The main cleaning agent is perchloroethylene, a solvent that dissolves oils and stains without water
Dry cleaners use a chemical solvent called perchloroethylene (often shortened to perc) to clean most clothes. Despite the name "dry cleaning," the process is wet — but instead of water, clothes soak in perc, which dissolves oils, grease, and many stains that water alone cannot remove. Perc evaporates quickly and leaves no water marks, which is why it works well on delicate fabrics like silk and wool that would shrink or lose shape in a washing machine.
Some dry cleaners use alternative solvents like hydrocarbon (a petroleum-based cleaner) or liquid carbon dioxide, especially if they market themselves as "green" or "eco-friendly." These work similarly to perc but have different environmental and health profiles. A few cleaners still use older solvents, though perc remains the industry standard because it is effective and relatively inexpensive.
The choice of solvent matters to you mainly if you have chemical sensitivities or care about environmental impact. Ask your cleaner which solvent they use — they are required to tell you, and the information is usually posted near the counter or on their website.
Key Takeaways
- Perchloroethylene (perc) is the most common dry cleaning solvent and works by dissolving oils and stains without water.
- Hydrocarbon and liquid carbon dioxide are alternatives that some cleaners use instead of perc, often marketed as more environmentally friendly.
- The dry cleaning machine agitates clothes in the solvent, then spins and heats them to remove the liquid before it is recycled.
- Spot treatment with pre-soaks and specialized chemicals happens before the main wash to target specific stains.
- Pressing and finishing use steam, heat, and sometimes sizing to restore shape and appearance after cleaning.
How the dry cleaning machine works
A dry cleaning machine looks like a large, sealed washing machine. Clothes go in, the solvent fills the drum, and the machine agitates them for 15 to 30 minutes — similar to a regular wash cycle but gentler and in solvent instead of water. The agitation loosens dirt and oils so the solvent can carry them away.
After agitation stops, the machine spins out the solvent (which is then filtered and reused), and then heats the drum to evaporate any remaining liquid. This drying step is crucial — it removes the solvent so your clothes do not smell chemical-heavy when you pick them up. The whole process, from start to finish, usually takes one to two hours per batch.
The solvent is not thrown away after one use. Dry cleaners filter and distill it repeatedly to remove dirt, oils, and other contaminants, then reuse it until it becomes too degraded. This recycling is why dry cleaning is expensive — the equipment to clean and store the solvent safely is costly, and the solvent itself is not cheap.
Spot treatment and pre-soaking for stubborn stains
Before clothes enter the main machine, dry cleaners inspect them for stains and treat problem areas by hand. This is where the real skill comes in. A stain spotter uses different chemicals depending on what caused the stain — protein-based stains (blood, egg) need different treatment than oil-based stains (grease, makeup) or tannin stains (wine, coffee).
Common pre-treatment chemicals include enzymes that break down protein, oxygen-based bleach for discoloration, and specialized solvents that target specific stain types. The spotter applies these by hand, lets them sit for a few minutes, then gently works them in with a brush or cloth. Some stains are pre-soaked in a separate tank before the main wash.
This step is why you should tell your cleaner about stains when you drop off clothes — the longer a stain sits, the harder it is to remove, and some stains set permanently if exposed to heat during pressing. A good cleaner will ask what caused the stain and how long it has been there.
Pressing, steaming, and finishing
After the solvent is removed and clothes are dry, they still look wrinkled and limp. Pressing restores shape and crispness. Dry cleaners use industrial steam presses — large machines with heated plates that explore steam and pressure to flatten fabric. For delicate items, they use a steam cabinet instead, which surrounds the garment with steam without direct pressure.
Some finishes require sizing, a starch-like chemical sprayed onto fabric to add body and crispness. Sizing is common on dress shirts, blouses, and some pants. It washes out when you launder the item at home, so it is not permanent. Your cleaner can adjust how much sizing they use — ask for light, medium, or heavy starch depending on how crisp you want the garment.
Collars, cuffs, and seams are often pressed by hand using smaller handheld steamers and pressing tools. This detail work is what separates a rushed cleaner from a careful one — it is also why rush orders cost more, because hand finishing takes time.
Why some fabrics need special handling
Certain materials cannot tolerate standard dry cleaning. Leather and suede are cleaned with specialized solvents and techniques because perc can damage them. Beaded or sequined garments may need hand cleaning or a gentler process because the stones can loosen or the backing can dissolve. Fur requires its own equipment and informed.
If your garment has a care label that says "dry clean only" but also lists restrictions (like "no perc" or "leather specialist only"), tell your cleaner. They may refer you to a specialist cleaner or decline the job if they cannot safely handle it. This is not them being difficult — it is them being honest about what they can do without damaging your clothes.
Some fabrics labeled "dry clean only" can actually be hand-washed at home, but that is a separate question. Your regular dry cleaner can advise whether a specific garment is safe to wash yourself, or whether it truly needs their solvent.
What happens to the solvent waste
Used solvent from the dry cleaning process is not poured down the drain. It is collected in tanks and either distilled on-site (if the cleaner has the equipment) or picked up by a waste disposal company. The solvent is then either recycled into new solvent or disposed of according to environmental regulations, which vary by state.
This is why dry cleaning is regulated more heavily than many other services — the solvents, especially perc, are hazardous chemicals that can contaminate groundwater if handled carelessly. Reputable cleaners follow strict protocols for storage, handling, and disposal. If you notice a strong chemical smell at a dry cleaner or see stains on the floor, that is a sign they may not be managing their solvent responsibly.
Frequently Asked Questions
Is the smell from dry cleaning harmful?
The smell comes from solvent residue. A small amount is normal and fades as you air out the garment. If clothes smell strongly chemical even after hanging them for a day, the cleaner may not have dried them thoroughly enough. Bring them back and ask them to re-dry. If you have chemical sensitivities, ask your cleaner to use hydrocarbon or carbon dioxide solvent instead of perc.
Can dry cleaners remove any stain?
No. Old stains, stains that have been heat-set (dried in a dryer or pressed), and stains from certain dyes or substances may be permanent. The cleaner will tell you if a stain cannot be removed — do not assume they did not try hard enough. Some stains can only be lightened, not erased.
Why do some clothes come back damaged from dry cleaning?
Damage usually happens because the garment was not suitable for dry cleaning (despite the label), the fabric was already weak, or the cleaner used too much heat or pressure. Always point out any damage when you pick up clothes — most cleaners have a time limit for claims, usually 30 days.
What is the difference between dry cleaning and wet cleaning?
Wet cleaning uses water with specialized detergents and gentler agitation, designed for delicate fabrics that cannot handle solvent. It is less common than dry cleaning but is growing. Some cleaners offer both and will recommend wet cleaning for certain garments.
Do I need to tell the cleaner about stains?
Yes. Point out stains and say what caused them if you know. The cleaner can then use the right pre-treatment chemical and avoid setting the stain with heat. Stains you do not mention may not get special attention and could become permanent.