The short answer

Dry cleaning works by using a non-water solvent to remove stains, oil, and dirt from clothing.

The long answer

The first thing you should know is that dry cleaning is not dry. Dry cleaning just doesn't use water as a solvent to lift grime up off of your clothing, like you would at home.

Why is water an issue for some fabrics? Water causes fabric fibers to swell which sometimes results in clothing losing color, shrinking, or becoming misshapen. Additionally, since oil is insoluble in water, oil-based stains can't be fixed with a water solution. Thus, "dry" cleaning.

When dry cleaning was first invented, kerosene and gasoline were used as cleaning agents. However in the 1930s the industry switched to using a more stable, less flammable synthetic solvent called perchlorethylene, or "perc" for short. Unfortunately perc is now known to cause cancer to dry cleaning workers and even residents of buildings adjacent to dry cleaners. More and more, the industry is shifting away from perc to using safer solvents and methods.

Here's the basic three-step process dry cleaners use:

1. Pre-treatment: During this phase, the dry cleaner will inspect your clothing for any stains and apply a stain removal agent or steam gun to help clean them.

2. Dry cleaning: Next the clothes will be placed in a dry cleaning machine, where a liquid solvent works to clean the clothes. The solvent gets filtered throughout the process and then is distilled, purified, and reused in the next load.

3. Post-treatment: Also called "post-spotting," in this phase the dry cleaner removes the clothes from the machine and inspects them for any lingering issues. Interestingly, just as some stains cannot be lifted with a water-based solution, other stains cannot be lifted without water. The dry cleaner will carefully use a water-based solution to remove any final issues.

🧠 Bonus brain points

I've seen dry cleaners market themselves as "organic" or "green". Are those safer for the environment and health of workers?

Green dry cleaning refers to any dry cleaning that does not use perc as its cleaning solvent. But there are plenty of perc alternatives which aren't typically what you as a consumer would think of as "green" or "organic."

For example, a common alternative are other petroleum-based solvents. These are called "organic" because they contain carbon. But since it's a byproduct of gasoline manufacturing, it certainly raises questions about its environmental impact.

Other more environmentally and health-conscious green dry cleaning methods include "wet cleaning" (more specialized cleaning using water), liquid carbon dioxide cleaning, and silicon-based solvent cleaning. If you're curious about which method your dry cleaner uses, it doesn't hurt to ask.

Sources

Classic Drycleaners and Laundromats. (2021, October 22). How Does Dry Cleaning Work?. Classic Drycleaners. https://www.classicdrycleaner.com/what-is-dry-cleaning

Earnest, G. S., Beasley Spencer, A., Smith, S. S., Heitbrink, W. A., Mickelsen, R. L., Ewers, L. M., &; McGlothlin, J. D. (1997, December). Control of Health and Safety Hazards in Commercial Dry Cleaners: Chemical Exposures, Fire Hazards, and Ergonomic Risk Factors. Centers for Disease Control and Prevention. https://www.cdc.gov/niosh/docs/97-150/default.html

Marlowe Leverette, M. (2022, September 13). How to Find Eco-Friendly Dry Cleaners. The Spruce. https://www.thespruce.com/what-is-green-dry-cleaning-2145936

SGS Group Management SA. (2017, August 8). Green Dry Cleaning Solvents. SafeGuardS. https://www.sgs.com/en/news/2017/08/safeguards-12417-green-dry-cleaning-solvents