Mishnah Mikvaos 9:7: Regarding the aprons of pitch workers and potters and tree-hedgers, they [pitch and myrrh] do not interpose. Rabbi Yehuda says: even those [aprons] of fig driers are like them. This is the general rule: anything which one cares about, interposes; and that which one does not care about, does not interpose.

מִטְפַּחַת שֶׁל זַפָּתִין וְשֶׁל יוֹצְרִין וְשֶׁל מְפַסְּלֵי אִילָנוֹת, אֵין חוֹצְצִין. רַבִּי יְהוּדָה אוֹמֵר, אַף שֶׁל קַיָּצִין, כַּיּוֹצֵא בָהֶן. זֶה הַכְּלָל, כָּל הַמַּקְפִּיד עָלָיו, חוֹצֵץ. וְשֶׁאֵינוֹ מַקְפִּיד עָלָיו, אֵינוֹ חוֹצֵץ:

Mishnah Mikvaos 10:1: Any handles of vessels which were inserted improperly, or which were inserted properly but not secured, or which were secured but they broke, these thereby interpose [i.e. if they are touching something as is being immersed, they prevent it from being purified]. A vessel that was immersed by way of its mouth [i.e. with its mouth face down] is as though it was not immersed. If one immersed it properly [but] without its bottom rim, [it is not pure] until he tips it to its side [so that it will be fully immersed]. A vessel which is narrow at both ends and wide in the middle is not pure until one tips it on its side. A flask with a sunken mouth is not pure until one punctures it on its side [before immersing it]. The ink jar of a commoner is not pure until one punctures it one its side. And the ink jar of Yosef the Priest was punctured on its side.

כָּל יְדוֹת הַכֵּלִים שֶׁהִכְנִיסָן שֶׁלֹּא כְדַרְכָּן, אוֹ שֶׁהִכְנִיסָן כְּדַרְכָּן וְלֹא מֵרְקָן, אוֹ שֶׁמֵּרְקָן וְנִשְׁבְּרוּ, הֲרֵי אֵלּוּ חוֹצְצִין. כְּלִי שֶׁהִטְבִּילוֹ דֶּרֶךְ פִּיו, כְּאִלּוּ לֹא טָבָל. הִטְבִּילוֹ כְדַרְכּוֹ בְלֹא זִבּוֹרִית, עַד שֶׁיַּטֶּנּוּ עַל צִדּוֹ. כְּלִי שֶׁהוּא צַר מִכָּאן וּמִכָּאן וְרָחָב מִן הָאֶמְצַע, אֵינוֹ טָהוֹר עַד שֶׁיַּטֶּנּוּ עַל צִדּוֹ. צְלוֹחִית שֶׁפִּיהָ שׁוֹקֵעַ, אֵינָהּ טְהוֹרָה עַד שֶׁיְּנַקְּבֶנָּה מִצִּדָּהּ. קַלְמָרִין הֶדְיוֹטוֹת, אֵינָהּ טְהוֹרָה עַד שֶׁיְּנַקְּבֶנָּה מִצִּדָּהּ. וְקַלְמָרִין שֶׁל יוֹסֵף הַכֹּהֵן הָיְתָה נְקוּבָה בְצִדָּהּ: