Why your glasses come out of the dishwasher cloudy
Updated August 2026
Short answer: it depends on which side of the lake you live on. On the Northshore the culprits are a silica film and permanent etching from detergent working on very soft water. South of the lake, the river water is genuinely harder, and cloudy glasses are usually mineral spots. Here is how to tell the three apart and what actually helps with each.
Film or etching? The ten second check
Hold the glass under running water. A surface film changes its look when wet and comes back as it dries. Etching looks the same wet or dry, because the roughness is in the glass itself. Film also tends to be patchy while etching is a uniform haze across the whole glass.
Why soft water makes etching worse
Dishwasher detergent is strongly alkaline. In most of the country, hardness minerals in the water blunt its attack. Northshore water tests soft, in the single digits, so the detergent hits your glassware at full strength, cycle after hot cycle, and slowly eats the surface. Appliance makers like Miele and GE document this exact problem, and once etching starts it is permanent.
When it really is hard water
South of the lake the story flips. Metairie and Kenner run about 98 milligrams per liter of hardness, the Westbank about 81, because Mississippi River water carries minerals the Northshore's aquifers never pick up. When that water dries on a glass, the minerals stay behind as white spots and streaks.
The test is a five-minute soak in white vinegar. Mineral spots dissolve and the glass comes out clear. Film and etching stay put. If vinegar clears your glasses, you have a hardness problem, and this is the one version of cloudy glassware a water softener actually fixes, dishwasher included. We wrote up the south shore numbers in is Metairie water hard.
No filter prevents etching, ours included
A water system is the wrong tool for etching, no matter who sells it. What actually protects your glasses costs nothing:
Use far less detergent. In soft water a teaspoon usually does the job, and most people use several times that. Scrape instead of pre-rinsing. A little food soil actually buffers the detergent. Run cooler cycles and skip the sanitize setting and heated dry for glassware. Always use rinse aid. And hand-wash the glasses you love, because thin and older glass etches fastest.
Where reverse osmosis genuinely helps
An under-sink RO system takes the silica and dissolved solids out of the water at your kitchen tap. Drinking water tastes clean, and glasses you rinse at that sink dry without a spot. It will not reach your dishwasher or shower, since those run on separate plumbing.