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Dry Cleaning?
Dry cleaning is not actually a "dry" process, as its name would suggest. In actuality, the
dry cleaning process is not that unlike the normal laundry that we do at home. In each
process, dirty clothes are placed in contact with a solvent that removes the dirt and stain.
With regular laundry, water is the solvent with an added detergent to facilitate the
cleaning process. In dry cleaning processes, the clothing is washed with a liquid
solvent other than water. The solvent is one of several different organic-based chemicals.
Dry cleaning is only referred to as "dry" cleaning because the washing process is not done
with water.
Clothes in the dry cleaning machine are soaked and agitated in the solvent during the wash cycle. After the wash cycle is complete, the machine spins the clothes in a spin cycle to remove the solvent. The final cycle is the drying cycle, where hot air is added and the volatile solvent vaporizes and is removed with the air stream. A dry cleaning machine is located below.
Why "dry" cleaning?
Surprisingly enough, water can be a harsh solvent. Water has a very polar molecular structure and has the ability to absorb into certain fibers causing the actual fiber to swell. This swelling action can damage or even ruin the fabrics. This is why certain clothing must be dry cleaned and is not suitable for traditional washing methods.
"Green" Dry Cleaning
Despite the dry cleaning industry's move to more environmentally friendly solvents in the mid-90s, perchloroethlyene (perc) is still widely used. The abundant use of perc results in both environmental and personal exposures which have serious negative health and ecological effects. Because of this, there is considerable pressure for the dry cleaning industry to operate in a cleaner manner. This shift to more conservative, environmentally friendly operation is commonly referred to as "Green" Dry Cleaning. Dry cleaners can be come "green" by using newer dry cleaning machines that reclaim and recycle greater amounts of solvent than old machines, implementing practices that minimize solvent exposure to employees and solvent loss to the environment, and by finding environmentally friendly substitute solvents. Perhaps the most radical move to "green" operation has come about in the use of liquid carbon dioxide (CO2) as a dry cleaning solvent. The substitution of a hazardous solvent by a benign, environmentally friendly solvent is an example of a real world case where "green" chemistry is being practiced and sought after.
History of dry cleaning
Dry cleaning is not a new concept; it has been around since the mid 1800s. Through
a fortuitous accident, a French dye-works owner named Jean Baptiste Folly
discovered that his tablecloth became cleaner after kerosene was spilled on
it from an overturned lamp. From that point on, Jean Baptiste Folly began
offering a new laundering service through his dye-works company known as
"dry cleaning."
Many different solvents have historically been used in dry cleaning processes.
In the earliest days even gasoline and kerosene were used to clean fabrics.
Until the mid 1990s carbon tetrachloride and trichloroethylene were the
common dry cleaning solvents used in the U.S. EPA regulations banned the use
of these solvents due to their hazardous nature in 1994. Conventional dry cleaners
today use one of two different solvents: perchloroethylene (perc) or petroleum
based solvents.
How dry cleaning works
Dry cleaning machines are not that different from the washer and dryer that you have at home. More recent dry cleaning machines run the wash and drying cycles through one machine in order to minimize solvent loss to the environment. The act of transferring clothes from the washer to the dryer results in significant environmental and worker contamination by the solvent and considerable monetary losses by the dry cleaner in solvent costs. Although separate units (transfer machines) are still used today, the two-in-one unit is becoming more popular and common.
This research project focuses on the benefits of "green" dry cleaning. Once the dry cleaning
process is understood, and the industry trends (total production and geographical prevalence)
have been investigated, it will be possible to investigate the possible impact that "green" dry
cleaning operations might have if they are implemented.
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