wine press was made of wood, Rabbi [Judah Hanasi] holds that it also may be scoured. However, the Sages hold that he must also peel off all of the pitch. Since wood is more absorbent than stone, and since wood wine presses require more pitch, he must be even more diligent in cleaning before it becomes usable. If the wine press is of earthenware, the Jew may never use it. Since earthenware is very absorbent, there is no way to rid it of the yen nesekh.

מנגבה – with water and ashes [to remove wine from the coat of pitch].

ושל עץ – that requires a lot of pitch, and it absorbs a lot of wine.

רבי אומר ינגב – [it is scoured] with a stone. But the Halakha is not according to Rabbi [Yehuda HaNasi].

ושל חרס – whether [the opinion of] Rabbi [Yehuda HaNasi], whether [the opinion of] the Rabbis, even though he has peeled/scraped off the pitch, it is prohibited, for earthenware without pitch absorbs wine.