I was binge watching old Mythbusters shows so I could clear them of my DVR and a thought struck me. There is a theory that the Baghdad Battery was used to provide electricity to some form of light bulb in Ancient Egypt so when the artwork in tombs was created [first the tomb was dug into the rock, then the walls plastered and carved with images, then painted in bright colors] the artisans did not leave soot deposits on the ceiling.
It is perfectly possible to create the tomb and leave it without soot deposits without electricity. First the tunnelers create the tomb, and the plasterers lay in the walls. The artists work along with the plasterers to create the bas relief artwork, and the last step of decoration starts at the remote back end of the tomb, and the artists paint their way out - just like you do when you are painting the floor of a room. Fresh clear colorful walls and ceiling, and no soot. The priests and slaves tuck in the dead guy and grave goods, close it up and hope nobody robs the tomb for the goodies inside.