Dry cleaning (or dry-cleaning) is any cleaning process for clothing and textiles using a solvent (a liquid or gas that can dissolve some materials) without water. The solvent used is usually tetrachloroethylene (perchloroethylene) which is very strong and can dissolve oils. The solvent is called "perc" in the industry and "dry-cleaning fluid" by the public. It is often used instead of hand washing delicate fabrics that cannot be washed by water because water would damage them. People use dry cleaning because it takes less work than hand washing.
History
The ancient Romans used a chemical called ammonia (derived from urine) and fuller's earth (a clay that can absorb grease and oil.) to clean their woolen clothes. Such laundries were very famous, with at least one in every town of any notability, and frequently the largest employer in a district. These laundries got their urine from farm animals, or from special pots situated at public bathrooms. The workforce made so much money that fuller's guilds (a group that works in solely one job, in this case, making fuller's earth, this special clay) were an important political force. Also, the government taxed the collection of urine and sent people to jail for wetting their pants.
Modern dry cleaning uses solvents that do not use water to remove dirt and stains from clothing. Jean Baptiste Jolly discovered that petroleum-based solvents (chemicals like gasoline or kerosene) can be used for dry-cleaning in the mid-19th century. Jolly was a French dye-works owner. He noticed that his tablecloth became cleaner after his maid spilled kerosene on it. Because of this, he developed a service cleaning people's clothes this way, which became known as "nettoyage à sec" or "dry cleaning".
Early dry cleaners used petroleum-based solvents, such as gasoline (petrol) and kerosene. Fire 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 government started to control dry cleaners because the highly flammable petroleum solvents caused many fires and explosions.
After World War I, dry cleaners began using chlorinated solvents. These solvents were much less flammable than petroleum solvents and were more powerful. By the mid-1930s, the dry cleaning industry had adopted tetrachloroethylene (perchloroethylene), widely called "perc", as the best solvent. It has excellent cleaning power and is stable, nonflammable, and gentle to most clothing. Some dry cleaners use different chemicals.
Traditionally, the actual cleaning process was carried out at centralized "factories"; high street cleaners shops received garments from customers, sent them to the factory, and then had them returned to the shop after being cleaned, where the customer could collect them. This was due mainly to 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 itself and the second to dry the clothing.
Machines of this era were called vented; their fumes and drying exhausts were sent into the air, in the same way as with modern tumble dryer exhausts. This added to environmental contamination. Also much potentially reusable perc was lost to the atmosphere. Much stricter controls on solvent emissions have ensured that all dry cleaning machines in the western world are now fully enclosed. No solvent fumes are vented to the atmosphere. In enclosed machines, solvent recovered during the drying process is returned condensed and distilled. So, it can be reused to clean more clothes, or safely thrown away. The majority of modern enclosed machines also incorporate a computer-controlled drying sensor, which automatically feels when most traces of perc have been removed from the load during the drying process. This system ensures that only the smallest amount of perc fumes will be released when opening the door at the end of the cycle.
Process
A dry-cleaning machine is similar to a combination of a domestic washing machine, and clothes dryer. Garments are placed into a washing chamber (referred to as the basket, or drum). The chamber is the core of the machine. The washing chamber contains a horizontal, perforated drum that rotates within an outer shell. The shell holds the solvent while the rotating drum holds the clothing. The basket can hold between about 10 and 40 kg (20 to 80 lb).