Ever since I was a little boy, I’ve wondered something. Somewhere in between the first time I asked myself, “Why is the sky blue?” and the first time I asked myself, “What is the meaning of life?”, I first asked myself, “What the heck is dry cleaning?”
The cleaning I knew mostly involved water–lots of it–and soap, too. Even the cleaning that didn’t involve water involved liquid. It seemed obvious to me that “dry cleaning” must somehow be done without any liquid at all. I pictured some peculiar power that was spread on clothes and then brushed off, miraculously taking all the dirt with it.
Imagine my shock when I discovered that “dry” cleaning isn’t dry at all–it uses all kinds of liquids. It’s called “dry” cleaning only because it doesn’t use water.
One reason water is so widely used for cleaning is that it’s almost a universal solvent–that is, it dissolves almost everything. Unfortunately, some of the things it doesn’t dissolve are things that are quite likely to get onto your clothes, especially greasy substances.
Clear back in the 18th century, Europeans figured out that if you want to get grease out of textiles, leathers or furs, you had to use solvents stronger than water. By the mid-19th century in France they’d discovered that kerosene and turpentine were very good solvents indeed, and commercial dry cleaning was invented.
Petroleum substances were the solvents of choice until the 1930s, when “chlorinated hydrocarbons” were developed, powerful, non-flammable solvents. One of these, “perchloroethylene,” called “perc,” for short, has been the primary solvent used by dry cleaners ever since.
The dry-cleaning process begins with clothes being tagged for owner identification; then they have to be sorted, much like you would sort clothes for the ordinary washing machine, by fiber content, color and construction: the dry-cleaning cycle has to be modified to suit various fabrics.
Stains that are likely to be difficult to remove are pre-spotted with solvent by hand. Delicate items which might not survive machine cleaning are cleaned entirely by hand; the other clothes are placed into what’s basically a glorified washing machine. Clothes are turned over and over in a special drum, through which solvent, mixed with a special detergent, flows continuously. At the conclusion of the cleaning cycle, the solvent is spun out and the clothes are dried in a tumble-type dryer or in a cabinet. Then the clothes are examined, and any remaining stains are removed by hand.
The final step is to press and steam the clothes to remove wrinkles and sharpen pleats and creases.
This process has hardly changed for decades. Although dry-cleaning fortunes took a dip in the 1960s when wash-and-wear and permanent-press fabrics were introduced, a recent return to more traditional, natural fabrics has boosted the use of dry-cleaners again.
Unfortunately, “perc,” the industry’s solvent-of-choice, has turned out to be a possible carcinogen (based on long-term animal studies using high levels of exposure). Short-term exposure to high levels of the chemical can damage the nervous system, repeated contact with it can cause skin irritation, and some studies have suggested that women who work in dry cleaning industries have more menstrual problems and spontaneous abortions than women not exposed to perc. (However, the study did not consider other possible causes, so it’s not certain perc was to blame.)
The amount of perc that remains in dry-cleaned clothes is so minimal there’s no risk to customers, but governments and environmental agencies are still anxious to find a substitute for the chemical, which finds its way into the environment and has contaminated water supplies in some areas. An estimated 225 million kilograms of the stuff is produced every year, and 40 to 45 percent of that is used by dry cleaners. Environmental regulations applied to dry cleaners have tightened considerably over the past few years to prevent spills and atmospheric emissions.
The U.S.’s Environmental Protection Agency has conducted tests on several alternate systems, including ultrasonics (using high-frequency sounds to blast dirt out), supercritical carbon-dioxide, and new petroleum-based solvents that are less environmental hazardous than perc and less flammable than their 19th-century predecessors.
The EPA even conducted a large-scale test of a system that cleaned clothes using the controlled application of heat, steam and soap. The new method worked well enough that three New York cleaning establishments now use it. The EPA has also had promising results with a new microwave drying process that seems to keep water-sensitive fabrics from shrinking.
Gee, cleaning clothes with heat, steam and soap. Could something that radical ever catch on?