Q. What substances may be used for Shabbat lights?
A. In contrast to the Catholic Church which uses a spiritual criterion, requiring 51% of beeswax in candles used in its services as beeswax is seen as symbolising purity, Jewish law is concerned with practical issues.
Materials with a bad smell may not be used, as they might force people to leave the room, affecting the peace and joy of Shabbat. The wick must not be too hard or coarse to suck up the liquid fuel (Talmud Shabbat 20b/21a; Shulchan Aruch, Orach Chayyim 264).