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How Does Dry Cleaning Work?

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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.

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Big Questions
Why Don't We Eat Turkey Tails?
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Turkey sandwiches. Turkey soup. Roasted turkey. This year, Americans will consume roughly 245 million birds, with 46 million being prepared and presented on Thanksgiving. What we don’t eat will be repurposed into leftovers.

But there’s one part of the turkey that virtually no family will have on their table: the tail.

Despite our country’s obsession with fattening, dissecting, and searing turkeys, we almost inevitably pass up the fat-infused rear portion. According to Michael Carolan, professor of sociology and associate dean for research at the College for Liberal Arts at Colorado State University, that may have something to do with how Americans have traditionally perceived turkeys. Consumption was rare prior to World War II. When the birds were readily available, there was no demand for the tail because it had never been offered in the first place.

"Tails did and do not fit into what has become our culinary fascination with white meat," Carolan tells Mental Floss. "But also from a marketing [and] processor standpoint, if the consumer was just going to throw the tail away, or will not miss it if it was omitted, [suppliers] saw an opportunity to make additional money."

Indeed, the fact that Americans didn't have a taste for tail didn't prevent the poultry industry from moving on. Tails were being routed to Pacific Island consumers in the 1950s. Rich in protein and fat—a turkey tail is really a gland that produces oil used for grooming—suppliers were able to make use of the unwanted portion. And once consumers were exposed to it, they couldn't get enough.

“By 2007,” according to Carolan, “the average Samoan was consuming more than 44 pounds of turkey tails every year.” Perhaps not coincidentally, Samoans also have alarmingly high obesity rates of 75 percent. In an effort to stave off contributing factors, importing tails to the Islands was banned from 2007 until 2013, when it was argued that doing so violated World Trade Organization rules.

With tradition going hand-in-hand with commerce, poultry suppliers don’t really have a reason to try and change domestic consumer appetites for the tails. In preparing his research into the missing treat, Carolan says he had to search high and low before finally finding a source of tails at a Whole Foods that was about to discard them. "[You] can't expect the food to be accepted if people can't even find the piece!"

Unless the meat industry mounts a major campaign to shift American tastes, Thanksgiving will once again be filled with turkeys missing one of their juicier body parts.

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

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Big Questions
Why Do We Dive With Sharks But Not Crocodiles?
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Why do we dive with sharks but not crocodiles?

Eli Rosenberg:

The issue is the assumption that sharks' instincts are stronger and more basic.

There are a couple of reasons swimming with sharks is safer:

1. Most sharks do not like the way people taste. They expect their prey to taste a certain way, like fish/seal, and we do not taste like that. Sharks also do not like the sensation of eating people. Bigger sharks like great whites enjoy prey with a high fat-bone ratio like seals. Smaller sharks enjoy eating fish, which they can gobble in one bite. So, while they might bite us, they pretty quickly decide “That’s not for me” and swim away. There is only one shark that doesn’t really care about humans tasting icky: that shark is our good friend the tiger shark. He is one of the most dangerous species because of his nondiscriminatory taste (he’s called the garbage can of the sea)!

2. Sharks are not animals that enjoy a fight. Our big friend the great white enjoys ambushing seals. This sneak attack is why it sometimes mistakes people for seals or sea turtles. Sharks do not need to fight for food. The vast majority of sharks species are not territorial (some are, like the blacktip and bull). The ones that are territorial tend to be the more aggressive species that are more dangerous to dive with.

3. Sharks attacked about 81 people in 2016, according to the University of Florida. Only four were fatal. Most were surfers.

4. Meanwhile, this is the saltwater crocodile. The saltwater crocodile is not a big, fishy friend, like the shark. He is an opportunistic, aggressive, giant beast.


5. Crocodiles attack hundreds to thousands of people every single year. Depending on the species, one-third to one-half are fatal. You have a better chance of survival if you played Russian roulette.

6. The Death Roll. When a crocodile wants to kill something big, the crocodile grabs it and rolls. This drowns and disorients the victim (you). Here is a PG video of the death roll. (There is also a video on YouTube in which a man stuck his arm into an alligator’s mouth and he death rolled. You don’t want to see what happened.)

7. Remember how the shark doesn’t want to eat you or fight you? This primordial beast will eat you and enjoy it. There is a crocodile dubbed Gustave, who has allegedly killed around 300 people. (I personally believe 300 is a hyped number and the true number might be around 100, but yikes, that’s a lot). Gustave has reportedly killed people for funsies. He’s killed them and gone back to his business. So maybe they won’t even eat you.


8. Sharks are mostly predictable. Crocodiles are completely unpredictable.

9. Are you in the water or by the edge of the water? You are fair game to a crocodile.

10. Crocodiles have been known to hang out together. The friend group that murders together eats together. Basks of crocodiles have even murdered hippopotamuses, the murder river horse. Do you think you don't look like an appetizer?

11. Wow, look at this. This blacktip swims among the beautiful coral, surrounded by crystal clear waters and staggering biodiversity. I want to swim there!

Oh wow, such mud. I can’t say I feel the urge to take a dip. (Thanks to all who pointed this out!)

12. This is not swimming with the crocodiles. More like a 3D aquarium.

This post originally appeared on Quora. Click here to view.

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