Solvents

• Petroleum-based compounds are widely used in dry cleaning applications. Petroleum solvents have the disadvantage of being attractive to bacteria, which can produce sour smells. Bactericides or antioxidants are sometimes added to combat this. Perchloroethylene (PCE) has been used as a dry cleaning solvent in the United States since 1934. Approximately 86.7 percent of dry cleaners in the United States were using PCE in 1980. However, regulations regarding PCE emissions have led to a decline in its use. Approximately 70 percent of dry cleaning operations in the United States were still using PCE in 2007.
  
  Glycol ethers such as Rynex and Impress are also used in dry cleaning. Other dry cleaning solvents include those based on silicon and n-propyl bromide. Liquid carbon dioxide under extremely high pressure is also sometimes used.
  
  

Detergents

• Detergents are used in dry cleaning to help remove dirt, suspend the dirt after it has been removed and to penetrate the fabric so solvents can remove any stains. Dry cleaning detergents have historically included paste, gel and liquid soaps. These started to lose ground by the 1950s in favor of synthetic detergents. Synthetic detergents are usually made of surfactants, chemicals that lower a liquid's surface tension, and solvents.
  
  

Sizing

• Sizing is a chemical added to some fabrics during the manufacturing process to give the fabric shape and texture. Sizing can be washed away when the fabric is cleaned, and is used in the dry cleaning process as a restorative measure. Sizing used in dry cleaning is made of hydrocarbon resins, and is available in both solid and liquid forms. Sizing is applied in dry cleaning by adding it to the dry cleaning machine, by dipping the clothing in it, or as an aerosol spray.
  
  

Other Chemicals

• Optical brighteners, fabric conditioners and anti-static/anti-lint agents are sometimes added to the dry cleaning process. Optical brighteners are used to brighten white garments and are usually added to detergents or sizing. Fabric conditioners are used to restore the appearance of leather, silk and suede. Sulfonated polystyrene or sulfonated polystyrene/maleic anhydride polymers are used to prevent static and lint.
  
  

Precleaning Chemicals

• Precleaning chemicals are used to treat clothing with heavy stains. Stains that remain on clothing after dry cleaning are treated with the same chemicals. There are three kinds of precleaning chemicals: bleaches, wet-side agents and dry-side agents. Bleaches are only used when other cleaning methods have failed. Wet-side agents are used to remove stains that are water soluble. They are subdivided into alkaline, acidic and neutral depending on their pH level. Dry-side agents are used to clean oily stains such as those left by wax and grease. They are primarily made of alcohol and solvents.