Dry cleaning is a cleaning process that uses a chemical solvent in place of water. The solvent is usually tetrachloroethylene (perchloroethylene; known as “perc”). A dry cleaning machine is similar to a combination of a washing machine and dryer. Garments are put into a washing chamber known as a drum or basket. The washing chamber consists of this perforated drum that is then surrounded by solvent in an outer shell.
The chamber is filled about 1/3 full of solvent at 30 degrees Celsius (86 degrees Fahrenheit) and then rotated. During the wash cycle, the solvent is passed through a filtration chamber and then returns to continue washing the garments. Next, the solvent is removed and distilled using a boiler and condenser. It is here that any remaining water is separated out. The “clean” solvent is then kept in a separate tank.
At the end of the wash cycle, the garments are rinsed with fresh distilled solvent. Then the dry cleaning solvent is extracted for reuse. Most solvent is spun free of the fabric. To dry the garments, they are tumbled in a stream of warm air, evaporating traces of the leftover solvent.
After drying is complete, a deodorizing (aeration) cycle cools the clothes and circulates cool outside air over the garments and then through a vapor recovery filter consisting of activated carbon and polymer resins. Now the garments are clean and ready for the finishing touches! A typical wash cycle lasts 8 to 15 minutes.
Natural fibres, such as wool, cotton, and silk should not be left dirty for a long time, since they are unlikely to be restored to their original colour and finish.