חמץ בפסח אוסר תערובתו בין במינו בין שלא במינו במשהו אפילו בהנאה: הגה וצריך לשרוף הכל ולא סגי בפדיון דמי החמץ ולמכור השאר (מרדכי פ"ק דפסחים ופסקי מהרא"י סק"ד ותשובת מהר"י ברי"ן) מיהו כלים שנתבשל בהם מותרים לאחר הפסח ואין צריכין שבירה או הגעלה: (ד"ע ותוספות פרק כל שעה) ודין תערובתו כדין שאר תערובות אלא שמה שאוסר בשאר תערובות פחות מששים אוסר בחמץ במשהו אבל אם בשאר תערובת לא היה צריך ששים אלא קליפה או נטילת מקום אף בחמץ כן שחם בחם בלא רוטב די בקליפה כשאר איסורים וכן אם נגע ככר חמץ בככר מצה ושניהם חמין ואין שם דבר המפעפען לא אסר אלא מקום מגעו בלבד לפי שאינו מבליע יותר: הגה ובדין ריחא מילתא לענין תבשיל שיש בו חמץ עם שאר תבשילין יש מקילין במקום דהיה מותר בשאר אסורים (מרדכי פרק כל שעה) ויש מחמירין דמשהו מיהא איכא (הגהות סמ"ק ותוס' דע"א) ודוקא במקום ששייך בו ריחא אלא דבשאר אסורים לאו מלתא היא כמו שיתבאר ביו"ד סי' ק"ח בסיעתא דשמיא:

Laws of mixtures of chametz within Pesach: 12 sections Chametz on Pesach makes a mixture forbidden, whether or not the mixture is of the same type as the chametz, in any amount and one cannot even derive benefit from it. And one must burn it all and its not sufficient to redeem the value of the chametz and sell the rest (מרדכי פ"ק דפסחים ופסקי מהרא"י סק"ד ותשובת מהר"י ברי"ן). However, vessels which one cooked this mixture in are permitted to be used after Pesach and don't need to be destroyed or scalded(ד"ע ותוספות פרק כל שעה). The laws of mixture of chametz are the same as the laws of other forbidden mixture, except whereas other mixtures are permitted where less than 1/60 is present, chametz mixtures remain forbidden where any amount is present. But if in the rest of the mixture there was no need for sixty, rather just a peel or taking a place, so to with chametz, it is hot in the heat without a sufficient sauce in the peel like other forbidden mixtures, and if a loaf of chametz touches a loaf of matzah and they are both hot and there is nothing bubbling, only the place of contact is forbidden, since it didn't absorb further. And the law of Reichah Milsah regarding cooked dishes which have chametz in them and other cooked dishes: there is room to be lenient in a place where it would be permitted with regard to other forbidden mixtures((מרדכי פרק כל שעה). And there are those are strict (הגהות סמ"ק ותוס' דע"א). This is all specifically where Reichah is relevant. Rather, regarding other forbidden mixtures, it is not relevant, as we'll see in Yoreh De'ah 98 with Hashem's help

Hametz that was mixed in [even] after 6 hours [still] does not prohibit the mixture with a minimum of "any amount" until the evening. On the contrary, its status is like that of all other prohibited things [and it has a minimum of 60:1]. (Gloss-If it has a spoiled flavor this too permits it.) (Ed.-This is his own opinion based on the general consensus.)

Wheat which was found o the eve of Pesach in cooked chicken: it's permitted when it's less than 1/60. However, if one heated the chicken on Pesach when the wheat was still inside, it reverts to giving the innards taste and is forbidden in any amount. Rema: however, if one heated it in a kli sheini, one need not be concerned. There are those who rule strictly regarding a kli sheini on Pesach and Yom tov, saying if the kli sheini is heated to yad soledes bo, this is not called a kli sheini.

If chometz became mixed in before Pesach began, it is nullified in 60. It does not return and become revivified on Pesach and forbidden even in a minute amount. And there are opinions that disagree with this (and hold it does become revived). Rema: and our custom is like the first opinion regarding all mixtures that is wet within wet. But we forbid if the thing is dry that is mixed (or there is concern that it mixed) like bread that fell into wine; even though it was taken out from the wine, it's prohibited on Pesach because of the concern that maybe crumbs remained in the wine which give taste on Pesach.

Dry meats, cheeses, and fishes when they were saltd before Pesach and we were not careful with them: are permitted for consumption on Pesach. However, fishes which were salted by soaking them in water on Pesach in a chametz vessel: one should be strict and warn against them because they absorbed flavor from the discharge of the vessel on Pesach and any amount of chametz is forbidden on Pesach.There are those who disagree or rule more strictly and in our countries, the custom is to be initially strict not to eat dried cheeses or fishes or meats. However, meats which were thoroughly washed out three times before Pesach: we are accustomed to eating those, [However], Intestines: it's not effective to thoroughly wash them out, therefore we don't soak "dry butcher goods" (מהר"י ברי"ן) . After the fact though, we're not strict with these. However, fat which was melted in a chametz vessel is forbidden in places where there was not caution at the time of making products from chametz, so that there should not be [fats] melting in a chametz vessel which was used within 24 hours (מרדכי ריש פרק כל שעה וסמ"ק והגמ"יי פרק א'). Anything which was cooked in a chametz vessel, such as cooked wine or jam or similiar things, is forbidden on Pesach. However, there are those who are lenient during the final Yom tov. (פסקי מהרא"י סימן קע"ז). And the law is: If a minute amount of these things is mixed into a food, we're not strict to forbid the mixture, so seems appropriate to me. There are those who are strict about using "vinegar wine" which was used throughout the year, for they are concerned that perhaps one might place the remnants [of the wine] from a meal into it and there occasionally may be bread crumbs in [the remnants] (מהרי"ל). In our locales, where "vinegar wine" is not commonly found, I don't see any reason to be strict about this. There are yet others who are strict initially to not fill [barrels] with wine or vinegar wine [with a] chametz utensil within 3o days of Pesach, and if one was filled [with it] within 30 days, they are accustomed to not drink it on Pesach (תשובת מהר"י ברי"ן). And the one who is lenient does not lose, how much more so in places where wine and vinegar are not commonly found, so seems appropriate to me. A barrel of wine whose boards are attached with dough: if its within two months of Pesach, then its still soft and giving taste on Pesach and [therefore] it's forbidden to drink it. And if it was put there before then, it has dried out and its not giving taste and [therefore] it's permitted. However, if there's a "kezayis" of dough in one place, one is obligated to destroy it even though it was made to strengthen [the barrel] (פסקי מהרא"י סי' קמ"ט), as shown earlier in 442:7

Salt that was placed in a mortar is permitted to be used to salt meat on Passover, because it does not release (absorb or emit) when cold.

Unripe produce that was crushed before Passover in leavened mortars is permitted to be eaten on Passover. Gloss: because it does not release when cold; and even if it was prepared during Passover, it is not forbidden if the vessel was clean. However, if it was cut during Passover with a knife used for leaven, one should be stringent, since an ordinary knife is not presumed clean and there is concern for leaven adhering to it (Maharil). But if that item became mixed into a cooked dish, one need not be concerned or be stringent to forbid it out of doubt; כך נראה לי (so it appears to me).

Olives for which care was taken to cut them with a new knife—even if care was not taken to pickle them in a new pot—if the pot had not been used within the previous 24 hours, it is permitted according to all opinions.

Dry mixed with dry: although regarding other prohibitions one part in two is nullified, leaven mixed with matzah—even in a thousand—is not nullified; and there are those who say that leaven is like other prohibitions in this respect.

A substance that imparts a detrimental taste is permitted even on Passover. Gloss: and there are those who are stringent, and such is the custom in these regions; and in a place where the custom is to be stringent, even the slightest amount and even a detrimental taste is forbidden (Terumat HaDeshen §198).

Whether leaven became mixed in before Passover and Passover passed over it, or it became mixed during Passover and the entire Passover passed over it, or Passover passed over the leaven and it became mixed after Passover—it is nullified in sixty; and if there is less than sixty, it suffices to discard the benefit of the prohibition into the Dead Sea (Hagahot Maimoniot, ch. 1).

Inferior leaven (ḥametz nuksheh), even in its own right, is not forbidden for benefit after Passover; but “periyosh” items are considered full leaven and are forbidden for benefit after Passover. Gloss: some refrain from playing on the table during Passover with cards called “kartin,” out of concern that crumbs of inferior leaven within them may fall into food (Piskei Mahari §167).