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Issue 974

DRY CLEANING

• Dry cleaning was a result of an accident that happened in France in 1828 when a maid tipped over a kerosene lamp on a dirty tablecloth. When the kerosene dried, that spot on the tablecloth was clean. Her employer, Jean-Baptiste Jolly, was intrigued and submerged the entire tablecloth in a tub of kerosene. The result was a clean tablecloth and a new industry. The business called Jolly-Belin in Paris is credited as the first dry cleaning business, using kerosene as its primary cleaning material.

• Yet, Jolly wasn’t the first to figure out how to clean clothing without water. In 1821, a tailor in New York City named Thomas Jennings was granted a U.S. patent for the process. As a tailor, he heard his customers complain over and over again that their fine and fancy garments would not hold up to the rigors of the wash board. Jennings patented a process he called “dry scouring” using solvents instead of water. Jennings was African American, in a day and age where the rights any patents granted to slaves were automatically handed over to their owners. However, Jennings was a free man. He used the money he earned from his dry cleaning process to buy his wife and children out of slavery, and he also funded many abolitionist organizations. We don’t know which solvent he used in his process due to a fire that destroyed the patent records in 1836.

• Solvents used in the early days of dry cleaning include turpentine, kerosene, benzene, and gasoline. These are all extremely flammable, often resulting in fires and explosions. Dry cleaning businesses were often banned from operating inside city limits for this reason. Benzene was toxic when inhaled by workers. Turpentine smelled bad if residue was left on clothes.

DRY CLEANING

• Around 1900, scientists developed chlorinated hydrocarbons, which are nonflammable solvents. The result was perchloroethylene, shortened to “perc,” a chlorinated hydrocarbon that happens to remove stains by dissolving organic materials.

• Perc was first synthesized by British chemist and physicist Michael Faraday in 1821. It became the top choice of dry cleaners in the 1930s.

• Perchloroethylene is very stable and non-flammable. It’s used as a de-greaser in the metal industry, to clean photographic negatives, and can be found in paint strippers, spot removers, neutrino detectors, refrigerants, and has been used to treat hookworm.

• Dry cleaning isn’t really dry; it’s just that instead of being washed in water, the clothing is washed in solvents instead. They are washed in what looks very much like a normal front-loading washer, the difference being that both the washing and the drying are done in the same machine. After the wash and spin cycle, the solvent is collected in order to be distilled and re-used. As the dryer shoots jets of hot air into the wet clothing, the fumes are caught and the solvent condensed so that few fumes enter the environment. Dry cleaners are therefore able to re-use their chemicals over and over again, recapturing about 99.99% of the perc that is used. By the time the clothing is dry, all the solvent has evaporated and no odor or residue remains.

• The busiest time of year for dry cleaners is April through June, while January and February are traditionally the slowest months of business.