מסכת כלים

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אספקלריא טהורה

A glass mirror is tahor;

and a (glass) dish

that was made into a mirror

is tamei,

and if it was made from the outset

for the purpose of being a mirror

it is tahor (even though it has a receptacle and can be used as a dish).

A (glass) spoon

that (does not stay upright when) one places it on the table

if it can hold the smallest amount

it is tamei,

and if not,

Rabbi Akiva says it is tamei (as it it not meant to hold anything when placed on the table, but is meant to hold things when held in one's hand),

Rabbi Yochanan ben Nuri says is tahor.

כוס שנפגם רבו טהור

A (glass) cup, the majority of (its rim) which is chipped is tahor (as, due to the jagged edges, one cannot drink from it);

if it had three (sips) in most of it (that is, there are three chips to the rim, each of which is less than half the circumference of the rim from the next; as a result, one cannot find a portion of the rim equal to half its circumference without a chip)

is tahor.

Rabbi Shimon says

if it leaks

a majority of the water,

it is tahor.

If it was punctured and fixed,

whether with tin, whether with pitch (neither of which will form a good seal with the glass),

it is tahor;

Rabbi Yosi says

with tin it is tamei (as he held that it could maintain a good seal, if the cup was used gently),

and with pitch it is tahor.