A: There can be several reasons drinking glasses wind up looking cloudy after a cycle in a dishwasher.
One is hard water, a term that originally came from the fact that the high concentration of calcium, magnesium and sometimes other metals in this water made it hard to wash things, according to the Water Quality Association, a trade group for water-treatment companies. Instead of lathering and keeping soil suspended in the wash water, soap in hard water develops into what the association’s website calls “curdy precipitate.” Instead of rinsing away, some of the minerals in the water end up deposited on glasses, making them look cloudy.
Ironically, soft water can also cause glasses to cloud, although this was more of a problem when dishwasher detergents were formulated with phosphates. Combined with very hot water, the phosphates could change into a form that would actually eat into glass, causing etching that’s impossible to remove. Phosphates helped dishwasher detergents cut through food crud, and they helped remove calcium and kept the cleaned-away food from resettling on the dishes. But the phosphates stayed in the wastewater and caused algae blooms in waterways and hurt marine life. By 2010, local, state and federal regulations forced manufacturers to remove phosphates from dishwasher detergents.
Without phosphates, dishwasher detergents still remove food, but they aren’t as effective in keeping the loosened food and minerals in the water from resettling on glasses and other dishware. Rinse aids are the answer to that. They contain surfactants, which keep loosened soil suspended in water, and chelating agents, which keep mineral deposits from forming. And they make water sheet off, rather than form droplets, which can leave dots of minerals after the water evaporates.
Why your glasses would suddenly start looking cloudy could be because deposits or etching that started forming long ago have finally built up to a level that’s more noticeable. Or perhaps you changed dishwasher detergent, or the manufacturer of the detergent or rinse aid changed its formula. Try soaking one of your cloudy glasses in vinegar for about five minutes. Then scrub or wipe vigorously with a nonabrasive pad or cloth, and rinse. If the glass still looks cloudy, it is probably etched — permanent damage that has no remedy.
But if you’re lucky, the test glass will be clear. Rather than fuss over each piece to remove the cloudiness from the rest of your collection, try a procedure that Cascade, a manufacturer of dishwasher detergents and rinse aids, recommends: Put two cups of white vinegar in a bowl and place on the bottom rack of the dishwasher. Run the glasses (and dishes, if any of those look dull or cloudy) through a cycle with no detergent. Rewash with dishwasher detergent to remove residual vinegar. Do not add metallic items to the dishwasher for the vinegar treatment.
Once you get the glasses clear, consider switching to a different detergent or rinse aid. Consumer Reports tested dishwasher detergents and, in a March report, found that detergent packs — also labeled as pacs, tablets and tabs — generally work better than gel detergents. Not only do they contain a measured amount of detergent, but they also generally contain a rinse aid. The top-rated detergents in tests by Consumer Reports were Member’s Mark Ultimate Clean Dishwasher Pacs ($23.95 for a tub of 105 tablets on Amazon) and Cascade Platinum ActionPacs with Dawn (available at most supermarkets or on Amazon for $19.99 for a tub of 70 tablets). Cascade’s website says its dishwasher packs are formulated with water softeners to help prevent hard water deposits on your dishes and, in many cases, eliminate the need for a rinse aid.
If you’d rather use a powder or gel detergent, use a rinse aid. Ingredients aren’t all the same, so consider switching to a different brand.
Cascade also recommends using water that is at least 120 degrees. Check the setting on your water heater, and consider running hot tap water before starting the dishwasher, although this wastes water.