Dry cleaning is a process that uses non-water-based solvents to clean garments. Clothes are placed into a machine resembling a large washer, and the chamber is partially filled with a powerful solvent. The machine agitates the clothing while the solvent breaks down stains and residue. The cleaning chamber spins at high speeds to extract the remaining solvent and aerate the clothing, rendering it clean and fresh.
Originally, the dry cleaning process used hydrocarbon-based solvents, such as kerosene. These were much more effective at removing grime than detergents of the time, but the flammable nature of these chemicals led to fires and explosions. By the 20th century, most dry cleaners switched to chlorinated solvents, with perchloroethylene, or perc, becoming the industry standard. Originally, excess solvent was vented to the outside air during the cleaning process, but its potential toxicity led to regulations that required the capture and reuse of the solvent.
The powerful substances used in dry cleaning not only break down stains and grime, but even small objects and fragile stitching. For instance, if a pen is left in the pocket of a garment undergoing dry cleaning, it may melt and leave plastic residue all over the clothing and the machine. Buttons and fasteners may also not survive the cleaning process, and are often removed before cleaning.