The Materials of a Tzitzis Garment
Question: Can the tzitzis garment be made of any material?
Discussion: Garments of any material require tzitzis, and one can fulfill the mitzvah with them (with certain exceptions; see below). However, there is a dispute as to whether the Biblical mitzvah indeed includes all materials, or is limited to garments of wool and linen, with the mitzvah of tzitzis for other materials being rabbinic. The relevance of this is that, given the option, one should certainly prefer to perform the mitzvah on the Biblical level rather than on the rabbinic level. Now, Rema (9:1) rules according to the opinion that all materials require tzitzis by Torah law. Yet, Mishnah Berurah (9:5) writes that the meticulous should make a point of having both a tallis gadol and a tallis kattan of wool, in order to fulfill the mitzvah on the Torah level according to all opinions.165
However, many great Rabbanim did wear a tallis kattan of cotton, contrary to the ruling of Mishnah Berurah.166 In hotter temperatures, where wearing a tallis kattan of wool may be too uncomfortable, it is certainly acceptable to wear a tallis kattan made of cotton.
Question: Can a tallis kattan be made of synthetic material?
Discussion: Some materials do not require tzitzis even rabbinically. Namely, materials that are made into garments without being woven. Such garments do not meet the halachic definition of a “garment” at all.167 The most prominent example is leather. Since leather is generally not woven, leather garments are entirely exempt from tzitzis168 (that is, even in an instance where it actually was woven; see further).
Some maintain that synthetic materials, likewise, do not meet the halachic definition of a “garment.”169 Their reasoning is based on the point made above that, even if pieces of leather are woven together into a garment, it does not require tzitzis170 – in their view, this is because leather can be made in to a garment without weaving. Therefore, since a synthetic material can be fashioned into a garment without being woven, garments made of such materials are categorically exempt from the mitzvah of tzitzis. Yet others disagree.171 They argue that a leather garment is not exempt because it can be made into a garment without weaving, but rather because it usually is not woven. Synthetic garments, however, usually are woven, so they do require tzitzis.
Since there are different views on the issue, if one has a four-cornered garment made of a synthetic material, he should not wear it without tzitzis (even if the fibers are not woven172), but on the other hand, he should not recite a berachah upon wearing it. Due to the questionable nature of synthetic materials in this regard, a tallis kattan should ideally not be made of synthetic material.
165 Essentially, linen would be equally acceptable (with tzitzis strings made of linen), yet the halachah is not to wear a four cornered garment made of linen at all; see Shulchan Aruch 9:6.
166 This was the practice of the Vilna Gaon (Ma’aseh Rav 17), R’ Chaim Soloveitchik (Harav Mibrisk IV, p. 388), Chazon Ish (Shoneh Halachos 9:1; Orchos Rabbeinu I, p. 19) and the Steipler Gaon (Orchos Rabbeinu ibid.). See Sefer Tzitzis, Chapter 9, fn. 26, which suggests several explanations for this practice.
167 See Levush 10:4; and see Aruch Hashulchan 10:9.
168 Shulchan Aruch 10:4. Mishnah Berurah 10:11 and Chazon Ish (3:33) state explicitly that they do not require tzitzis even by rabbinic law.
169 Igros Moshe, Orach Chaim II, 1.
170 See commentary of R’ Ovadia of Bartenura and Rash to Keilim 27:1
171 Teshuvos Vehanhagos I:34; Az Nidberu VII:52-53. Har Tzvi 1:9; Halichos Shlomo, Tefillah 3:16. Igros Moshe himself (ibid.) initially suggests that synthetic fibers are different from leather since they are first produced as fibers. However, he dismisses this argument (but see Az Nidberu ibid.).
172 See Az Nidberu (ibid.).