Mikvaos 9:7-10:1
Mikvaos 9:7
The aprons of those who work with pitch, of potters and of tree-trimmers aren’t subject to interpositions; Rabbi Yehuda says that the same is true of those who dry figs. The general principle is that if someone is bothered enough by something to want to remove it, it’s an interposition; if not, then it isn’t.
Mikvaos 10:1
Handles of utensils that were not affixed in the regular manner, or those that were affixed in the regular manner but not firmly or those that were affixed firmly but broken, are all interpositions. If a vessel is immersed with its opening facing downwards, it’s as if it hasn’t been immersed at all. If it’s immersed in the usual way but without its attachment, it’s only purified if turned on its side (so that water can enter the attachment). If a vessel is narrow at each end and wide in the middle, it’s only purified if turned on its side (so that water will fill the middle). A flask whose mouth points downward is only purified if a hole is made on its side (again, for water to enter). A lay person’s inkpot is only purified if a hole is made on its side. The inkpot of Yoseif the kohein had a hole on its side.