When seeking out a budget dish soap (or any cleaning agent), you might assume bright colors and intense smells are part of the deal. Not so with our $ winner, Seventh Generation’s Free & Clear Dish Liquid Soap. For anyone skeptical about eco-friendly cleaning products, this “powered by plants” dish soap held its own against more recognizable names like Dawn, Gain, and Ajax in our testing, with nary a harsh ingredient in sight.
To find out more about the chemistry of kitchen cleanliness, we tapped Robert D. Tilton, PhD, a professor of chemical engineering at Carnegie Mellon University, to help us figure out what exactly makes an effective liquid dish soap. Right off the bat he mentioned that the products used to clean pots, pans, dishes, and silverware are technically detergents, not soap. While that’s true, the reality is you’re probably not gonna stop calling it dish soap, so we’re going to follow suit for the rest of this review.
Still, it’s worth knowing the difference, if only to understand how this stuff works — which brings us to the chemistry lesson portion of our review. Safety goggles on!
In a nutshell, the distinction between soap and detergent comes down to special types of chemical molecules called surfactants. While that sounds like something you might catch at the beach, it’s actually a portmanteau of the words “surface active agent.” Basically, surfactants help lower the surface tension between two liquids to help them play nice with each other. Dish detergents contain highly precise surfactants that allow water to bond, trap, and loosen oil and grease. Combined with scrubbing, this is what gets the grime off your dishes and ultimately down the drain.
Unlike, say, bar soap, dish detergent doesn’t accommodate for the naturally occurring oils that keep skin healthy. And because soaps are made with certain fats and oils, they react with minerals in water entirely differently than detergents do, often leaving a residue (aka soap scum). All of which to say, you wouldn’t want to use bar soap on your floor, laundry, or dishes. And unless you hate your hair, you wouldn’t want to use dish soap as shampoo. Each product is made with very specific function in mind.
And that concludes our mini chemistry lesson. Your assignment is to go forth and kill at trivia night. Safety goggles off.
Now, without going beyond the scope of this review, dish soaps contain many surfactants, and they all have different purposes. “There is a phenomenon known as synergism, which means that the combined action is greater than any one acting on its own,” Tilton told us, meaning one surfactant might be good at one part of the cleaning process, like foaming, and another might be better at dispersal. Together, you get a more powerful dish soap ready to take on your entire post-BBQ dirty-dish haul.
One of the most common surfactants found in dish soap, sodium lauryl sulfate (a major grease killer), is often derived from petroleum, but in the case of Seventh Generation’s line of Free & Clear products, it’s sourced from coconut and palm kernel oil — essentially the stuff that makes it plant-based and biodegradable. This dish detergent also contains other plant-sourced surfactants, like lauramine oxide, known for its foaming properties.
When we tested Seventh Generation Free & Clear against other similarly priced dish-washing liquids like Ajax and Gain, it held its own. Remember how surfactants help water bond, trap, and loosen oil and grease? Our team spread a teaspoon of vegetable oil onto plates and submerged them in soapy water to see how effective each brand was at removing oil without scrubbing, and Seventh Generation imparted a visible reaction, rapidly dispersing the oil off the plate.
For our second test, we left the measuring equipment and pipettes behind and took to the BuzzFeed cafeteria post-lunch, hand-washing stacks on stacks of dirty dishes. We went to town on stuck-on sauces, salad dressings, and grease from who knows what, and Seventh Generation immediately stood out from the pack not only for its cleaning power, but also for its lack of overpowering synthetic aroma.
If you’re looking for another budget option, Dawn Ultra was our runner-up in this price range. Even though Seventh Generation and Dawn Ultra offered nearly identical cleaning power in our tests, we chose Seventh Generation because the Free & Clear line is hypoallergenic and scent-free. Another big thing: Seventh Generation products aren’t tested on animals! To find these qualities in a dish soap at such a low price point without sacrificing cleaning power makes Seventh Generation’s Free & Clear the obvious winner.