Dry Cleaning

Dry cleaning is any cleaning process for clothing and textiles using a solvent other than water. Dry cleaning still involves liquid, but clothes are instead soaked in a water-free liquid solvent, tetrachloroethylene, known in the industry as "perc", which is the most widely used solvent. Alternative solvents are 1-bromopropane and petroleum spirits. Most natural fibers can be washed in water but some synthetics react poorly with water and must be dry-cleaned.

History
Dry cleaning originated with American tailor, abolitionist and entrepreneur Thomas L. Jennings, who became the first Black patent-holder for his invention in 1821. Jennings referred to his method as “dry scouring”. French dye-works operator Jean Baptiste Jolly developed his own method using kerosene and gasoline to clean fabrics. He opened the first dry-cleaners in Paris in 1845.

Flammability concerns led William Joseph Stoddard, a dry cleaner from Atlanta, to develop Stoddard solvent as a slightly less flammable alternative to gasoline-based solvents. The use of highly flammable petroleum solvents caused many fires and explosions, resulting in government regulation of dry cleaners. After World War I, dry cleaners began using chlorinated solvents. These solvents were much less flammable than petroleum solvents and had improved cleaning power.

Infrastructure
Dry cleaning businesses, from the perspective of the customer, are either plants or drop shops. A plant does on-site cleaning. A drop shop receives garments from customers, sends them to a large plant, and then has the cleaned garment returned to the shop for collection by the customer. The turnaround time is longer for a drop shop than for a local plant. However, running a plant requires more work for the business owner. Since 2010, in some markets, web apps have been used to schedule low-cost home delivery for dry cleaning.

This cycle minimized the risk of fire or dangerous fumes created by the cleaning process. At this time, dry cleaning was carried out in two different machines—one for the cleaning process, and the second to remove the solvent from the garments.

Mechanism
In terms of mechanism, dry cleaning selectively solubilizes stains on the article. The solvents are non-polar and tend to selectively extract compounds that cause stains. These stains would otherwise only dissolve in aqueous detergents mixtures at high temperatures, potentially damaging delicate fabrics.

Non-polar solvents are also good for some fabrics, especially natural fabrics, as the solvent does not interact with any polar groups within the fabric. Water binds to these polar groups which results in the swelling and stretching of proteins within fibers during laundering. Also, the binding of water molecules interferes with weak attractions within the fiber, resulting in the loss of the fiber's original shape. After the laundry cycle, water molecules will dry off. However, the original shape of the fibers has already been distorted and this commonly results in shrinkage. Non-polar solvents prevent this interaction, protecting more delicate fabrics.

Symbols
The international GINETEX laundry symbol for dry cleaning is a circle. It may have the letter P inside it to indicate perchloroethylene solvent, or the letter F to indicate a flammable solvent. A bar underneath the circle indicates that only mild cleaning processes is recommended. A crossed-out empty circle indicates that dry cleaning is not permitted.