refine

The dawn of the oil age was fairly recent. Although the stuff was used to waterproof boats in the Middle East 6,000 years ago, extracting it in earnest began only in 1859 after an oil strike in Pennsylvania.[…]It was used to make kerosene, the main fuel for artificial lighting after overfishing led to a shortage of whale blubber. Other liquids produced in the refining process, too unstable or smoky for lamplight, were burned or dumped.

to refine someone's manners

My dear Harriet, you must not refine too much upon this charade.—You will betray your feelings improperly, if you are too conscious and too quick, and appear to affix more meaning, or even quite all the meaning which may be affixed to it.

to refine thought