'Coals' in the Bible

Now, in the midst of the living beings there was something that appeared to glow like coals kindled by a fire, like torches that moved back and forth between the living beings. The fire was dazzling, and lightning flashed from the fire.

The LORD spoke to the man who was clothed in white linen, telling him, "Go between the whirling wheels, under the cherubim, and fill your hands with burning coals from among the cherubim. Then scatter them over the city." So he entered as I watched.

Make the pot stand empty on the coals until its bronze glows red, its rust can be scoured off, and its dross completely removed.