One who coats

an undamaged earthenware utensil

Rabbi Meir and Rabi Shimon

rule that [the coating] is tamei [if the utensil becomes tamei];

and the Sages say

one who coats an undamaged [utensil]

[the coating] is tahor,

and if [one coated] a cracked [utensil]

it is tamei.

And similarly [they disagree]

by the (wooden or metal band used as a) reinforcement of a [dried and hollowed-out] gourd-shell (the shell was used to draw water, and the reinforcing band was to keep it from breaking if it hit a stone).

פרק ג משנה ו

The pulp of cynodon (a type of grass)

that was used to coat (as a reinforcement or to prevent leakage from)

pithoi (large earthenware casks used to store water or wine; singular: pithos),

that which touches it

is tamei (as it is considered to be an essential part of the utensil).

The stopper of a barrel

is not [considered to be] attached to it (and so if one becomes tamei, it doesn't spread to the other, even though the stopper is sealed into the barrel with clay).

That which comes into contact

with the coating of an [earthenware] oven

is tamei (as it is a functional part of the oven, helping it retain heat).