We Used To Clean Our Clothes With Gasoline

Dry cleaning isn’t dry.

You thought it was, didn’t you?

It’s not.

They call it dry cleaning because it doesn't wet your clothes with water the way your washing machine does.

But it still uses wet chemicals to clean fabrics.

Those chemicals can be pretty toxic.

Which is nothing new.

For as long as dry cleaning has been a thing, we’ve known it’s pretty bad for us.

So you’d think maybe we would have done something about that by now.

The good news is: we have!

The bad news is: every time we come up with a promising new chemical, we discover some new problem with it.

But researchers are finally getting close to identifying that elusive substance that can remove grease stains, not poison the neighborhood, and clean up dry cleaning’s reputation.

Most of your clothes can be washed in a regular washing machine with good old soap and water.

But if you have anything made of wool, silk, or suede, check the tag first.

It might be dry clean only.

And if you’ve ever, like, rolled the dice and thrown your dry-clean-only clothes in the washing machine, you know how shrunken, discolored, and shapeless they can turn out.

Dry cleaning takes it a little easier on those special materials that can’t handle the washing machine.

The spin cycle doesn’t whip your clothes around quite as hard.

Aside from being gentler, one of the big differences between dry cleaning and your laundromat is the cleaning solution.

The liquid that dry cleaners use has changed a lot over the last couple of centuries.

Back in the 1800s, before washing machines were invented, the first American dry cleaners would hand-wash garments in tubs of gasoline or kerosene.

Believe it or not, that got the stains out.

And their wool clothes didn’t shrink.

It worked through the power of polarity …or lack of polarity.

The water we use for regular washing is polar.

The two hydrogen atoms have slight positive charges, and the oxygen atom carries a slight negative charge.

This makes opposite charges on opposite sides of the whole water molecule.

And water isn’t the only polar molecule out there.

The salt in your sweat is also polar.

Which we can use to our advantage because polar molecules dissolve other polar molecules.

So washing your clothes in water gets rid of the salty sweat on them.

But not all molecules are arranged with their charges on opposite sides like that.

Greases and oils are nonpolar.

While individual atoms within each molecule might carry a slight charge, the molecule as a whole doesn’t have entire areas that trend positive or negative.

And we can use that to our advantage, too.

Like, polar water dissolves polar salt, nonpolar gasoline dissolves nonpolar oils.

That’s why certain tough oil stains need dry cleaning.

This concept of polarity is also why certain materials need to be dry cleaned.

Because salt isn’t the only polar thing for water to attack in your washing machine.

Natural fibers can also have polar molecules in them, which expand when they absorb water, catch onto each other in the tumble, and tighten the weave, ultimately shrinking your wool clothes in a regular washing machine.

Most dry cleaning solvents, including older ones like kerosene, are nonpolar.

So they can draw out stubborn grime that water just can’t wash out, and they don’t affect natural fibers in the same way.

But cleaning clothes in gasoline also meant that clothes came out smelling like gasoline.

And there were also, like, open tubs of gasoline, like, just sitting around in these places!

So it probably won’t surprise you that these dry cleaning operations had a tendency to sometimes explode.

To deal with some of the flammability issues, many dry cleaners switched to Stoddard solvent in the early 20th century.

Stoddard solvent is a mixture of carbon-based liquids that formed when refining crude oil.

Today, you might know this as paint thinner.

It’s also nonpolar and works in a similar way to gasoline to cut through oil stains in your clothes.

And yeah, Stoddard solvent is less flammable than gasoline.

It still burns pretty easily, though.

And breathing its vapors can irritate your eyes and skin, and make you dizzy, and give you headaches.

So dry cleaning started out with kerosene and paint thinner… which sound like stuff you’d want to wash out of your clothes instead of washing your clothes with.

But it turns out, they worked pretty well for dissolving grease and grime that water just can’t tackle.

And luckily, there were ways to get that same cleaning power without risking a fire.

In the first half of the 20th century, dry cleaners started introducing nonflammable chlorinated solvents.

These are chemicals that have chlorine atoms attached to a carbon backbone.

Popular options included carbon tetrachloride, trichloroethylene, and perchloroethylene, otherwise known as perc.

And some people really seem to like perc.

Since the 1940s, perc has been the most commonly used dry cleaning fluid in the US and Europe.

Just like gasoline and Stoddard solvent, perc is nonpolar.

It soaks into your clothes and dissolves nonpolar grime without affecting the polar molecules in the fibers.

But it is not perfect.

Perc doesn’t handle polar dirt very well, so you might have to spot-clean that stuff with specialized detergents.

All in all, though, that was, like, a pretty manageable downside.

For several decades, it seemed like everything was fine.

Perc got most of the stains out of dry clean only clothes, and it didn’t catch fire.

But research began to show that perc had its problems, too.

In 1991, the California Air Resources Board identified perc as a toxic air contaminant, prompting a more in-depth look at its impacts on human health and the environment.

Researchers found that breathing in the fumes can cause kidney damage, dizziness, and eye irritation in the short term.

And long-term exposure can damage your liver and probably cause cancer.

So modern dry cleaning machines are designed to minimize the amount of perc that employees come in contact with.

But even little things, like a tiny leak in the system or taking clean clothes out of the machine, can compound their exposure.

See, one of the things that makes perc a good solvent for dry cleaning is that it evaporates really easily.

That makes it easier to dry your clothes and get them back to you on time.

But it also means that people who live or work around dry cleaning facilities end up breathing in a lot of perc.

Individual dry cleaning operations don’t usually release a lot of perc at once.

But the continuous exposure from cleaning the machines and moving clothes around means that even people near dry cleaning facilities can end up breathing in a lot of perc over time.

Based on this research, the US Environmental Protection Agency banned the use of perc in any dry cleaning business located inside a residential building.

And some states are phasing out perc entirely.

California banned perc in all dry cleaning operations in 2023, and Minnesota’s ban will take effect in 2026.

But we are still making fancy suits and wool socks, which means the need for dry cleaning isn’t gonna go away anytime soon.

Ideally, we would replace perc with something less hazardous, and there are a few options in the works.

Before I tell you more about that, though, first, an ad.

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Among the most popular new dry cleaning chemicals are high-flashpoint hydrocarbons.

These can be several nonpolar solvents, each containing somewhere between 11 and 15 carbon atoms in a long chain.

Hydrocarbons are a popular alternative to perc because we already know they work well.

Basically, we’re going back to the same class of chemicals as kerosene and gasoline.

Which still leaves us with the flammability issue.

But the newer hydrocarbon mixtures are designed to be less flammable than gasoline and kerosene.

There, like, are a lot of different hydrocarbons in gasoline, but most of them contain six or fewer carbon atoms.

Longer hydrocarbons, like high-flashpoint hydrocarbons, have a large size that allows molecules to interact with each other more and that keeps them liquid and makes it harder for them to evaporate.

Less evaporation means less flammable vapors.

But they are still more flammable than perc.

Another option is butylal.

Butylal is mostly made of hydrocarbons, and it cleans your clothes in the same way, but it has a few oxygen atoms stuck in the middle of the chain.

Those extra oxygen atoms make it somewhat biodegradable.

In the presence of water and acid, butylal breaks down into butanol and formaldehyde.

And those chemicals don’t stick around as long as perc.

Butylal also doesn’t evaporate easily.

Dry cleaners can still dry it out of your clothes, but it poses less of an inhalation risk to people nearby.

A 13 week study showed that rats who breathed in butylal didn’t have any long-term negative effects.

We’re still waiting on the human version of that study, though.

Until then, for those concerned about flammability, there is liquid carbon dioxide.

Carbon dioxide is nonpolar, and it dissolves nonpolar contaminants the same way as perc and hydrocarbons.

Some studies have shown that liquid CO2 works about as well as perc at removing nonpolar grime.

But, as you might expect, liquid CO2 doesn’t dissolve polar compounds very well.

Carbon dioxide still has a lot going for it, though.

It’s nonflammable and nontoxic, but the process of washing your clothes with a liquefied gas is a bit more complicated than a regular rinse.

First, the washing machine pulls all the air out of the drum.

Then it adds in both liquid and gaseous carbon dioxide.

To keep most of the CO2 in a liquid state, and avoid making a giant bomb, your clothes get washed under high pressure and at low temperature.

When it’s time to take the clothes out, a gas compressor pulls the carbon dioxide out of the drum and back into a storage tank, so it doesn’t get vented to the atmosphere.

Because carbon dioxide is a gas at room temperature and pressure, it evaporates during this decompression step.

No heat or dryer needed!

The problem is, because of that process, it doesn’t remove stuff like dirt and sand as well as other solvents.

Normally, the force of a garment splashing around in a liquid knocks the dirt loose.

That force partly depends on the density of the solvent.

But liquid CO2 has a very low density, so it’s not as effective at shaking out small particles.

Since none of those alternatives are perfect, perhaps the safest and most environmentally-friendly option is professional wet cleaning.

Yes, we are back to using good old fashioned nonflammable, nontoxic water instead of carbon-based solvents.

Professional wet cleaning is a lot like using a regular washing machine.

Except the washing machine is super high-tech.

It’s gentle on clothes and designed to mimic the mechanical actions of hand-washing.

Professional wet cleaners use a computer to control the drum’s rotations, so the process is safe for those delicate clothes that just can’t tolerate being beaten up in the regular wash.

The computer also lets you dictate exactly how much and what type of detergents to use.

Some manufacturers have developed special detergents specifically for professional wet cleaning.

Often, these include compounds called ethoxylated alcohols.

In those compounds, one end of the chemical mixes well with oils and the other end mixes with water.

This helps the detergent pull greasy stains out of your clothes and into the water that gets washed away at the end of the cycle.

With futuristic machines and carefully curated detergents, most garments that would normally be dry cleaned in perc can be professionally wet cleaned.

But wet cleaning still isn’t a perfect solution.

Because water is polar, it doesn’t handle some oil-based stains well.

Some dry cleaners who made the switch to wet cleaning reported trouble getting those greasy stains out.

As the dry cleaning industry moves to adopt safer solvents, scientists and public health officials are keeping an eye on how those solvents affect you.

Just like in the past, it’s always possible that somewhere down the line, one or more of these new options will pose a hazard we don’t know about yet.

But we have come a long way from scrubbing our shirts in gasoline!

And just like we have for the last 200 years, we’re gonna keep coming up with something better.

Who knows?

Maybe the downsides of future dry cleaning advances will be small enough that they’ll come out in the was