Most manufacturers reformulated their dishwasher detergents after laws limiting phosphates went into effect last year.
Now Consumer Reports' preliminary tests find some detergents can leave glassware coated with a white film when washed in very hard water.
"Some readers wrote to us, complaining about film and buildup on their dishware," said Jim Nanni from Consumer Reports.
So Consumer Reports started investigating. Testers took a set of clean glass dishware and washed it using detergent and very hard water.
They ran the same set of dishes 20 times with the same detergent to simulate more than a month of dishwashing. Over time a film built up with some detergents.
With Method Smarty Dish, which otherwise is a very good cleaner, the glassware turned milky white after 20 washes. The dishes washed in Whole Foods 365 also developed a milky coating.
"This is a preliminary test," said Nanni. "We're going to continue to look into why some detergents left a film and others didn't."
Consumer Reports also ran dishwasher detergents through its standard food-cleaning tests. A mix of chocolate pudding, peanut butter and more is applied to plates and baked on. Macaroni and cheese is mashed on pots and baked on too.
Testers check to see how well the detergents clean up the mess.
Cascade Complete All-In-One ActionPacs was one of the best in Consumer Reports' cleaning tests. And in its test with very hard water, it did not leave a white residue behind.
Consumer Reports has some more tips to make your dishes sparkle.
- Use a rinse agent, which helps keep glassware spot-free, even in hard water.
- Avoid nesting silverware by placing some up and some down in the silverware basket.
- Make sure dishes faces the middle of the machine, angled downward.