How Does Dry Cleaning Work?


The term “dry cleaner” first appeared on a list of occupations inscribed on a Mycenaean clay tablet dating from 1600-1100 BCE. Van Sigworth of the National Institute of Drycleaning posits that this likely referred to the use of grease-absorbing dirt and sand to remove stubborn stains. This was truly “dry” cleaning—a claim that can't be made about our contemporary versions.

The specifics of the story vary, but the first modern dry cleaner is often said to be a Frenchman named Jean-Baptiste Jolly or Jolly Belin (depending on whom you ask). In the early 19th century, Jolly accidentally spilled kerosene (or was it turpentine?) from a lamp onto a greasy tablecloth. When the spot dried, he noticed it was remarkably clean. After a little experimenting, the enterprising Jolly found that the petroleum-based fluid worked to wash all sorts of delicate fibers.

The first commercial dry cleaners opened in Paris in 1825 (or ’45) under the name "Jolly Belin." For the next one hundred years or so, dry cleaning companies relied on kerosene, or the equally combustible benzene and gasoline, to banish stains. The fire threat these solvents posed made it difficult for dry cleaners to obtain insurance—not to mention risky for them to operate. In the 1930s, people began experimenting with different solvents less likely to set their businesses aflame, and in 1948 the industry settled on a non-flammable halogen compound called perchloroethylene, or "perc," for short.

Wash, Rinse, Repeat

For the most part, perc is what dry cleaners still use today. After clothes are loaded into what resembles a normal washing machine, the rotating drum fills with the chemical. The machine is then agitated to scrub stains away; post-cycle, the perc drains out of the drum to be stored for another load. (Dirt is filtered out of the solvent before it drains or it is distilled later so the liquid can be used again.) At some point in the process, specific water-soluble stains are treated. Finally, clothes are pressed and returned in one of those annoyingly clingy plastic bags.

For a quick overview of this process, check out the video below:

The Problem with Perc

Perc reigned supreme as the dry cleaning chemical of choice until the mid-1990s, when a series of scientific studies delivered a hit to its reputation. (One scary Seattle-based study found that rates of esophageal and bladder cancers among dry cleaning workers increased by a factor of about two.) Today, the EPA concedes that Tetrachloroethylene (another name for perc) is “likely to be carcinogenic to humans” and “may also cause adverse effects in the kidney, liver, immune system and hematologic system, and on development and reproduction.”

Today, those searching for perc-free alternatives generally have one of three options, thanks to so-called “Organic” or “Green” cleaners. Option one is siloxane, a silicone-based chemical solvent that is biodegradable and is not believed to be a health risk. Good old-fashioned (and cheap!) hydrocarbon can be used, too, and though it’s generally thought to be safer than perc, it can leave a chemical odor on clothes. The newest (and priciest) innovation in dry cleaning uses CO2 as a solvent—although most neighborhood shops can’t yet afford the machines that convert carbon dioxide from its gas form to a liquid.

The simplest non-perc solution for businesses looking to attract conscious consumers is “wet cleaning,” in which—you guessed it—regular old water is heated to a desired temperature then used to scrub out stains.

AFP, Getty Images
Big Questions
What Happened to the Physical Copy of the 'I Have a Dream' Speech?
AFP, Getty Images
AFP, Getty Images

On August 28, 1963, Martin Luther King Jr. stood on the steps of the Lincoln Memorial and gave a speech for the ages, delivering the oratorical masterpiece "I Have a Dream" to nearly 250,000 people.

When he was done, King stepped away from the podium, folded his speech, and found himself standing in front of George Raveling, a former Villanova basketball player who, along with his friend Warren Wilson, had been asked to provide extra security around Dr. King while he was speaking. "We were both tall, gangly guys," Raveling told TIME in 2003. "We didn't know what we were doing but we certainly made for a good appearance."

Moved by the speech, Raveling saw the folded papers in King’s hands and asked if he could have them. King gave the young volunteer the speech without hesitation, and that was that.

“At no time do I remember thinking, ‘Wow, we got this historic document,’” Raveling told Sports Illustrated in 2015. Not realizing he was holding what would become an important piece of history in his hands, Raveling went home and stuck the three sheets of paper into a Harry Truman biography for safekeeping. They sat there for nearly two decades while Raveling developed an impressive career coaching NCAA men’s basketball.

In 1984, he had recently taken over as the head coach at the University of Iowa and was chatting with Bob Denney of the Cedar Rapids Gazette when Denney brought up the March on Washington. That's when Raveling dropped the bomb: “You know, I’ve got a copy of that speech," he said, and dug it out of the Truman book. After writing an article about Raveling's connection, the reporter had the speech professionally framed for the coach.

Though he displayed the framed speech in his house for a few years, Raveling began to realize the value of the piece and moved it to a bank vault in Los Angeles. Though he has received offers for King’s speech—one collector wanted to purchase the speech for $3 million in 2014—Raveling has turned them all down. He has been in talks with various museums and universities and hopes to put the speech on display in the future, but for now, he cherishes having it in his possession.

“That to me is something I’ll always be able to look back and say I was there,” Raveling said in the original Cedar Rapids Gazette article. “And not only out there in that arena of people, but to be within touching distance of him. That’s like when you’re 80 or 90 years old you can look back and say ‘I was in touching distance of Abraham Lincoln when he made the Gettysburg Address.’"

“I have no idea why I even asked him for the speech,” Raveling, now CEO of Coaching for Success, has said. “But I’m sure glad that I did.”

Big Questions
How Are Rooms Cleaned at an Ice Hotel?

Cleaning rooms at Sweden’s famous ICEHOTEL is arguably less involved than your typical hotel. The bed, for example, does not have traditional sheets. Instead, it’s essentially an air mattress topped with reindeer fur, which sits on top of a custom-made wooden palette that has a minimum of 60 centimeters of airspace below. On top of those reindeer hides is a sleeping bag, and inside that sleeping bag is a sleep sack. And while it’s always 20ºF inside the room, once guests wrap themselves up for the night, it can get cozy.

And, if they’re wearing too many layers, it can get quite sweaty, too.

“The sleep sack gets washed every day, I promise you that. I know it for a fact because I love to walk behind the laundry, because it’s so warm back there," James McClean, one of the few Americans—if not the only—who have worked at Sweden's ICEHOTEL, tells Mental Floss. (He worked on the construction and maintenance crew for several years.)

There isn’t much else to clean in most guest rooms. The bathrooms and showers are elsewhere in the hotel, and most guests only spend their sleeping hours in the space. But there is the occasional accident—like other hotels, some bodily fluids end up where they shouldn’t be. People puke or get too lazy to walk to the communal restrooms. Unlike other hotels, these bodily fluids, well, they freeze.

“You can only imagine the types of bodily fluids that get, I guess, excreted … or expelled … or purged onto the walls,” McClean says. “At least once a week there’s a yellow stain or a spilled glass of wine or cranberry juice … and it’s not what you want to see splattered everywhere.” Housekeeping fixes these unsightly splotches with an ice pick and shovel, re-patching it with fresh snow from outside.

Every room has a 4-inch vent drilled into the icy wall, which helps prevent CO2 from escalating to harmful levels. Maintenance checks the holes daily to ensure these vents are not plugged with snow. Their tool of choice for clearing the pathway is, according to McClean, “basically a toilet brush on a stick.”

When maintenance isn’t busy unstuffing snow from that vent hole, they’re busy piping snow through it. Every couple days, the floor of each room receives a new coat of fluffy snow, which is piped through the vent and leveled with a garden rake.

“It’s the equivalent of vacuuming the carpet,” McClean says.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at


More from mental floss studios