Benjamin Thompson- Lord Rumford

The Rumford Fireplace

When Lord Rumford was not chasing skirts, he put his brilliant mind to work solving practical problems in the world. This was a common attribute of many of the  settlers of America in the 18th century and brings to mind other “Renaissance men” such as Benjamin Franklin and Thomas Jefferson.  If you have lived in New England for awhile, you have probably heard of the “Rumford” fireplace, but might not have understood why it was such an advance in woodburning technology.

A plan of a traditional fireplace next to the Rumford design.

“Rumford applied his knowledge of heat to the improvement of fireplaces in the 1790s. He made them smaller and shallower with widely angled covings so they would radiate better. And he streamlined the throat, or in his words “rounded off the breast” so as to “remove those local hindrances which forcibly prevent the smoke from following its natural tendency to go up the chimney…” Rumford wrote two papers detailing his improvements on fireplaces in 1796 and 1798. He was well known and widely read in his lifetime and almost immediately in the 1790s his “Rumford fireplace” became state-of-the-art worldwide. Subsequent testing of Rumford’s designs has shown that their efficiency would qualify them as clean-burning stoves.” The Rumford fireplace created a sensation in London when he introduced the idea of restricting the chimney opening to increase the up draught. He and his workers changed fireplaces by inserting bricks into the hearth to make the side walls angled, and they added a choke to the chimney to create a circulation of air inside the chimney. In the unmodified chimney, smoke rises up the chimney propelled only by buoyancy…Thompson became a celebrity when news of his success became widespread. In an age when fires were the principal source of heat, this simple alteration in the design of fireplaces was copied widely… Rumford fireplaces were common from 1796, when Count Rumford first wrote about them, until about 1850. Jefferson had them built at Monticello, and Thoreau listed them among the modern conveniences that everyone took for granted.” Wikipedia

A cross section of a traditional fireplace next to the Rumford design.

“The work for which Rumford is perhaps best known today is his energy-efficient design for fireplaces. His essay “Chimney Fireplaces, with Proposals for Improving them to Save Fuel; to Render Dwelling-houses more Comfortable and Salubrious, and Effectually to prevent Chimneys from Smoking” was first published in 1796, in the Bibliotheque Britannique in Geneva, and in volume I of his Essays, Political, Economical and Philosophical, published in London. An American edition of the Essays was published in 1798…A Rumford-design fireplace in the South Square Room…Thomas Jefferson owned volume I (Boston, 1798) and volume II (1799) of the three-volume American edition of Rumford’s Essays. However, it seems that Jefferson was familiar with Rumford’s designs well before 1798. Jefferson’s remodeling notes for Monticello, begun in November of 1796, contain sketches and notes for ‘Count Rumford’s fire places in the square rooms;’ ….By 1798 Rumford was already complaining that masons took short cuts and ‘neglected to round the breast,’ and his second essay on fireplaces published in that year was written primarily to address these faults. Once again he re-emphasized the importance of keeping the ‘back perfectly straight’ and of ‘rounding the breast.’” (The Collected Works of Count Rumford; Harvard Press; 1969; vol. 2.) Jim Buckley, rumford.com