In 1779, Richard Dearman was granted an English patent on a new method of making mills for grinding coffee. In 1798, the first American patent on an improved coffee grinding mill was granted to Thomas Bruff, Sr. It was a wall mill, fitted with iron plates, in which the coffee was ground between two circular nuts, three inches broad and having coarse teeth around their centers and fine shallow teeth at the edges.
De Belloy's (or Du Belloy's) coffee pot appeared in Paris about 1800. It was first made of tin; but later, of porcelain and silver—the original French drip pot. This device was never patented; but it appears to have furnished the inspiration for many inventors in France, England, and the United States. The first French patent on a coffee maker was granted to Denobe, Henrion, and Rouch in 1802. It was for a "pharmacological-chemical coffee-making device by infusion." Charles Wyatt obtained a patent the same year in London on an apparatus for distilling coffee.
In 1806, Hadrot was granted a French patent on a device "for filtering coffee without boiling and bathed in air." This use of the word filtering was misleading, as it was many times after in French, English, and American patent nomenclature, where it often meant percolation or something quite different from filtration. True percolation means to drip through fine interstices of china or metal. Filtration means to drip through a porous substance, usually cloth or paper. De Belloy's pot was a percolator. So was Hadrot's. The improvement on which Hadrot got his patent was to "replace the white iron filter (sic) used in ordinary filtering pots by a filter composed of hard tin and bismuth" and to use "a rammer of the same metal, pierced with holes." The rammer was designed to press down and to smooth out the powdered coffee in an even and uniform fashion. "It also," says Hadrot in his specification, "stops the derangement which boiling water poured from a height can produce. It is held by its stem a half inch from the surface of the powder so that it receives only the action of the water which it divides and facilitates thus the extraction which it must produce in each of the particles."
A coffee percolator was invented in Paris about 1806 by Benjamin Thompson, F.R.S., an American-British scientist, philanthropist, and administrator. He was known as Count Rumford, a title bestowed on him by the Pope. Rumford's invention was first given to the public in London in 1812. He has gained great credit for his device, because of an elaborate essay that he wrote on it in Paris under the title of "The excellent qualities of coffee and the art of making it in the highest perfection", and that he caused to be published in London in 1812. It was a simple percolator pot provided with a hot-water jacket, and was a real improvement on the French drip or percolator coffee pot invented by De Belloy, but not at all unlike Hadrot's patented device. Count Rumford, however, was a picturesque character, and a good advertiser. He is generally credited with the invention of the coffee percolator; but examination of his device shows that, strictly speaking, the De Belloy pot was just as much a percolator, and apparently antedated it by about six years.
De Belloy employed the principle of having the boiling water drip through the ground coffee when held in suspension by a perforated metal or porcelain grid. This is true percolation. Hadrot did the same thing with the improvements noted above. Count Rumford in his essay admits that this method of making coffee was not new, but claims his improvement was. This was to provide a rammer for compressing the ground coffee in the upper or percolating device into a definite thickness, this being accomplished by providing the perforated circular tin disk water-spreader that rested on the ground coffee with four projections, or feet, that kept the spreader within half an inch of the grid holding the powder in suspension and free from "agitation."
His argument was that two-thirds of an inch of ground coffee should be leveled and compressed into a half-inch thickness before the boiling water was introduced. Practically the same result was achieved in the De Belloy and Hadrot pots, also provided with water-spreaders and pluggers, but the same mathematical exactitude in the matter of the depth of the ground coffee before the percolation started was not assured. De Belloy's spreader did not have the projections on the under side upon which Count Rumford laid such stress. Then there was the hot-water jacket, which was an improvement on Hadrot's hot air bath. Inventors that followed Rumford have made light of the importance that he attached to scientific accuracy in coffee-making; but it is interesting to note how many of the features of the De Belloy, Hadrot, and Rumford pots have been retained in the modern complex coffee machines, and in most of the filtration devices.