Question: Is a plastic or aluminum disposable cup allowed to be used for making Kiddush or Havdalah?

Answer: The Gemara[1] lists 10 things that are needed for a "Kos shel Bracha" 1) Rinsing 2) wiping 3) Chai 4) full and 6 other things. The Zohar[2] specifies the first four as obligatory, while the other six are considered "Hiddur Mitzvah"[3].

The Shulchan Aruch[4] cites three definitions for “Chai”. One is, that the cup needs to be "complete" and "whole". The reason for this is, that a broken cup may be compared to "death". Therefore, any cup that is "chipped" or "cracked"[5] is not fit to use for Kiddush or Havdalah. The cup should be made of nice, durable material and used specifically for a "Kos Shel Bracha" purpose[6]. Based on this, a disposable cup should not be used for Kiddush.

There is another reason why a disposable cup should not be used for a  Kos shel Bracha. The poskim[7] write, that a Keli designed for a onetime use does not need Tevilah in a Mikvah before using it. The reason given is that it does not have the status of a keli. Consequently, a Keli designed for one time use, is "not" a Keli with regards to Kiddush and Havdalah [8].

   

However, there is a reason to permit disposable cups for use with Kiddush and Havdalah. Compare to Netilas Yadaim, where a proper Keli is required. However, any vessel that can hold a Reveis of water, is considered acceptable even if it is made of flimsy material[9] . If so a disposable cup should also be considered a proper Keli for Kiddush and Havdalah[10].

L’halacha: The best thing to do is to use a proper silver cup[11] for Kiddush and Havdalah. If a proper silver cup is not available, then a proper "whole cup" should be used[12]. B’dieved [13] where one does not have any other cup, then a disposable plastic or aluminum cup may be used. 

Daily inspiration:

To achieve our potential, we need a proper vessel in which to channel our potential. The lack of a proper conduit leads to frustration and brings about a hit to our self confidence and self appreciation. Our conduit is our intellect and emotion. When we are in a healthy mental and physiological state, they function properly.      

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[1] ברכות נ"א ע"א

[2] תיקוני זהר תיקון מ"ז, ובפ' עקב רע"מ רע"ג:

[3] עי' רמב"ם הל' ברכות פ"ז הט"ו ובשלחן הטהור סעי' ד' (אמנם מלשון אדה"ז לא משמע חילוקים אלו)

[4] שוע"ר סי' קפ"ג:ג-ד

[5] עי' משנ"ב שם סקי"א

[6] שו"ת אג"מ ח"ג סי' ל"ט

[7] עי' שו"ת מנח"י ח"ג סי' ע"ו ע"ז ע"ח, וח"ד סי' קי"ד

[8] שו"ת מנח"י ח"י סי' כ"ג

[9] עי' שוע"ר סי' קנ"ט:ח שו"ת צי"א חי"ב סי' כ"ג ושו"ת אז נדברו ח"ו סי' מ"ח

[10] שם

[11] כף החיים סי' תע"ב סקי"א ע"פ היסוד

[12] אג"מ שם ושו"ת אז נדברו שם

[13] שם ושם (להעיר שיש פסקים דסברי דאפילו לכתחילה מותר מטעם הנזכר בהפנים)