Keilim3: 5
[ה] הַטּוֹפֵל כְּלִי חֶרֶס הַבָּרִיא — רַבִּי מֵאִיר וְרַבִּי שִׁמְעוֹן מְטַמְּאִים. וַחֲכָמִים אוֹמְרִים: הַטּוֹפֵל אֶת הַבָּרִיא — טָהוֹר, וְאֶת הָרָעוּעַ — טָמֵא, וְכֵן בְּחִדּוּק הַקֵּרוּיָה.
[If] one coats a sound earthenware utensil, R’ Meir and R’ Shimon rule [the coating] tamei, but the Sages say: [If] one coats a sound [utensil, then the coating] is tahor, but [if one coats] a fractured [utensil, the coating] is tamei. And the same applies to the reinforcement of a gourd-shell.