Covering the Sefer Torah

Question: I sometimes stand next to the bimah to help out during leining though am confused as to when to cover the sefer Torah. Should it be covered after every aliya?

Answer: The Gemara (Shabbos 5b; Eruvin 98a) teaches that if a sefer unrolled on Shabbos into a reshus hayachid in a way that they could not roll it back, they should turn it over so that the writing should not be exposed.

The Shulchan Aruch (YD 277:1) writes that a sofer should cover the sefer Torah when leaving it to dry, rather than turn it over, as covering it is more respectful. The Bach (YD 277:1) explains that we learn from here that it is disrespectful to leave a sefer Torah or other sefarim open for any extended period of time (See Shach YD 277:1; Baer Heitev YD 277:1; Aruch Hashulchan YD 277:2).

Thus, the Shulchan Aruch (OC 139:5) writes that the minhag is to cover the sefer Torah between each aliya. The Rema, however, writes that the minhag Ashkenaz is to roll it closed. Likewise, the Baer Heitev (OC 139:8) and Mishna Berura (139:21) quote the Taz that one should not cover the sefer Torah each time as it is a tircha, extra bother. However, it is appropriate to cover the sefer Torah when saying kaddish afterwards. Thus, we cover the sefer Torah whenever there is a substantial pause, such as the gabbai saying mi shebeirach.

In conclusion, one should close, but not cover the sefer Torah after an aliya. When there is a longer break, such as kaddish or mi shebeirach being recited, then it should be covered.