Answer: In the previous Halachot, we have discussed the general law that any new vessels purchased from a non-Jew must be immersed in a Mikveh before using them. We shall now discuss whether or not disposable vessels require immersion.
We have already explained that according to Maran zt”l, plastic vessels do not require immersion even if they are not disposable. We must therefore discuss the law regarding disposable aluminum vessels (such as pans, cookie sheets, and the like) and whether or not they require immersion in a Mikveh.
We find a similar discussion regarding the Mitzvah of Kiddush on Shabbat which must be recited on a cup of wine. The Poskim discuss whether or not a disposable cup can be considered a “vessel” regarding this matter. If a disposable cup is considered a “vessel” regarding Kiddush, it should follow that the same is true regarding immersion in a Mikveh. If so, disposable aluminum vessels would halachically require immersion.
Maran zt”l discusses this topic in his Chazon Ovadia-Shabbat (Volume 2) and he concludes that disposable cups are indeed valid for the Mitzvah of Kiddush according to the letter of the law as they are indeed considered “vessels” and the same would hold true regarding the status of disposable vessels with regards to immersion in a Mikveh. Nevertheless, Maran zt”l adds that since there are several Poskim who differentiate between the laws of Kiddush and immersion, such vessels should be immersed without reciting a blessing in order to avoid a possible blessing in vain.
We must nevertheless point out that many aluminum vessels produced in Israel are not produced by non-Jews; rather, they are manufactured by Jewish companies. Even regarding aluminum vessels produces outside of Israel, there is indeed basis to exempt them from immersion in a Mikveh, for aluminum was a metal which was not yet discovered in earlier generations and the Torah does not delineate an explicit commandment to immerse aluminum. Maran zt”l himself uses this rationale to rule leniently on an unrelated matter (regarding the laws of impurity of a corpse, see Chazon Ovadia-Avelut, Part 2). He quotes that Hagaon Harav Moshe Feinstein zt”l rules likewise. Thus, one need not protest vehemently against those who customarily use such disposable aluminum vessels without first immersing them in a Mikveh, for they indeed have on whom to rely (this is especially true if one is unsure if the owner of the company is Jewish or not).
An Electric Kettle
The Poskim disagree whether or not an electric kettle requires immersion, for we have a rule that anything attached to the ground does not require immersion in a Mikveh since a vessel which cannot become impure does not require immersion and anything attached to the ground cannot become impure. Thus, several Poskim, including Hagaon Harav Shlomo Zalman Auerbach zt”l, write that since the primary usage of an electric kettle is when it is plugged into the outlet, it is considered attached to the ground and does not require immersion. However, halachically speaking, even Hagaon Harav Auerbach did not wish to rely on this reason alone to exempt electric kettles from immersion, for they are used even when they are not connected to the outlet.
Indeed, Maran Rabbeinu Ovadia Yosef zt”l writes that it is preferable to act stringently and immerse an electric kettle in the Mikveh. If one is worried that immersing it in water will ruin it, one should give it to a non-Jew as a gift and then ask him to lend it back to him, for one who borrows or rents a vessel from a non-Jew need not immerse the vessel since he has not purchased them fully and this is no longer comparable to the vessels of Midyan which the Jewish nation took full ownership of. Hagaon Harav Shlomo Zalman Auerbach adds another way to exempt the electric kettle from immersion and that is by giving it to a licensed Jewish electrician who will then take it apart in a professional manner that not just anyone could try at home. The electrician should then put it back together and this will be considered as though one had purchased the kettle from a Jew and it will not require immersion.
Summary: Disposable aluminum vessels produced outside of Israel require immersion in a Mikveh without a blessing. (Some rule leniently on this matter.) An electric kettle likewise requires immersion without a blessing. One can exempt it from immersion by giving it as a gift to a non-Jew and then asking the non-Jew to lend it back to him. Another way to exempt the kettle from immersion is by having a Jewish electrician take it apart in a professional manner and then putting it back together again.