4. Boil, seethe, simmer, stew are used figuratively to refer to agitated states of emotion. To boil suggests the state of being very hot with anger or rage: Rage made his blood boil. To seethe is to be deeply stirred, violently agitated, or greatly excited: A mind seething with conflicting ideas. To simmer means to be on the point of bursting out or boiling over: to simmer with curiosity, with anger. To stew is to worry, to be in a restless state of anxiety and excitement: to stew about ( or over ) one's troubles.

Did you mean boil down?