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.
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 edition of HowStuffWorks, 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
Like many inventions, dry cleaning came about by accident. In 1855, Jean Baptiste Jolly, a French dye-works owner, noticed that his table cloth 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."
Early dry cleaners used a variety of solvents -- including gasoline and 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. Since World War II ended, the volatile synthetic solvents carbon tetrachloride and trichlorethylene gave way to a product known as perchlorethylene (perc), which became the overwhelming solvent choice for the industry. It was not only safer and faster, but did a much better job of cleaning, required less massive equipment, less floor space, and could be installed in retail locations offering excellent quality one-hour service.
As a result of this innovation, the majority of clothes today are cleaned by perc. A proliferation of cleaning franchises and dry-cleaning businesses offering fast service from convenient, clean, and attractive locations evolved to change the industry into what we see today.
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:
The following sections look at each of these steps in detail.
- 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.
- Pre-treatment - The cleaner looks for stains on your clothes and treats them to make removal easier and more complete.
- Dry cleaning - The clothes are put in a machine and cleaned with a solvent.
- Post-spotting - Any lingering stains are removed.
- Finishing - This includes pressing, folding, packaging and other finishing touches.
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.
A typical tag used by a dry cleaner
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.
Pre-treating stains is similar to the procedure used at home when you apply a stain remover to stains prior to washing them. The idea is to try to remove the stain or make its removal easier using chemicals. You can even help the process, especially if you catch the stain early! Simply apply water for wet stains (a stain that had water in it) and solvent for dry stains (a stain that has grease or oil in it). Then, gently tap and blot both sides of the fabric with a soft cloth so the stain "bleeds off" onto the cloth. Then, rinse the fabric, let it dry and your cleaner will do the rest.
If you don't know what to do when a stain happens, call your cleaner and ask him or her what to apply.
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.
Thanks to David Makepeace at Medlin Davis for allowing us to photograph the dry cleaning, washing and finishing equipment at the Cameron Village location.
Thanks to Micell Technologies for providing us with information on the liquid CO2 process.
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.
As an example, a typical machine might pump perc through the clothes at a rate of perhaps 1,500 gallons (5,678 liters) per hour. Perc is about 75 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 and then condensed over cooling coils. 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.
Cleaning plants using petroleum solvent rather than perc are exposed to a different set of circumstances and face some challenging considerations. The solvent is flammable, and therefore many fire-prevention steps must be taken for safety. The solvent is very slightly lighter than water and the two mix easily. There is also a need for higher temperatures to dry and deodorize the garments, which makes shrinkage and re-deposition of soil into the clothes more likely. These disadvantages are the reason why the industry currently uses perc almost exclusively.
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.
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-base 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.
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
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:
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!
- Applying steam to soften the garment
- Re-shaping it through quick drying
- Removing the steam with air or vacuum
- Applying pressure to the garment
A general purpose pressing machine
A special pressing machine for shirts: On the right is the sleeve press, and in the background you can see the press for cuffs and collars.
A perc dry cleaning machine
Washing machines for shirts and other laundered clothing: Shirts are washed in water rather than being dry cleaned.
The demand for environmentally safe products has increased in recent years as a result of government regulations and greater consumer awareness of environmental issues. Micell Technologies Inc. has developed a cleaning system, based on carbon dioxide (CO2) technology, that is an environmentally safe alternative to the traditional solvents.
Carbon dioxide is a naturally occurring substance, and at room temperature it exists in the form of a gas. In solid form, it is known as dry ice. Liquid CO2 has a gas-like consistency and a low surface tension, allowing it to function as a very effective cleaning medium when combined with detergents.
Liquid carbon dioxide can exist at room temperature only if extra pressure (several atmospheres) is applied to it. Micell's Micare system uses a conventional rotating basket with a detergent system. The system uses a 60-pound (27-kg) capacity MICO2 machine that contains liquid CO2 under pressure. It is similar to front-load mechanical-action machines and features gentle wash and extract cycles. The big difference is a heavy pressure door and the pressure chamber around the machine.
A detergent system (containing patented cleaning agents) enhances the cleaning ability of the liquid CO2, allowing it to remove soil from the garments. After the cleaning cycle, the machine pulls the mixture of liquid CO2 and cleaning agents away from the clothes and then cleans and re-uses the solution. This process does not require heating the garments, and therefore is gentle to the fabric.
For more information on dry cleaning and related topics, check out the links on the next page!
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About the Author
Nate Marks has been in the dry-cleaning industry since 1940. He has served dry cleaning organizations on local, state, and national levels as an owner, operator, and allied tradesman. Nate says he feels privileged to have worked with many of the pioneers in the dry-cleaning industry and to participate in its growth.