Rumford’s Radiant Idea
Count Rumford’s fireplace design, taller than earlier conventions, was also shallower, with widely angled covings to better reflect and radiate heat. He advocated plastering and whitewashing the firebox to keep it clean and reflective. Modern physicists argue that what really happens is that, whitewashed or not, the firebox absorbs heat and re-radiates it out into the room. There isn’t a significant difference in performance between whitewashed plaster and soot-covered brick.