Reference for Avodah Zarah 5:11
גַּת שֶׁל אֶבֶן שֶׁזִּפְּתָהּ גּוֹי, מְנַגְּבָהּ וְהִיא טְהוֹרָה. וְשֶׁל עֵץ, רַבִּי אוֹמֵר, יְנַגֵּב. וַחֲכָמִים אוֹמְרִים, יִקְלֹף אֶת הַזֶּפֶת. וְשֶׁל חֶרֶס, אַף עַל פִּי שֶׁקָּלַף אֶת הַזֶּפֶת, הֲרֵי זוֹ אֲסוּרָה:
A winepress of stone tarred by a gentile [It was the practice to put in a little wine and to coat it over with tar] — he (the Jew) wipes it with water and earth and it is clean (i.e., kosher for use). (If the vat were) of wood, [which requires much tar and absorbs much wine] — Rabbi says: He wipes it [as one of stone]; and the sages say: He peels off the tar. [The halachah is not in accordance with Rabbi.] (If the vat were) of earthenware, even if he peeled off the tar, it is forbidden, [both according to Rabbi and according to the sages; for earthenware, aside from the tar, absorbs the wine.]