So, do cleaners spray a powder on clothes or something? In medieval times a clay called "Fullers earth" was used to absorb oils and soils from wool, but dry cleaning today involves washing garments in a liquid, usually a chemical solvent. Modern dry cleaning dates back to an accidental discovery that when a whale oil lamp was tipped over, a tablecloth got cleaner, not dirtier. It turns out that clothes can be "washed" in liquids other than water. In the US the name for washing a garment in a liquid that isn't water is "Dry Cleaning", but it's "dry" only in the sense that the liquid isn't water. If you watched the garments, you'd see them sloshing around in a sudsy liquid, and then being dried.
Many different liquids have been used over the years. In the 20's and 30's, a petroleum solvent, similar to gasoline was used, but it was highly flammable, and smelly. In those days dry cleaners often burned down, so in the 50's most cleaners switched to a non-flammable solvent, percholorethylene, also called tetracholoroethylene. It is considered a probable human carcinogen today, and is a noted ground water contaminant. About half of all cleaners still use it, but a few have moved to other chemicals.
Some cleaners have gone back to petroleum solvents (also called "hydrocarbon"), not to the old, explosive, smelly petroleum solvents of the 20's, but to new petroleum solvents that are odorless, and have a higher flash point. Others have gone to a synthetic silicone based solvent, decamethylcyclopentasiloxane (also called "Green Earth"). At Hangers, for the last 15 years we have cleaned with liquid CO2. CO2 is a liquified gas, part of the air we breathe. It's odor free, and can't be left behind. We love working with it, and we love how the clothes come out.
One of the biggest differences between the various solvents are the boiling points and the evaporation rates. Most people are familiar with water, which boils at 212 degrees, and how it is dried. It is dried out of clothes by blowing hot air over clothes while they tumble. In addition to removing the water, the heat makes the fibers brittle, the tumbling breaks some of them off, and the movement of the air carries those fibers to the lint filter, where it accumulates. Lint is simply the broken off fibers. The more lint that is removed in each cleaning, the shorter the life of a garment.
The old traditional dry cleaning solvent, perchloroethylene, boils at about 262 degrees, but it dries fairly quickly. That means that less heat is needed with perc than with water, and it can be dried at relatively low temperature. As a result you get less lint than you do with laundry, meaning that dry cleaning will extend the life of your garments. Liquified CO2 has a very low boiling point, and evaporates almost instantly, but if you let it evaporate that fast, it will freeze into dry ice. Instead of blowing hot air over it, we gradually remove the CO2 with a special air compressor, which compresses it back into liquid form. As CO2 is removed, the clothes get colder, but not cold enough to freeze. With the garments kept cold, and with a dry cycle only about 15 minutes long, you get almost no lint, which means much longer garment life.
The other solvents in use today, decamethylyclopentasiloxane ("Green Earth") and petroleum ("Hydrocarbon"), have higher boiling points (over 400 degrees), and dry very slowly. They require much more heat, higher temperatures, and extended drying times compared to perc or CO2. Back in 2000 a leading consumer magazine compared cleaning in liquid CO2 to cleaning with high temperature solvents, and the the garments cleaned in liquid CO2 came out much better, looking more like new.
What are the environmental effects of the various solvents? CO2 has no negative effects in the form of air or water pollution, and can not be left in the garment. Some are confused that it may increase environmental CO2 levels, but you have to separate things that operate as a closed loop, from ones that remove carbon from long term storage. As an example, fermenting grass releases CO2, but when the grass regrows, it reabsorbs the CO2. Our CO2 is a byproduct of ethanol manufacturing, and if we didn't use it, it would end up directly in the atmosphere, and it is removed again when the next corn is grown.
Solvents derived from petroleum ("hydrocarbon" and "perc") do lead to a net increase in CO2 in the atmosphere. Both are also potential ground water contaminants, particularly "perc", which has led to many expensive cleanups nationwide. Decamethylcyclopentasiloxane ("Green Earth") breaks down into silica, and is not a ground water contaminant, but there are some studies that have found some persistence in human and animal tissue.
For more information, here's a link to a SF Environmental article about the various dry cleaning solvents in use today.
Before we became Hangers Cleaners and made the switch to liquid CO2, we cleaned clothes in perchloroethylene and in hydrocarbon, and we tried a few other solvents that were in use at the time. After we had been cleaning in CO2 for a couple months, I asked my long term employees "If you had a choice, and could clean your personal clothes by any of the methods we have ever used, which would you choose?" There was silence as they all stared at me as if I was totally insane. Finally they said "Are you nuts? CO2, of course. Nothing else comes close." I still feel that way. I love how my own clothes come out when cleaned in CO2, and they seem to last forever now.
Give Hangers a try, and you'll be surprised at how nice and fresh your garments come back, and especially at how long they last.
#drycleaning, #solvents, #longergarmentlife, #CO2drycleaning