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It is a practical matter. It is easier to wash without letting the unwashed hand touch the washed hand if the cup has two handles.
Why the two-handled washing cup?
After the first hand is washed, it is clean and pure. The unwashed
hand, however, is not. If the two hands touch after the first hand was
washed, it is necessary to rewash the first one. ...
As you said -- Shulchan Aruch allows one to use a cold, clean non-kosher dish or cup "derech arai" -- occasionally. No taste will transfer, and if only done on rare occasion, we're not concerned you will forget and use it for hot.
(When we say a non-kosher dish, we mean someone baked ham on this plate; this plate went through the dishwasher, cooled off, ...
The two issues, as I see it, are -- dipping in the mikvah, and any transfer of non-kosher taste.
As for the mikvah -- if it belongs to a non-Jew and the Jew is just borrowing it, there's no obligation to dunk it. The obligation is only on Jewish-owned vessels. If the lender doesn't mind, I suppose you could borrow it and kasher it, which would take care of ...
The Talmud, also in Zevachim later on (97b), identifies the biblical 'mizrak' with the 'agan' (אגן); see also Ex. 24:6. Elsewhere in the Talmud (Ber. 22a), the agan is depicted as a tub that can contain enough water to bathe in (9 kav; aprox. 3 gallons). (In biblical descriptions they are both typically used to illustrate large, excessive/exaggerated ...
Plastic doesn't require tevila but metal does (d'oraita according to many, see OU here under A). As such, if the metallic resistor touches the water (and I assume it does) then you need tevila with a blessing.
On utensils made of metal and plastic, kashrut.com (on top, letter b) writes
A utensil made of a material requiring tevilah should be immersed
Regarding your question the Rash on Keilim 2:5 says:
(Sources provided from Sefaria.org)
ונייר הוא קלף שמכסין בו את הצלוחית כדאמרינן (ב"ק דף מט:) וכי לצור על פי צלוחיתו הוא צריך:
(The) paper (which the Mishna speaks about), is parchment which they use to cover flasks as it says (Bava Kama 49b) "does he need it to cover the opening ...
A number of kashrut certification agencies (led by Star-K and the OU) discovered that plastic packaging material suppliers were using animal-based additives (e.g., tallow, animal fat) in the plastic resins (e.g., as lubricants) and that these additives could migrate into the food. Interestingly the Food & Drug Administration requires these chemicals to ...
See answer to this related question regarding the kashrut of Sodastream for Pesach. According to OU, it is permissible for Pesach use. (I can't qualify it further as my web browser is blocking me from viewing the OU site, now. If someone wishes to edit my question to include what OU says, please do so.)
Sodastream recommends using a new bottle or one ...
There are two places in halacha where this question is commonly addressed: the laws of insects/forbidden organisms in food and the laws of cleaning for Pessah. In both cases the key criteria is visual inspection. The halacha is not concerned with what the eye cannot see.
On cleaning for Pessah
If one is not using the oven on Pesach: The ...
Objects in this category are called "keilim she'm'lachtam l’issur," which means--according to this nice overview of Shabbos 123-124--they may be moved if and only if one needs them (l'tzorech gufo) or the place they are occupying (l'tzorech mikomo) for a Shabbos-approved use. (Cf. "keilim she'm'lachtam l'heter," which refers to items that may additionally be ...
You do not say if the dishes are kosher to start with. Porcelain has a special status as it is earthenware covered by a thin glass layer. That makes it impossible to kasher.
R David Rosenfeld at aish.com writes
In general the practice is not to kasher them. However, in cases
involving great loss, one may wait 12 months, kasher them in boiling
water 3 ...
Rav Ovadia M'Bartenura writes (ibid):
(Source from Sefaria)
משיצרפם בכבשן. וקודם צירוף הן כלי אדמה ואין מיטמאין
When they are baked in the oven: And before this baking, they are earthenware [i.e. not clay] vessels and are not suseptable to Tuma
Based on this, air dried clay vessels would not be susceptible to Tuma.
Hope this helps!
Wikipedia explains how the Britta pitchers are made:
BRITA products include water jugs, kettles and tap attachments, all of
which use silver-impregnated activated carbon and ion-exchange resin
disposable filters as their primary filtering mechanism. The
activated carbon used in BRITA filters is produced from coconut
shells. The company ...
Dairy bread is not uniformly forbidden, there are two exceptions (from OU here)
Dairy bread that has a unique shape is permissible because the shape will serve as a reminder that the bread is not parve
One may bake a small portion of bread which will be consumed in one meal, as it is assumed one will remember the meat status without difficulty.
As such I ...
This page suggests that the matter is complicated and that there is halachic reason for worry unless specifics are well known. It cites a source for kashering seltzer equipment, and suggests there is reason that kashering it for Pesach is necessary:
Da’as Torah, addendum to Hilchos Teraifos ד"ה בזה"ז ** (Rabbi Shalom
Mordechai Shwadron of Berezhan, ...
According to this Star K article, cited by Dan F in this answer:
...The pan will become treif. The rack or grate should not be used for
anything except kashering liver, unless proper kosherization
procedures are employed to kasher the grates, racks, and/or utensils.
Any utensil used in the broiling process, such as a fork, should be
set aside ...