What is a solvent, and why does water earn the title of “universal solvent”?
What is a Solvent?
A solvent is a liquid that dissolves other materials (solutes) to form a solution. Common examples include turpentine, ethanol, trichloroethylene, benzene, and, of course, water.
Chemists use the rule “like dissolves like.”
- Polar substances (like water) dissolve other polar materials (like salt).
- Nonpolar substances (like oil) dissolve well in nonpolar solvents.
Water is a polar solvent most of us use every day. Salt, also polar, readily dissolves in water, which is why oceans hold salt in solution.
Why Oil and Water Don’t Mix
Oil is nonpolar, so it doesn’t dissolve in water. Pour oil into water and it separates and floats. To dissolve oils efficiently, you need a nonpolar solvent. Historically, industry turned to chemicals like benzene because they cut grease quickly.
Benzene has been in use since Michael Faraday isolated it in 1825. After it was discovered, people found a variety of interesting uses for it, including as an aftershave lotion, and over time they recognized it as an effective solvent and degreaser. Benzene is very efficient at dissolving oils and pulling them off of the surfaces of industrial parts.
There’s only one problem: Benzene, like many other nonpolar solvents, is toxic to humans and the environment. The frequent use of benzene in industry resulted in many people becoming ill over time. The U.S. government banned the use of its pure form as a solvent decades ago.
In the mid-20th century, when scientists and workers began noticing links between nonpolar solvent use and health problems like leukemia and brain impairment, they began searching for alternative ways to effectively remove grease and dirt from industrial parts and other items without the same risks and dangers.
Water as the Universal Solvent
Water earns the label “universal solvent” because it dissolves more substances than any other liquid. People have cleaned with water for millennia. On its own, water won’t match legacy solvents for stripping heavy oils, but you can engineer the process to close that gap safely.
How Aqueous Parts Cleaning Works
Aqueous parts washers combine water with process enhancements to remove tough soils:
- Heat increases solvency and speeds reactions.
- Pressure and spray impact dislodge stubborn films and chips.
- Agitation or rotation moves a solution into threads, blind holes, and tight passages.
- Surfactants and targeted detergents help water lift oils and fine particulates.
This approach delivers powerful cleaning while avoiding exposure to many hazardous solvent vapors and difficult waste streams.
AEC Systems’ approach
At AEC Systems, we design parts cleaners around your parts and soils. After we understand your cleanliness targets, geometry, workflow, and space, we recommend a washer that applies the right mix of mechanical action, water, heat, and compatible detergents. Our goal is to meet your spec reliably and efficiently without relying on harsh solvents. If you need help selecting chemistry, we can connect you with reputable suppliers.
If you have parts that must meet a defined cleanliness spec, contact us to discuss an aqueous cleaning solution built around your parts, your process, and your facility.