Dry Cleaning Process


Dry cleaning is any cleaning process for clothing and textiles using a chemical solvent other than water. The solvent used is typically tetrachloroethylene (perchloroethylene), abbreviated “perc” in the industry and “dry-cleaning fluid” by the public. It is often used instead of hand washing delicate fabrics, which can be excessively laborious.

Dry Cleaned, Clean Clothes

A dry-cleaning machine is similar to a combination of a domestic washing machine, and clothes dryer. Garments are placed into a washing/extraction chamber (referred to as the basket, or drum), which is the core of the machine.

During the wash cycle, the chamber is filled approximately one-third full of solvent and begins to rotate, agitating the clothing. The solvent temperature is maintained at 30 degrees Celsius (86 degrees Fahrenheit), as a higher temperature may damage it. The solvent is then removed and sent to a distillation unit comprising a boiler and condenser. The condensed solvent is fed into a separator unit where any remaining water is separated from the solvent and then fed into the ‘clean solvent’ tank.

Garments are also checked for foreign objects. Items such as plastic pens will dissolve in the solvent bath and may damage textiles beyond recovery. Some textile dyes are “loose” (red being the main culprit), and will shed dye during solvent immersion. These will not be included in a load along with lighter-color textiles to avoid color transfer. Many decorative fasteners either are not solvent proof or will not withstand the mechanical action of cleaning. These will be removed and restitched after the cleaning, or protected with a small padded protector. Fragile items, such as feather bedspreads or tasseled rugs or hangings, may be enclosed in a loose mesh bag.

Many people believe that marks or stains can be removed by dry cleaning. Not every stain can be cleaned just by dry cleaning. Some need to be treated with spotting solvents—sometimes by steam jet or by soaking in special stain-remover liquids—before garments are washed or dry cleaned. Also, garments stored in soiled condition for a long time are difficult to bring back to their original color and texture. Natural fibers such as wool, cotton, and silk of lighter colors should not be left in dirty or soiled condition for long amounts of time as they absorb dirt in their texture and are unlikely to be restored to their original color and finish.

At the end of the wash cycle, the machine starts a rinse cycle wherein the garment load is rinsed with fresh distilled solvent from the pure solvent tank. This pure solvent rinse prevents discoloration caused by soil particles being absorbed back onto the garment surface from the “dirty” working solvent.
After the rinse cycle, the machine begins the extraction process, which recovers the solvent for reuse. Modern machines recover approximately 99.99% of the solvent employed.

During the drying cycle, the garments are tumbled in a stream of warm air (60-63°C/140-145°F) that circulates through the basket, evaporating any traces of solvent left after the spin cycle. The air temperature is controlled to prevent heat damage to the garments.

The exhausted warm air from the machine then passes through a chiller unit where solvent vapors are condensed and returned to the distilled solvent tank. Modern dry cleaning machines use a closed-loop system in which the chilled air is reheated and recirculated.

This results in high solvent recovery rates and reduced air pollution. After the drying cycle is complete, a deodorizing (aeration) cycle cools the garments and removes the last traces of solvent, After the aeration cycle, the garments are clean and ready for pressing/finishing.