May I add milk to a hot coffee on Shabbos?
In a previous Halacha Yomis we noted that although food does not usually cook in a kli sheini (a secondary vessel), some foods are kalei habishul and cook easily even in a kli sheini. Since we are uncertain what items are kalei habishul, we avoid placing all food in a kli sheini.
Nonetheless, one may add cold water to a cup of hot tea (if not scolding hot) because it is clear from the Talmud that water will not cook in a kli sheini and is not in the category of kalei habishul. What is the status of milk and fruit juices? Do we treat them as kalei habishul, or are all liquids the same as water? Rav Shneur Zalman of Liadi, the founder and first rebbi of Chabad, wrote in his seminal work Shulchan Aruch Harav (318:12) that all liquids have the same status as water. This would seemingly include milk. Accordingly, it would be permissible to add milk to a cup of hot tea. However, the Mishnah Berurah (318:39) writes that milk may be added to a kli sheini only if it was originally cooked. Apparently, the Mishnah Berurah disagrees with the Shulchan Aruch Harav and does not consider all liquids to be the same as water. (As a side note, although we ordinarily do not reheat liquids that have cooled because “yeish bishul achar bishul bedavar lach”, nonetheless the Mishnah Berurah allows adding cold cooked milk to a kli sheini. Apparently, this is because there is a confluence of two uncertainties: there is minority opinion that allows reheating liquids that have cooled, and the status of milk as kalei habishul is uncertain.)
Is pasteurized milk considered cooked? Typically, milk is pasteurized at 161ºF, and according to Igros Moshe (OC 4:74, Bishul §3) 160ºF is the temperature of bishul. Still, there is a possibility that the pasteurization dipped slightly below 160ºF. Even so, Tzitz Eliezer (14:32) writes that one can add pasteurized milk to a kli sheini because of several considerations. First, many poskim cite the ruling of the Shulchan Aruch Harav that uncooked liquids may be added to a kli sheini. Second, perhaps the Mishnah Berurah (who only allows cooked milk in a kli sheini) does so as a stringency and not as an absolute position. Third, the concern that many foods may be kalei habishul is at most an uncertainty. Fourth, it is unlikely that the temperature of the water in a kli sheini will be greater than the temperature at which the milk was pasteurized, and if so, ain bishul achar bishul will apply even if the pasteurization temperature was less than160ºF. He concludes that since there are so many reasons to be lenient, one may add pasteurized milk to a kli sheini. However, as we noted in a previous Halacha Yomis, there is an advantage to preparing the coffee in a kli shlishi (a third vessel filled from a kli sheni) to avoid the Chayai Adam’s concern of yad nichves (that scalding water in a kli sheini is treated like a kli rishon).
May I add cold water to a hot cup of tea on Shabbos?
In general, raw food may not be placed in a klei rishon on Shabbos, but it may be placed in a kli sheini (a vessel which was filled with liquid from a kli rishon). Raw food will not cook in a kli sheini, because the heat is less intense. However, the Talmud states that certain foods which are “kalei ha’bishul” (that cook easily) will cook even in a kli sheini. In practice, we are uncertain which foods are kalei ha’bishul, and therefore we are generally strict and do not place any raw food in a kli sheini (see Mishnah Berurah 318:42). However, it is clear from the Talmud and poskim that water is not in the category of kalei ha’bishul (see Mishnah Berurah 318:86), and therefore, cold water may be added to a kli sheini.
Still, there may be another concern with adding cold water to a hot cup of tea on Shabbos. The Mishnah Berurah (318:48) cites the opinion of the Chayei Adam that if the hot water in a kli sheini is at the temperature of yad nichveis bo (scalding hot) then the vessel retains the status of a kli rishon, and cold water may not be added on Shabbos. Rav Belsky zt”l estimated that temperatures exceeding 180ºF are considered scalding hot. Igros Moshe (OC 4:74, Bishul §4) was asked if the custom is to follow the stringency of the Chayei Adam. He responded that it is uncertain, but he seemingly recommends being stringent. However, Rav Moshe states that if the hot water is transferred to a kli shlishi (a third vessel), even the Chayei Adam would allow adding cold water.
In summary, cold water may be added to a cup of tea if the water is not scalding hot. However, if the tea is transferred to a third vessel, cold water may be added under all circumstances.
May one add sugar to hot tea on Shabbos?
If food was fully cooked before Shabbos and then cooled down, may it be recooked again on Shabbos? In the language of the Talmud, do we say, Yesh bishul achar bishul (there is cooking after cooking), or Ain bishul achar bishul (there is no cooking after cooking). The Shulchan Aruch makes a distinction between recooking a dry food and a liquid. If a dry item was fully cooked, there is no prohibition to recook it again on Shabbos, but it is prohibited to recook a liquid that cooled down. This does not mean that one may place a dry cooked food on the fire. Though there is no Biblical prohibition of bishul when reheating a dry food, there are nonetheless Rabbinic injunctions which apply, either because one might adjust the flame or because it has the appearance of cooking. However, one is permitted to place a dry fully cooked food into a boiling pot of water that has been removed from the fire. Once the pot is off the stove, there is no concern that one might adjust the flame, and since there is no fire, it does not appear as though raw food is being cooked.
Granulated sugar is extracted via a cooking process. Since sugar is a dry food, one would assume that it should be permitted to add sugar to a pot of boiling water that is off the fire. However, the Mishnah Berurah (318:71) cites the Sharei Teshuva that since sugar dissolves when placed in hot water, lichatchila we view sugar as a liquid. As such, sugar should not be added to a kli rishon (a pot that was on the fire), nor may one pour hot water onto sugar. Instead, one should first pour the hot water into a cup and then it is permissible to add the sugar.
