Dry cleaning is wet after all, just with a liquid that isn't water
Dry-cleaned clothes do get soaked, only in an organic solvent rather than water. The trade supposedly began after a French dye-works owner noticed in 1825 that lamp oil spilled on his tablecloth had left it cleaner. Two decades later Jean Baptiste Jolly opened the first dry-cleaning service in Paris.
Water is a polar liquid, and it latches onto polar groups in fibres, such as the hydroxyls in cellulose, making them swell and stretch. That is why viscose, silk and acetate can warp, fade or weaken in a normal wash. Non-polar solvents leave those groups alone while still dissolving many greasy stains that water would only shift at temperatures hot enough to harm delicate cloth.
The early solvents were alarming: kerosene, gasoline and benzene compounds, which caused so many fires and explosions that governments began regulating cleaners. In 1924 William Joseph Stoddard, an Atlanta dry cleaner, developed the slightly safer white spirit that still bears his name. After the First World War, chlorinated solvents that barely burned took over, and in 1930 Dow Chemical chemists Sylvia Stoesser, John Grebe and J. Lawrence Amos proposed perchloroethylene, testing it in a lab washer whose rubber parts they swapped for neoprene. By 1933 perc was being hailed as the ideal solvent, and it still ran an estimated 50% to 70% of American cleaners in 2012.
A modern machine is essentially a washer and dryer in one sealed box. The drum fills about one-third with solvent and turns for 3 to 15 minutes; hydrocarbon solvents need at least 25 because they dissolve grime more slowly. A rinse in freshly distilled solvent stops dirt settling back, then the drum spins and warm air at about 60 to 63 degrees Celsius evaporates what remains. Chilled coils condense the vapour for reuse, and today's machines recover over 90% of their solvent.
Early machines simply vented fumes outdoors. Later generations captured and filtered vapour, and the newest will not unlock the door until solvent in the chamber air drops below 300 parts per million.
Source: Dry cleaning
