Question: As I was putting my tefillin away, I noticed that there are some spots on my retzuos (straps) where the black paint has come off. Are they kosher or do I need to paint them before wearing them again?
Answer: The Gemara (Menachos 35a) writes that there is a halacha lemoshe misinai that retzuos need to be (painted) black. According to the Elya Rabba (32:62) black is unique as any colour painted on top gets absorbed into it. Thus, black symbolises the oneness of Hashem.
The Shulchan Aruch (OC 33:3) writes that only the side that shows needs to be painted black. Recently, many have bought straps that are painted black on both sides, though R’ Shmuel Wosner (Shevet Halevi 9:16) writes that as the majority of poskim wrote that this isn’t necessary, there is no reason to do so.
The Mishna Berura (33:19) writes that one must pay particular attention to the kesher (knot) on the shel yad as that it is likely to get worn. So long as the retzuos look black at first glance they are kosher, however, even if on closer inspection they are grey or blue (Biur Halacha 33:3).
The Chafetz Chaim (Biur Halacha 33:3) writes that he isn’t sure as to whether the entire retzuos need to be black or just the minimum amount of the retzuos necessary to be kosher (See Shulchan Aruch OC 27:8).
Most poskim (Maharshag OC 1:7; Salmas Chaim 40; Halichos Shlomo, Tefilla 4:28; Teshuvos Vehanhagos 2:22) maintain that so long as most of the straps are black, they are kosher.In conclusion, one should paint over any white spots, especially if they are closer to the kesher and within the ‘minimum size’. When painting the straps, one should say leshem kedushas tefillin (Rema OC 33:4) and do so with ink made from kosher ingredients.