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1. Mid'Rabanan, one is prohibited to use utensils of Nochrim even if they were not used within 24 hours, lest one use utensils that were used within 24 hours.
2. Spits and grates which were used directly on a flame by a Nochri must be purged on a flame.
3. Spits and grates which were used for Kodshim must be placed in boiling water in order to purge the absorbed Kodshim which eventually will become Nosar.
4. A utensil which must be purged from non-kosher food must be placed inside a large utensil which contains boiling water.
5. A Yisrael who purchases a knife from a Nochri must scrape it on a millstone and insert it into untilled ground ten times.
6. Scraping the knife and inserting it in the ground is effective only if the knife will be used for cold food.
A BIT MORE
1. The Torah commands not to use the cooking utensils of Nochrim. The utensils absorbed the taste of non-kosher foods which will exude into the kosher foods. There is an opinion that when non-kosher food with a bad taste becomes mixed with kosher food, it does not prohibit the mixture. Thus, the utensils of a Nochri are forbidden to be used mid'Oraisa only if they were used for non-kosher food within 24 hours. The non-kosher food that was absorbed in the utensils acquires a foul taste after 24 hours.
2. Since they absorbed non-kosher food on a flame, they must be purged on a flame as well.
3. Rav Nachman explains that although spits and grates which were used by a Nochri must be purged on a flame, vessels used for Kodshim are not as stringent because they are constantly in use. The taste which the vessel absorbed from one Korban is purged when it is used for another Korban. Rav Papa explains that spits and grates used by a Nochri are used less often and the absorbed food is more difficult to purge. Rav Ashi explains that spits and grates used by a Nochri absorbed non-kosher food. Kodshim are kosher and only became Nosar after being absorbed.
4. In order to purge a large pot, a lining of dough should be placed around the rim of the pot and water boiled in the utensil until the top.
5. This method is effective only for a smooth knife. If the knife is not smooth, it may have a fatty buildup in the crevices which will not be removed by inserting it in the ground.
6. If the knife will be used for hot food, it must be placed in boiling water.
Index to Revach for Maseches Avodah Zarah