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1. Earthenware and vessels made of Neser (white earth) have the same laws.
2. All metal vessels can become Tamei.
3. Even though glass is like metal regarding Tum'ah, the Gemara records a difference between them.
4. The Gemara notes another difference between glass and metal utensils.
5. Rav Ashi argues that glass is more like earthenware than like metal.
A BIT MORE
1. Some of the laws they share are: both become Tamei when a Tamei object enters their airspace; they do not become Tamei when something Tamei touches the outside of the vessel.
2. This is true whether they are containers meant to hold things, or whether they are flat and cannot contain anything.
3. If a Tamei metal vessel is broken and thereby becomes Tahor, and then it is put back together, it regains its original status of Tum'ah. In contrast, a glass vessel that is broken and then repaired does not return to its original status of Tum'ah.
4. While metal utensils can become Tamei whether it is a container or not, a glass utensil can become Tamei only if it is a container. The Rabanan instituted this difference to ensure that people remember that the Tum'ah of glass utensils is mid'Rabanan, so that they not come to burn Terumah or Kodshim that was in contact with such a vessel. (Burning Terumah or Kodshim is done only when it comes in contact with Tum'ah which is mid'Oraisa.)
5. Even though glass becomes Tamei from the outside of the vessel like metal and unlike earthenware, this is because it is transparent. Accordingly, when a Tamei object touches the outside of the glass vessel, it is considered as though it has touched the inside of the vessel.
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