617. Fuels Prohibited for Shabbos Lamps

Shabbos 5:8

The fuel for the Shabbos lamp must draw after the wick. Fuel that does not draw after the wick may not be used. Examples include tar, beeswax, oil from a gourd, fat from a sheep tail and tallow. We may not light Shabbos lights using wicks that do not catch well and fuels that do not draw after the wick as a preventive measure against the possibility that one may come to tilt a dim lamp in order to improve its light.

Shabbos 5:9

One may light with tallow or with boiled fish innards if they have been mixed with a little oil. Other prohibited fuels may not be used even if they are mixed with permitted fuels because they still don’t draw.