BT BM 40a(51) :חפו בכופרא‏ : they coat (the wine jugs) with pitch
See the entire entry for kŭp̄or, kup̄rā n.m. pitch; henna

BT BM 40a(51) :חפו בקירא ^דלא^ {ד}מייץ טפי‏ : they coat (the wine jug) with bitumen, and it does not absorb much
See the entire entry for qīr, qīrā n.m. sticky sealant