- If something permitted was cooked with something forbidden in a kli sheni after the fact the food is permitted. Some are strict unless there is a case of great loss.
- If something forbidden was cooked in a pot or utensil that was a kli sheni the pot or utensil needs to be koshered. Some poskim hold it doesn't need to be koshered.
- The Rama Y.D 94:7 holds that a solid item in a kli sheni is a kli sheni and there's no difference between a solid and a liquid after they landed. Chavot Daat 92:23 cites Minchat Yakov 61:45 writes that even if a dvar gush is like a kli rishon it can't accomplish bishul, so it can't be boleh umaflit kechad.
- A solid item that falls onto something cold according to the Maharshal is considered a kli rishon, while according to the Rama is considered an broken stream iruy. If that solid item is mixed with hot liquids the Rama agrees that even the solid is considered like an unbroken stream iruy since it is mixed in hot liquids.
- If something permitted was cooked with something forbidden in a kli shelishi, after the fact some hold that the food is permitted. Some say that a kli shelishi is the same as a kli sheni.
- If something forbidden is poured onto something permitted or the opposite or meat and milk, the pour can transfer a taste up to the thickness of a peel. The thickness of a peel is the amount that it could be peeled at one time. If hot milk from a kli rishon fell on a meat pot the thickness of a peel of the pot is rendered non-kosher and needs to be koshered. If one accidentally cooked in it without koshering the food is nonetheless kosher.
- If the stream is unbroken there is enough heat to heat up each side and completely transfer tastes one to another. If the stream is broken there is only enough heat to heat up each side but not enough to heat it up and extract a taste and have it absorbed into the other side simultaneously. For example, if hot water in a broken stream poured onto cold cheese which was sitting on a meat dish the cheese and the dish are kosher. Another example is that it is permitted to pour with a broken stream hot water on chickens which weren't salted since the heat of the stream isn't enough to heat up the blood and to have it get absorbed into the chicken.
- If an unbroken stream of hot liquids overflow from a pot on the fire and go along a surface until it touches something it is considered an unbroken pour to transfer taste up to a peel. If the stream is broken it is considered a kli sheni.
- A solid piece of food that is picked up on a fork or with one's hand is considered a kli rishon until it is placed on the plate or bowl.  As it is being placed down on the plate or bowl that is considered iruy. After it settles it is considered a kli sheni.
Mavliya Umaflit K'echad
- According to the Taz a kli sheni can be mavliya or maflit but not both simultaneously.
- According to the Shach, an unbroken stream can be mavliya umaflit kechad but a broken stream can be mavliya or maflit but not both simultaneously.
- According to the Chavot Daat an unbroken stream on a cold surface can be mavliya or maflit but not both simultaneously.
- According to Chavot Daat a dvar gush can be mavliya or maflit but not both simultaneously. Magen Avraham argues that it can do both simultaneously.
- What does that mean that something can't be mavliya and maflit simultaneously?
- Taste doesn't transfer from one solid to another solid (Pri Megadim M"Z 105:4).
- Taste doesn't transfer from one solid to another through a liquid (Dagul Mirvava 105:3).
- Taste doesn't transfer from a liquid to a liquid through a solid (Chavot Daat 92:22).
Not Yad Soledet Bo
- A kli rishon that isn’t yad soledet bo one shouldn’t use initially for something that isn’t kosher. After the fact it could make something non-kosher up to a klipah.
- A kli sheni that isn’t yad soledet bo one shouldn’t use initially but after the fact it doesn’t make something non-kosher at all.
- Roasting something forbidden together with something permitted will make the permitted thing forbidden up to the thickness of a Etzbah where they touched.
- A food which absorbed a taste of something forbidden can't forbid something else with roasting unless it is fatty. Even Ashkenazim agree that in this case we don't assume that all foods might be fatty.
- A dry kosher food that was roasted on a non-kosher utensil only absorbs up to a peel. If the kosher food was wet it would absorb up to a Etzbah.
- A non-kosher food that was roasted on a kosher utensil the utensil absorbs up to a peel.
- A kosher food that absorbed non-kosher tastes which was then roasted without liquids on a kosher utensil the utensil remains kosher.
Pressure of a Knife (Duchka Dsakina)
- If a cold knife is used to cut a non-sharp food there's no transfer of taste between the food and the knife.
- If a cold knife is used to cut a sharp food there is a transfer of taste up to a thickness of a Etzbah and for Ashkenazim initially there is a complete transfer.
- If a knife is used to cut a non-sharp food that is in a Kli Rishon whether it has liquids or solids there is a complete taste transfer.
- If a knife is used to cut a non-sharp food that is in a Kli Sheni there is a major dispute but most hold that there is only a transfer of a peel.
- If a knife is used to cut a non-sharp food that is in a Kli Shelishi most say that there is a taste transfer of only a peel.
- If a knife is used to slaughter an animal according to Sephardim there is no transfer of taste at all, while according to Ashkenazim there is a transfer of taste up to a peel into food but not into the knife since utensils don't absorb as easily as food does.
- If a knife isn't used within 24 hours it doesn't transfer taste.
- Shulchan Aruch Y.D. 105:2. The Rashba Torat Habayit 1b quotes someone who says that just like a kli sheni doesn't cause Bishul (Shabbat 40b) it doesn't cause any transference of taste. The Rashba himself disagrees based on Chullin 8a and Chullin 8b. He held that even though a kli sheni doesn't cause bishul it does cause a transference of taste. The Tur 105:2 understands that the Rashba himself would say that a kli sheni could only transfer taste up to a klipah but himself argues that perhaps it transfers taste completely. The Shulchan Aruch Y.D. 105:2 cites the lenient opinion who says that it doesn't transfer taste as well as the Rashba that it transfers taste up to a klipah. He says initially one should be strict for the Rashba. Aruch Hashulchan 91:19 follows Shulchan Aruch. However, Shach 105:5 and Taz 105:4 cite the Maharshal who holds that a kli sheni can transfer taste completely and advise being strict. Badei Hashulchan 105:39 is strict unless there is a great loss in which case one can rely on Shulchan Aruch. Chachmat Adam 59:6 says that a klipah is necessary unless there is a loss.
- Based on the dispute cited above, the utensils that were made non-kosher because of a kli sheni should not require koshering according to the lenient opinion and should require koshering according to the Rashba. Shulchan Aurch 105:2 is initially strict for the Rashba. Rama YD 94:7 and 95:3 and Torat Chatat 33:1, 58 hold that a utensil that was absorbed something non-kosher in a kli sheni doesn't need to be koshered. However, Minchat Yakov 33:3, Rabbi Akiva Eiger 105:6, Badei Hashulchan 105:39, and Horah Brurah 105:28 write that one should be lenient to kosher something that became non-kosher because of a kli sheni unless it is a loss. Yabia Omer OC 3:24:1 implies this as well. His proof is from the Rif Pesachim 8b, Rosh Pesachim 2:7, Shulchan Aruch O.C. 451:5, Tur and Bet Yosef Y.D. 121:3-5 who say that a kli sheni requires koshering.
- The Rama cited by Shach 105:8 answers how a bug poured in hot liquid could transmit taste to the utensil it falls upon that it is treated as an iruy since it is mixed in with other hot liquids. Shaarei Deah Luria 99:1 p. 438 explains further that if it wasn't mixed in it would be considered a broken stream iruy which wouldn't forbid the utensil since it couldn't be mavliya umaflit k'echad. However, since it is mixed in with hot liquids it is considered an unbroken stream iruy and can be maliya umaflit k'echad.
- Horah Brurah 105:29 writes that even though some are strict regarding a kli sheni there's no need to be strict regarding a kli shelishi. Shevet Halevi 8:181 agrees. Badei Hashulchan cites the Pri Chadash who is strict. See Chatom Sofer YD 95.
- Badei Hashulchan 94:101 citing Pri Chadash 68, Aruch Hashulchan end of 94, Chazon Ish OC 52. See however, Shaar Hatziyun 451:10 who distinguishes between kli sheni and kli shelishi.
- Shulchan Aruch 91:4, Shach 105:5
- Badei Hashulchan 91:30
- Chachmat Adam 59:4 writes that based on the Shach 69:65 we always have sixty times the peel of a pot in the food cooking in it.
- Shach 105:5. See however Badei Hashulchan 92:184 that from Shach 92:38 it seems that a broken stream that was originally heated up by the fire is like a kli rishon. Though, Chazon Ish 9:6 cited by Badei Hashulchan maintains that a broken stream is never more than a klipah.
- Rama 95:3. Igrot Moshe YD 1:42:2 explains that the Rama would consider it to be mavliya umaflit kechad even when pouring hot water on cheese that was stuck onto a meat dish since the water needs to heat up the cheese and also enable its absorption into the dish. This is also evident from Chavot Daat 92:23.
- Shach 105:5
- Pri Megadim M"Z 92:26 raises the possibility that this definition of a stream even though it is on a cold surface is only if the stream is connected to a pot on the fire but not to a kli rishon off the fire. He concludes that one shouldn't be lenient even if it is off the fire.
- Trumat Hadeshen 181 and Rama 92:7. Chavot Daat 92:23 writes that even though the stream doesn't cool down since it isn't broken it doesn't cook (or boleh umaflit kechad) since it is on a cold surface.
- Trumat Hadeshen 181 and Rama 92:7. The Pri Megadim M"Z 92:26 explains that even though usually a broken stream can transfer taste up to a peel, since the stream ran along a cold surface if it is broken it is certainly considered a kli sheni. Badei Hashulchan 92:147 agrees.
- Badei Hashulchan 106:21 outlines three approaches as to why the food while in the air is still considered a kli rishon. 1) According to the Maharshal (Yam Shel Shlomo Gid Hanesheh 44, Kol Habasar 75) any solid food (Gush) is considered a kli rishon. 2) Solid food that is in the air that didn't land is considered a kli rishon.(Chazon Ish 9:5) 3) Any food that is in the air that didn't land is considered a kli rishon. (Shach 105:5)
- Shach 105:7 citing Darkei Moshe 105:4 clarifies that a hot food that is placed on a plate or bowl is considered iruy while it is being placed down. However, after it settles it is considered a kli sheni.
- Taz 105:4
- Shach 105:5
- Chavot Daat 92:23
- Chavot Daat 92:23 citing Minchat Yakov 61:45
- Magen Avraham 318:45
- Ateret Moshe Aharon p. 242 provides three examples of what it means that something doesn't mavliya umaflit k'eched.
- Pri Megadim M”Z 105:4 writes using a kli rishon even if it isn’t a yad soledet bo it is an issue even after the fact. That’s the implication of Torat Chatat 23:3 and 33:1. Badei Hashulchan 105:2 s.v. lechatchila cites the Pri Megadim and seems to agree.
- Pri Megadim M”Z 105:4 writes that the Shach and Taz conclude that if a kli sheni isn’t yad soledet bo it doesn't make something forbidden at all after the fact. But initially it is an issue up to a klipah. Badei Hashulchan 105:2 s.v. lechatchila cites the Pri Megadim and seems to agree.
- There are three opinions of how far roasting can transfer taste. The Rashba thinks that essentially it could only transfer up to the thickness of a peel. But he is strict for the opinion of Tosfot for any question of Biblical nature. Tosfot Chullin 99b s.v. ad and Rosh Chullin 7:24 hold that it could transfer up to the thickness of a netila, which is an Etzbah. Lastly, the Ri Halavan (cited by) holds that roasting can transfer taste completely just like cooking. Shulchan Aruch follows the Rashba. Maharshal follows the Ri Halavan but the Shach disagrees.
- The Rashba cited by Shulchan Aruch 105:7 holds that taste absorbed in a food can't impart taste with roasting unless it is fatty. Maharshal in Yam Shel Shlomo Chullin 7:45 and Isur Vheter LMaharshal siman 37 writes that ein beluah yotzei blo rotev only applies to tata gavar or two pieces next to one another but it doesn't apply to tzeli or melicha. He explains that he is following the Ri Halavan that tzeli and melicha transfer taste completely just like cooking. Shach 105:18 quotes the Maharshal and disagrees.
- Shach 105:17-18 is lenient for an absorbed forbidden taste to not assume that all foods are fatty since anyway the question of whether a fatty absorption spreads from one food to another is a dispute between the Rashba and Maharam.
- Shulchan Aruch 94:8, Rama 105:7, Shach 105:23, 94:33, Horah Brurah 105:71. Bet Yosef 95:1 s.v. masati writes that roasting on a utensil transfers a Etzbah, but see Shach 94:9.
- Taz 94:15 implies this but the Pri Megadim vehemently argues that this is an incorrect reading of Shulchan Aruch. Nonetheless, the Badei Hashulchan 94:105 based on Chazon Ish 22:6 rules like the implication of the Taz that food roasted on a utensil only enters the utensil up to a peel. See however, Shulchan Aruch 92:5.
- Taz 105:16
- Shulchan Aruch YD 96:5
- Shulchan Aruch YD 96:1. In the rishonim there are three opinions of how far a sharp food transfers taste when cut. Some say it transfers taste up to a peel (Rosh Chullin 8:31), some say up to a Etzbah (Raavad cited by Torat Habayit Haaruch 4a), and some say completely (Rashba Torat Habayit Hakatzar 4a).
- Shulchan Aruch YD 94:7. The Bet Yosef asks why there is a complete transfer if a Kli Rishon could transfer taste from a utensil to a food up to a peel. He answers that a knife has the ability to transfer more taste and instead of it only going up to a peel, it transfers completely. The Bet Yosef gives another answer that acknowledges that the knife doesn't transfer taste completely unless there is fat on the knife. Also, the Shach has a third answer which would yield the same position about knives in a Kli Rishon. Nonetheless, the poskim are strict for the first answer of the Bet Yosef alone (Badei Hashulchan 94:76 citing Pri Megadim).
- Pri Chadash 94:23 argues that there is an absorption up to a Etzbah. His proof is the Rashba Chullin 111b who states that the Raavad compared cutting with a hot knife non-sharp foods to cutting a sharp food with a cold knife and both transfer taste up to a Etzbah.
- In the poskim there are three possible approaches:
- The Torat Chatat 61 holds that there is no transfer of taste in a Kli Sheni even if there is also pressure of a knife. There is only a transfer from the knife when it is dirty with fat left on it. This is cited by Rabbi Akiva Eiger 94:9.
- The Rama 94:7 holds that there is a transfer of taste up to a peel when the pressure of a knife is used in conjunction of a Kli Sheni. His proof is the Gemara Chullin 8b that the pressure of a knife together with the temperature of an animal's neck at the time of slaughtering cause a transfer of a peel. The Gra 94:27-8 cites this proof.
- The Maharshal (Chullin 7:44 and 8:71) holds that there is a complete transfer of taste for two reasons. 1) He holds that generally a kli sheni causes a complete taste transfer. 2) He holds that a solid item from a kli rishon isn't considered a kli sheni, it is still considered a kli rishon in which case it causes a complete taste transfer. Taz 94:14 accepts the first argument and the second argument he generally doesn't hold of except for when there's pressure of a knife.
- The Chatom Sofer 95 writes that we treat a kli shelishi like a kli sheni, while the Pitchei Teshuva 94:7 writes that we treat it more lenient. Rama 94:7 writes that a kli sheni with pressure of a knife only requires a peel.
- If a person slaughters a kosher animal with a non-kosher knife there is a dispute in Chullin 8b whether the meat absorbs non-kosher taste. One opinion is that it doesn't and simply needs to be washed, while the other opinion is that it transfers a taste up to a peel. Ashkenazim follow the opinion that there is a transfer of taste up to a peel (Rama 10:1, Shach 10:9), while Sephardim follow the opinion that the meat can be washed. On the other hand, if a person slaughtered a non-kosher animal with a kosher knife the gemara has another dispute whether the knife becomes non-kosher but the halacha according to everyone is that the knife remains kosher (Shulchan Aruch YD 10:3). Rashi Chullin 8b s.v. vhilchata explains that the reason to be more strict on food than the knife is that food absorbs more easily than utensils.
- Shulchan Aruch 94:7