Kelim, Chapter Thirty, Mishnah One
Chapter thirty, the final chapter of Kelim (phew!), deals with the rules of purity that relate to glass vessels.
1) Glass vessels–those that are flat are pure and those that have receptacles are susceptible.
2) After they are broken they become clean.
a) If he again made vessels of them they become susceptible to uncleanness from that point and onward.
3) A glass tray or a flat dish is pure.
a) If it has a rim it is susceptible.
4) The concave bottom of a glass bowl or plate which was adapted for use is pure.
a) If it was polished or scraped with a file it becomes susceptible to uncleanness.
Section one: This general rule was already taught in 15:1.
Section two: Once a glass vessel is broken, it is not usable. Therefore it is pureit loses any impurity that it once had, and it is not susceptible to impurity.
If one repaired the glass such that it could again be used, it is considered a new vessel and is susceptible to impurity from that point and onward. It does not regain its old impurity.
Section three: These glass vessels are usually flat. Therefore, they are pure. However, if they have a rim, they are susceptible to impurity because they have a receptacle.
Section four: This section refers to the bottom of a bowl or plate that remained after the bowl or plate was broken. The person then made some modification so that he could use them. Despite the fact that these do now have a receptacle, and would seem to be susceptible to impurity, they are still pure because the edges are still rough. However, if he polished the edges, the vessel is now susceptible to impurity because it is finished.