Gemara

Question (Rami bar Chama): If an elephant swallowed a basket, and excreted it, what is the law?

The case is, it swallowed reeds, and they were made into a wicker basket. If we consider the reeds to have been digested, the basket is Klei Gelalim (of dung), which is not Mekabel Tum'ah. If not, it is Mekabel Tum'ah;

(Mishnah): Kelim made of stone, Gelalim or earth are not Mekabel Tum'ah, not mid'Oraisa nor mid'Rabanan.

Chulin 107a Question (Rav Sheshes): Are you particular about the Kli for Netilas Yadayim?

Answer (Ameimar): Yes.

(Rava): If one fixed a plug of a barrel, it may be used to wash the hands;

Leather water pouches may be used to wash the hands;

A bag or box, even if it holds a Revi'is, may not be used to wash the hands

Berachos 51a (R. Zeira): Ten things were said about the Kos Shel Berachah (the cup of wine over which we say Birkas ha'Mazon):

It must be washed and rinsed. It must be Chai and full. One receives it with both hands, and puts it in his right hand. He lifts it a Tefach off the ground...

Yadayim 1:2 (Mishnah): All Kelim are Kosher for Netilas Yadayim, even of stone, Gelalim or earth.

Rishonim

Rambam (Hilchos Kelim 2:1): If one makes any Kli that can hold something, it is Mekabel Tum'ah mid'Oraisa. This is if it is made of something that endures. A Kli of untanned hide, paper, pomegranate peels or nut shells, even if children made it to measure earth, is Mekabel Tum'ah. A Kli made from a turnip, Esrog or gourd is Tahor, for it will endure only a short time.

Rambam (5:7): If one can put things in a wicker basket and take them out, it is Mekabel Tum'ah. If one must tear it or untie it to remove the contents, or he intended to eat the contents and discard the Kli, it is Tahor. Similarly, a horn that one uses and discards it, it is not Mekabel Tum'ah. If one intended (to keep it for further use), it is Mekabel Tum'ah.

Tosfos (69b DH Klei Gelalim): In Shabbos (16b), Rashi explained that Gelalim is marble. Our Gemara proves that it is dung.

R. Shimshon (Yadayim 1:2 DH bi'Chlei): One may wash from any Kli, of wood, bone glass, even of cattle dung, even though they are not considered Kelim regarding Tum'ah.

Tosfos (Shabbos 76b DH Kedei): Some say that 'Chai' refers to the cup itself. This is proper, for everything else mentioned (about the Kos Shel Berachah) refers to the Kli, and not to the wine. 'Chai' can mean Shalem (complete), e.g. if one ate nine minced ants and one Chai... (Makos 16b)

Poskim

Shulchan Aruch (OC 159:1): Netilas Yadayim is only from a Kli. All Kelim are Kosher, even of Gelalim, stone and earth. It must hold a Revi'is. If it has a hole through which liquids can enter, even if it holds a Revi'is below the hole, one may not wash from it.

Beis Yosef (DH Ein): The Rashba (Chulin 107a DH Hai) brings from Bahag that we are concerned for the Keli because Chachamim enacted Netilas Yadayim like Mei Chatas (water sanctified with ashes of the red heifer). Alternatively, it is like Kidush (washing) hands and feet in the Mikdash.

Magen Avraham (2): Klei Gelalim are not Mekabel Tum'ah, for they are not considered Kelim.

Mishnah Berurah (3): Even though they are not considered Kelim at all regarding Tum'ah, in any case they are Kelim, so they are Kosher for Netilas Yadayim.

Mishnah Berurah (2): Also Kelim of wood, bone, glass or leather, that are special to hold liquids, are Kosher.

Mishnah Berurah (4): Kelim of earth were dried in the sun. If they were fired in a kiln, this is earthenware.

Shulchan Aruch (OC 183:3): One must pursue to get a complete cup (over which to say Birkas ha'Mazon).

Beis Yosef (DH u'Mah): The Rif says that the wine in the Kos Shel Berachah is Chai (undiluted) until Birkas ha'Aretz. The Rosh and R. Yonah explain like R. Tam, that it is diluted less than normal. Tosfos (50b DH Modim) says that Chai refers to the cup. It must be complete, and not broken.

Magen Avraham (5): Even if the base is broken, it is Pasul, unless it is pressed circumstances.

Mishbetzos Zahav (1): Even if it holds a Revi'is below the hole, this is not Shalem. Eliyahu Rabah says that even if there is a nick in the brim enough for a fingernail to get caught in (this is not Shalem). This is a stringency. B'Di'eved it is permitted if there is no other cup, like we say about a Pagum cup (from which someone drank - 182:7).

Mishnah Berurah (10): The Shulchan Aruch connotes that it is merely l'Chatchilah, but it is not Me'akev.

Mishnah Berurah (11): Shalem means that the cup itself is not broken and has no blemish in the brim, even a small Chisaron. (L'Chatchilah one should be stringent about a crack, even without any Chisaron.) Even if the cup itself is Shalem, just the base is broken, one should be stringent, even if it can stand on its base. If he has no other cup, he can be lenient about all this. If a cover for a Kli was not made to hold things, one should not be stringent if he has no other Kli.

Kaf ha'Chayim (14): The Zohar requires that the Kli be Shalem.

Kaf ha'Chayim (15): If the base of a glass cup broke, and one made a metal base, Beis Shlomo (OC 31) did not want to be Machshir.

Kaf ha'Chayim (16): Eliyahu Rabah says that perhaps we disqualify Chisaron only if a fingernail could get caught in it, but a crack of any size disqualifies. Also Chayei Adam, Kitzur Shulchan Aruch, Chesed la'Alafim and Ben Ish Chai say so.

Kaf ha'Chayim (17): Eliyahu Rabah permits a cover for the cup of Birkas ha'Mazon. This is unlike Netilas Yadayim, which requires a Kli made to hold liquid. If possible, one should use a proper Kli.

Shulchan Aruch (OC 271:10): We require for the Kos of Kidush everything required for the Kos of Birkas ha'Mazon.

Beis Yosef (DH u'Mekadesh): The Gemara mentioned Pagum (someone drank from the cup) only regarding the Kos Shel Berachah. Kidush and Havdalah are considered Kos Shel Berachah. The Rambam (Hilchos Shabbos 29:7) holds that all laws of the cup of Birkas ha'Mazon apply to the cup of Kidush.

Mishnah Berurah (43): If the only cup is Pagum, at night perhaps it is better to say Kidush on bread.

Igros Moshe (OC 3:39): The Shulchan Aruch rules like Tosfos, who requires the Kos Shel Berachah to be Shalem. The Kos of Kidush requires everything needed for the Kos of Birkas ha'Mazon. Only a nice cup is Kosher for Birkas ha'Mazon and Kidush. The Magen Avraham disqualifies if the base is broken, even if the cup itself is whole. A paper cup, which is used only once, is worse. It has no importance. If no other cup is available, perhaps one may be lenient.

Minchas Yitzchak (10:23): Igros Moshe was unsure if one may be lenient when there is no other cup. The Shulchan Aruch says 'one must pursue to get a Shalem cup'! The Mishnah Berurah derives that this is only l'Chatchilah. What is the source to be stringent if no other cup is available? The Igros Moshe said that perhaps a paper cup is worse (than a broken cup). This is the reasoning to be stringent.

Minchas Yitzchak (ibid.): The Mishnah Berurah (183:11) discusses when one may be lenient. This is difficult, for the entire Halachah is only l'Chatchilah! The Mishnah Berurah connotes that if it cannot stand on its base, this is worse than a cup that is not Shalem. It is not considered a cup at all, like we say about Netilas Yadayim. He cites Olas Tamid, who is lenient when one cannot get another cup. Even so, in practice, this requires investigation. Mishbetzos Zahav disqualifies even if it holds a Revi'is below the hole. Eliyahu Rabah disqualifies even a tiny nick in the brim, unless there is no other cup. According to the Mishnah Berurah, we need not say all this, for Shalem is only l'Chatchilah. Shirei Keneses ha'Gedolah brings an argument about whether 'one must pursue' is Me'akev. It connotes that it is not Me'akev, but in Siman 219:3 (one must bless ha'Gomel in front of 10), 'one must' is Me'akev. If only the base is broken, surely this is not Me'akev due to not being Shalem. Even if 'one must' is Me'akev, there are other Perushim of 'Chai', and the Tur said that it is good to fulfill all the Perushim. Surely this connotes l'Chatchilah. However, some Poskim say that it is Me'akev, like Kaf ha'Chayim brings.

Minchas Yitzchak (DH ul'Halachah): A paper cup is worse than a Kli with a broken base. I agree with Igros Moshe, but for a different reason, like I explained (Minchas Yitzchak 3:76, and elsewhere). If a Nochri made a disposable baking pan to be used once, must it be immersed? The Rambam says that a horn that one uses once and discards is not Mekabel Tum'ah. This is because a Kli is only what is used constantly. Some say that Tevilah is different. Gedulei Taharah says that people do not immerse pots (of Nochrim) in which whiskey is cooked, for experts say that if one leaves whiskey in them for a while, it will spoil. If so, it is not a Kli of usage. Temporary usage requires Tevilah only if it could be used regularly. Grupiyos of olives are not Mekabel Tum'ah because they are Memarin (Kelim 12:8). The Ra'avad explains that they give a bitter taste to the olives. We are Metaher a Kli that stands to be discarded, e.g. one must break it to open it (Kelim 16:5, Rambam Hilchos Kelim 5:7). Chelkas Yakov (YD 46) says that even though one could reuse disposable Kelim, since it is not normal to do so, they are not Mekabel Tum'ah and one need not immerse them.

Minchas Yitzchak (DH u'Mimeila): Seemingly, similarly it is not a Kli regarding Kidush. However, if one has no other cup, one can designate a disposable cup for fixed use, and then use it for Kidush. The Rambam said that a horn is not Mekabel Tum'ah, but if he intended (to reuse it), it is Mekabel Tum'ah. Zemiros Shabbos (of the Satmar Rav) and Sharga ha'Me'ir were stringent not to use a paper cup for Kidush. I agree. Klei Gelalim are Kosher even for Netilas Yadayim, which is more stringent than Kidush, even though they are not Mekabel Tum'ah, and they are not important. However, something that one does not intend to reuse is not considered a Kli.

Va'Ya'an Yosef (OC 65): Sharga ha'Me'ir is stringent about using a paper cup for Netilas Yadayim. A bag or box is Pasul may not be used. Rashi explains that they are not made to hold water. I.e. they have holes. If one plastered them to hold water, Batlah Daito Etzel Kol Adam (it has no effect, because) most people do not do so. Paper cups are made to hold liquids. The Yam Shel Shlomo (Chulin 8:32) requires an important Kli. He does not mean that it is not made of something cheap, rather, that its use is important. (Therefore, one may use them.)

Tzitz Eliezer (12:23): I see no reason to forbid using disposable cups for Kidush or Havdalah. A cup with a base was made to rest on its base. If the base broke, this is not Chai. The Rambam says that a horn is Tahor, for nothing shows that it was made to be a Kli. Even so, with intent it is Mekabel Tum'ah. Paper cups are made to be used. The Rambam says that even Kelim of paper are Mekabel Tum'ah.