On שבת to avoid cooking (בישול) when preparing hot drinks, such as tea or coffee, we pour hot water from the urn (כלי ראשון) into a second vessel (כלי שני), and from the כלי שני to the third vessel (כלי שלישי) where one can prepare the tea without worry of בישול.

According to R' Moshe Feinstein the minimum temperature for cooking (יד סולדת בו) is 110 degrees fahrenheit (but could be as high as 160 degrees https://en.wikipedia.org/wiki/Yad_soledet_bo). Frequently, near the equator, the outside temperature can rise above the temperature of יד סולדת בו.

Assuming that the temperature of יד סולדת בו is 110 degrees, and the outside temperature is above 110 degrees, would one be required to use a כלי שני between pouring from a hot water urn to a cup to prepare a hot drink since everything outside would be at a cooking temperature?

EDIT: Assume (1) the tea leaves are already outside and cooking (roasting) and (2) איו בישול אחר בישול (there is no cooking after cooking) applies to all forms of cooking, not for different types of cooking (i.e. roasting, baking, boiling, etc...)

  • Note not everyone agrees that one can prepare tea/coffee/etc. in a Kli Shlishi
    – Double AA
    Commented Jun 30, 2017 at 15:38
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    I think within this mix comes the entire question of whether solar heating (I mean directly by the sun) is considered bishul. One of my MIT friends used a giant magnifiying glass hung by a window and left a pot of water on the stove before Shabbat. In the morning, the sun would beam through the glass and that beam went into the pot of water and boiled it. IIRC, his rav said this was permitted since the sun's rays is not considered bishul.
    – DanF
    Commented Jun 30, 2017 at 16:07
  • "Assuming that the temperature of יד סולדת בו is 110 degrees" This seems like a terrible assumption since R Moshe only said the minimum possible is 110. Is that what you mean to assume?
    – Double AA
    Commented Jun 30, 2017 at 16:26
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    You are relating the concept of keli rishon, sheni etc to the idea of temperature. The Chazon Ish holds that temperature is the key criterion. As far as the keli concept is concerned, the "number" of the keli is the key criterion. It seems to me that this is independent of the nature of the keli. So an expanded polystyrene cup will have the same keli "number" as a heavy earthenware cup. Commented Jun 30, 2017 at 16:53
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    @AvrohomYitzchok I think your info is sufficient to be an answer. Using your info, I'll remind myself not to spend Shabbat in Death Valley. I was planning to have tea, there.
    – DanF
    Commented Jun 30, 2017 at 17:25

1 Answer 1


Tosfos writes (in Shabbos 50b)

ושמע מינה כלי שני אינו מבשל - תימה מאי שנא כלי שני מכלי ראשון דאי יד סולדת אפי' כלי שני נמי ואי אין יד סולדת אפילו כלי ראשון נמי אינו מבשל ויש לומר לפי שכלי ראשון מתוך שעמד על האור דופנותיו חמין ומחזיק חומו זמן מרובה ולכך נתנו בו שיעור דכל זמן שהיד סולדת בו אסור אבל כלי שני אף על גב דיד סולדת בו מותר שאין דופנותיו חמין והולך ומתקרר:

Q: What's the difference between a Kli Sheni and a Kli Rishon? If it's Yad Soledes, then both should cook and if not, then neither should cook.

A: Since a Kli Rishon was on the fire, the walls keep the heat inside, while a Kli Sheni's (cool) walls cool off the food [(which presumably prevents cooking)].

So, according to Tosfos, the concept of "Kli Rishon/Sheni" is precise. It's the walls which cause cooking and not the fire.

  • B"N, I'll try to read the physics SE, after Shabbat. But, from my knowledge of meteorology, this is not a universally true statement, at least not in meteorology. Generally, the ground temperature is warmer than the air above it which during the summer explains largely why thunderstorms form. Also, all the professional tennis players know that the concrete is significantly hotter than the air temperature.
    – DanF
    Commented Jun 30, 2017 at 20:16
  • @DanF sorry, the physics.SE link was referring about something else. I was assuming that the cup was taken out from room temperature, which would take a while to heat up. Commented Jun 30, 2017 at 20:43
  • @DanF Although it would probably depend if Toldos Chama is patur because it's cold, or because it's inherently not bishulable. Nafka Minah is this case with a Yad Soledes Cup (fairly practical case - a dark cup left out in Israel, or in a greenhouse). Commented Jun 30, 2017 at 20:49
  • was the OP not asking specifically when the room temperature is above yad soledet, so the kli shaini is Toldos Chama
    – hazoriz
    Commented Jun 30, 2017 at 22:36
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    @ShmuelBrin I suggest that you contact the author of "Yeshivish" and have him add "bishulable" to the dictionary.
    – DanF
    Commented Jul 2, 2017 at 2:28

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