the gemara days what is the halocha about using these vessels which are covered in tar?
i want to ask, do the flavors enter only the metallic coating, from which they could be purged, or do they penetrate into the earthenware interior, from which they could not be purged?
moshe yaakov bordon, london, england
I assume you are referring to the Mani d'Kunia - earthen vessels that are coated with Kunia. The Gemara says that these vessels are equivalent to regular earthen vessels - they absorb tastes but do not release them and therefore cannot be rendered Kosher after absorbing forbidden substances.
According to Rashi, Kunia is lead and according to Rabbeinu Tam it is glass. It follows that according to Rabbeinu Tam if the vessel is coated with lead, it can be rendered Kosher by putting it in boiling water. The Shulchan Aruch (OC 451:23) rules like Rabbeinu Tam, but the Mishnah Berurah says that most of the Poskim Achronim are stringent like the opinion of Rashi.
The answer to your question, in short, is that a metal coated earthen vessel, according to Rashi, absorbs tastes into the earthenware interior itself, and according to Rabbeinu Tam it does not.
Kol Tuv,
Yonasan Sigler