Question: [Wednesday, 11th Nissan, 5781]
Am I required to Kasher my kiddush cup for Pesach? As far as I know I have never used it for Chametz [all the wines that we use are Kosher for Pesach year-long]. Also, I have heard that kiddush cups that have lips on top [which I believe is almost by all kiddush cups that I know], cannot be used on Pesach even if they are Koshered. Is this correct?
One is to Kasher his kiddush cup for Pesach with Hagalah. It is true that some are stringent to not Kasher a kiddush cup that contains a lip due to worry that Chametz has gotten stuck within the crack of the rim, and thus Hagalah does not help, and therefore they put it away for Pesach and purchase a new kiddush cup to be used only for Pesach. Nonetheless, from the letter of the law one does not have to suspect for the above, and at the very most can simply wash it very well using soap and a shiner and use a needle to pick through the grooved area of the lip to remove any possible crumbs. However, one should not place a flame by the lip or use bleach, as doing so can ruin the silver.
Explanation regarding the need to Kasher: One is to Kasher his kiddush cup for Pesach with Hagalah as at times Chametz soaks for 24 hours inside the liquid that is in the cup and it is considered like the Chametz was cooked in it. This is certainly possible by wine of which it is common to dip biscuits or pastries inside of them and perhaps some crumbs have remained in their liquid for the above amount of time. Likewise, some people drink beer in their cups and the beer remains in the cup for 24 hours. Now, although this is only the minority use of the cup, while its majority use is for cold foods, nevertheless, it is subject to the dispute in Poskim as to whether we follow majority or even minority use, of which we conclude that Lechatchila we suspect for the stringent opinion. Likewise, as times one washes the cup with hot water together with other Chametz, and at times the cup soaks in the Chametz sink water for 24 hours. This is in addition to the fact that one may have poured hot Chametz over it while it was in or near the sink.
Explanation regarding if it contains an upper lip: From the letter of the law, a Kiddush cup may be Kashered even if it contains an external upper lip, as we only suspect for cracks in a vessel when the crack is inside the vessel where the food rests and not when it is outside. Nonetheless, I have heard from various Rabbanei Anash that we do not Kosher the kiddush cup if it has an upper lip as we suspect that upon drinking from the cup one has gotten Chametz that is within his mouth into the crack of the lip. Practically, in my opinion one can do as stated above and Kosher it, and so is the widespread custom of Jewry.
Sources: See Admur 451:72 and 21 regarding the need to Kosher a cup, and 451:19 regarding that only an internal lip is an issue. Rabbanim who has told me that we don’t Kosher it: Rav Asher Lemel Hakohen and Rav Eliyahu Landau.