How Dry Cleaning Works

By: Debra Luhring, Nate Marks & Patrick J. Kiger  | 

dry cleaning
Freshly cleaned and pressed shirts are the hallmarks of the dry cleaning industry, but do you know how the process works? Justin Sullivan/Getty Images

Doing laundry has been a common household activity for years. Whether the techn­ology­ was­ beating the garments on rocks by the river or pushing buttons on programmed washing machines, this process depends on water and a mechanical action usually assisted by soap or an alkali. The purpose of an alkali is to saponify the oils and dislodge ordinary soil and other matter. More often than not, the soapy agent holds soil in suspension as it becomes loose during the wash cycle, and is subsequently flushed away during the rinse cycle and centrifugal spin.

The drying process for doing laundry at home is either hanging clothes on a clothesline or tumbling them in a gas- or electric-heated dryer.

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Dry cleaning, on the other hand, is different. It's a process that cleans clothes without water. The cleaning fluid that is used is a liquid, and all garments are immersed and cleaned in a liquid solvent — the fact that there is no water is why the process is called "dry." In this article, we will take a behind-the-scenes look at the dry-cleaning process so that you can understand what happens to your clothes after you drop them off at the cleaners!

Dry Cleaning Evolution

Efforts to clean clothing without soap and water go back a long time. One early pioneer was Thomas Jennings, a black freedman who was a tailor in New York City. He wasn't satisfied with laundry methods of the day, and in 1821 was granted a patent for a process called dry scouring, which was advertised as being able to remove dirt and grease from clothing while allowing garments to retain their original shape. The details of his method, sadly, are lost to history, due to an 1836 fire that destroyed the paperwork for scores of patents. Jennings apparently used his earnings from his invention to support the abolitionist movement, and helped to organize the Legal Rights Association, a group that raised court challenges to discrimination [sources: Matchar, NIHF].

In 1855, Jean Baptiste Jolly, a French dye-works owner, noticed that his tablecloth became cleaner after his maid accidentally overturned a kerosene lamp on it. Operating through his dye-works company, Jolly offered a new service and called it "dry cleaning."

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Early dry cleaners used a variety of solvents including kerosene — to clean clothes and fabrics. In the United States, the dry-cleaning industry is fairly new and has developed only during the past 75 years. After World War II, the volatile synthetic solvents carbon tetrachloride and trichlorethylene gave way to a product known as perchlorethylene (perc), which became the prevalent solvent choice for the industry. It was safer to handle, but did a much better job of cleaning, required less massive equipment and floor space, and could be utilized in retail locations offering one-hour service.

Perc is still widely used in the dry cleaning industry, but there's been increasing attention to its potential health risks. Short-term inhalation exposure can result in upper-respiratory tract and eye irritation, kidney dysfunction and neurological effects, among other health concerns, and exposure to perc been associated with several types of cancers in workers [source: EPA, Erickson]. EPA required dry cleaning facilities located in residential buildings had to stop using the chemical in December 2020 [source: Burke]. California's ban on perc goes into effect in 2023 and several other states are studying bans on the chemical as well [source: EPA].

In New York state, managers of dry cleaning businesses are required to receive special safety training, machines that use perc must be certified, and the businesses must document the use of perc and other hazardous substances [source: NYC Business]. In California, concerns about perc contaminating the air led the state to phase out its use by 2023 [source: California Air Resources Board]. In a March 2021 article in the journal Frontiers in Public Health, several public health and environmental experts called for the industry to move to different solvents, while cautioning that more evaluation of those alternatives is needed to determine their long-term health effects as well [source: Ceballos].

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The Process

dry cleaning
Do your clothes actually stay dry after you hand them over to the dry cleaner? Justin Sullivan/Getty Images

When you drop your clothes off at the cleaners, the employees follow a pattern that holds true at just about any dry-cleaning operation running today. Your clothes go through the following steps:

  1. Tagging and inspection - Some method, whether it is small paper tags or little labels written on a shirt collar, is used to identify your clothes so they don't get mixed up with everyone else's. Clothes are also examined for missing buttons, tears, etc. that the dry cleaner might get blamed for otherwise.
  2. Pre-treatment - The cleaner looks for stains on your clothes and treats them to make removal easier and more complete.
  3. Dry cleaning - The clothes are put in a machine and cleaned with a solvent.
  4. Post-spotting - Any lingering stains are removed.
  5. Finishing - This includes pressing, folding, packaging and other finishing touches.

The following sections look at each of these steps in detail.

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Tagging

dry cleaning
Numbered dry cleaning tickets keep clothes and their owners matched up from beginning to end. Portland Press/Getty Images

When you drop off your clothes, every order is identified. Although the exact identification process may vary from dry cleaner to dry cleaner, it basically includes counting the items and describing them (e.g., shirt, blouse, slacks). Also noted is the date they were dropped off and what date they'll be ready for the customer to pick up. Then, a small, colored tag is affixed to each piece of clothing with a safety pin or staple, and this tag remains attached to the clothing during the entire dry-cleaning cycle. The dry cleaner also generates an invoice, and information about the order — including the customer's name, address and phone number — is entered into a computer. This helps to keep track of the order.

If a garment needs special attention, such as removing a red wine stain from a shirt or putting a double-crease in pant legs, there's a special colored tag that gets affixed to that particular item of clothing. Once the clothing has been washed or dry cleaned, it goes through a quality check and the order gets re-assembled. This means the clothing is bundled together for the customer to pick up. Remember, every order is identified by a colored tag with a number on it so the person who re-assembles the order knows which shirts and which slacks go together and to whom they belong.

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Should You Pre-treat Stains?

Though recommendations vary, some dry cleaning websites advise that it's not necessary to treat stains prior to taking garments to the dry cleaner, and some dry cleaner websites caution against it, because there's a risk that you may actually make stains hard for the dry cleaner to remove. Cleaners have a variety of fluids that they can use to remove stains from fabric, which act in a different way than the water that you might use. However, it's important to alert your cleaner to everything that you've spilled on the clothing, because the residue from those substances can cause trouble during dry cleaning and worsen the damage to your clothing [source: Captain Dry Clean].

If you don't know what to do when a stain happens, call your cleaner and ask him or her what to apply.

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Dry Cleaning

Despite the name, the clothes don't stay dry during dry cleaning. They actually get wet! While there are many brands and makes of cleaning machines, they are all basically the same in principle and function. A cleaning machine is a motor-driven washer/extractor/dryer that holds from 20 to 100 pounds (9 to 45 kg) of clothes or fabrics in a rotating, perforated stainless-steel basket. The basket is mounted in a housing that includes motors, pumps, filters, still, recovery coils, storage tanks, fans and a control panel. In all modern equipment, the washer and the dryer are in the same machine. Doing this makes it possible to recover nearly all of the perc used during cleaning, which is better for the environment and saves the dry cleaner money.

As the clothes rotate in the perforated basket, there is a constant flow of clean solvent from the pump and filter system. The solvent sprays into the basket and chamber constantly — not only immersing the clothes, but gently dropping and pounding them against baffles in the cylinder as well. The dirty solvent is pumped continuously through the filter and re-circulated free and clear of dirt that gets trapped in the filter.

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As an example, a typical machine might pump solvent through the clothes at a rate of perhaps 1,500 gallons (5,678 liters) per hour. The most commonly used solvent is perchloroethylene, known in the industry as "perc." Perc is about 69 percent heavier than water. If a cycle lasts for eight minutes, the clothes would be doused during mechanical action with 200 gallons (757 liters) of solvent. This is more than adequate to thoroughly clean the clothes.

The next cycle drains and rapidly spins the clothes to expel the solvent and then goes into a dry cycle by circulating warm air through the clothes. The remaining fumes and solvent are vaporized by warm air, condensed over cooling coils, and then passed through a secondary air control to get the solvent out

The distilled solvent is separated from any water (that may have remained in the clothes or system) and returned to the tank as distilled solvent. Since any moisture that may have condensed into water during the process floats on top of perc, it is relatively simple to separate it.

Regardless of which solvent the dry cleaner uses, the quality of cleaning, the degree of soil removal, the color brightness, the freshness, the odor and the softness all depend on the degree to which the cleaner controls his filter and solvent condition and moisture. Quality control can vary day to day unless the cleaner is constantly attentive to these factors.

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Post-spotting

Post-cleaning spot removal is another part of the quality control process. Post-spotting, as it is called, uses professional equipment and chemical preparations using steam, water, air, and vacuum. Post-spotting involves a fairly simple process for removing a stain. If the stain had water in it to begin with (bean soup, for example), then it takes water or wet-side chemicals to remove the stain. If the stain was on the dry side (grease, oil-based paint, tar, nail polish), it takes solvents or dry-side chemicals to remove the stain.

In home laundry, most wet-type stains come out during the washing process. Grease does not. The opposite is true in dry cleaning — it will leave the wet-side stains intact after the cleaning cycle. On the other hand, the solvent removes grease and oils during the cleaning cycle. The exception to this rule involves incorporating a "charge" of specially formulated dry-cleaning soap (an anhydrous emulsifier) into the cleaning cycle.

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The dry cleaner will examine your clothes after cleaning is complete to see if any stains remain. If they do, post-spotting tries to get them out. A conscientious cleaner will remove the overwhelming majority of soil and stains, but there is always a small percent of very stubborn stains that may not be entirely removed for a variety of reasons, such as:

  • Tannin stains set by heat and time
  • Original dye stripped or faded
  • Bleached-out spots or sun-faded materials
  • Foreign dye deposit

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Finishing

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A worker uses a pressing machine to press shirts in the finishing stages of the dry cleaning process. Justin Sullivan/Getty Images

The final phase of dry-cleaning operations includes finishing, pressing, steaming, ironing, and making any necessary repairs to restore the garment. This is the least mysterious process since most dry-cleaning stores have their professional finishing equipment in plain view of customers.

Once the clothes are cleaned, they are pressed or "finished." The steps in this process include:

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  • Applying steam to soften the garment
  • Re-shaping it through quick drying
  • Removing the steam with air or vacuum
  • Applying pressure to the garment

The pressure comes from the head of the pressing machine, while steam is diffused through the bottom. Most machines not only emit steam, but can vacuum it out as well!

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Industry Trends

The demand for environmentally safe products has increased in recent years as a result of government regulations and greater consumer awareness of environmental issues.

As a replacement for perc, alternative solvents have been developed, including ones that utilize silicone and chemicals from corn, as well as hydrocarbon-based solvents [sources: NY.gov, Coons, Leverette].

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The EPA and organizations such as the Toxics Use Reduction Institute at the University of Massachusetts Lowell have encouraged dry cleaners to move to a process called professional wet cleaning, which uses water and biodegradable detergents in computer-controlled machines. Garments are then finished with tensioning and pressing equipment [sources: Onasch,Turi.org, EPA]. According to the institute, some cleaners who've switched to wet cleaning have reported savings in energy costs and water use as well [source: Turi.org] In Washington state, King County, where Seattle is located, has offered grants to dry cleaners to cover a portion of the estimated $40,000 to $60,000 cost of switching to wet cleaning [source: O'Neill].

While some in the industry have been skeptical about whether wet cleaning works as well as conventional dry cleaning, proponents say that advances in wet cleaning systems can handle most fabrics [source: Hay].

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Originally Published: Apr 1, 2000

Dry Cleaning FAQs

Is it possible to dry clean at home?
Yes. Using a mild detergent, machine wash cold on a gentle cycle. Be sure to take out clothes as soon as the cycle stops, and dry them by laying them down on a flat surface. Should you wish to do so manually, fill a tub with cold water and add to it some Woolite, or a similar detergent.
What's better, dry cleaning or washing?
When it comes to tackling stubborn stains such as those left by grease and oil, a simple wash might not be able to do a good job of cleaning these, so dry cleaning is preferred.
What chemicals are used in dry cleaning?
Garments are immersed in liquid solvent that contains little to no water, along with "perc" or tetrachloroethylene (perchloroethylene).
Why should I opt for dry cleaning?
Delicate and tricky fabrics like cashmere and wool can be ruined by regular washing machines. Dry cleaning prioritizes fabric care and keeps clothes from shrinking or being stretched out.

Lots More Information

Related Articles

More Great Links

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