Fix
Why does glassware get cloudy? Hard-water film versus permanent etching, how to tell them apart, how to clear the haze and how to prevent it.
A glass that comes out of the wash looking foggy is usually suffering from one of two very different problems, and only one of them can be fixed. The first is a film of dried minerals sitting on the surface; the second is etching, where the glass itself has changed. A quick look at how the haze feels tells you which one you have before you spend time scrubbing.
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Water counts as hard when it carries a lot of dissolved minerals such as lime and calcium. Droplets left on a glass straight from the dishwasher dry out, and the minerals stay behind and build up into the telltale fog.
The other cause is the wash itself. A dishwasher can permanently alter the glass surface, and that damage does not wipe off.
Detergent residue adds to both. Cloudy drinkware is often down to detergent buildup, etching or hard water, sometimes all three.
Etching is lasting damage to the surface from minerals, abrasive scrubbing or harsh dishwasher cycles. It shows up on expensive crystal and cheap glassware alike. For what sets crystal apart from ordinary glass, see understanding crystal glass.
Softened water is a common trigger, because detergent and heat act on glass differently when the water has no calcium or magnesium in it. Taking glasses out right after the cycle ends avoids the high heat of the drying phase, which speeds etching up.
Feel the glass before deciding on a fix. A few simple signs separate a deposit from damage.
White vinegar is acidic, so it dissolves hard-water minerals. Before soaking valuable pieces, check the maker's care instructions, since crystal and decorated glass can have their own rules.
Hand washing is the surest protection, since it removes the dishwasher from the picture. Dishwasher sets exist too; the Villeroy & Boch Boston Pearl glasses are listed as dishwasher safe on the top rack only.
If vinegar, soap and a dedicated glass polish all fail to bring the clarity back, the glass is probably damaged for good. For items where clarity matters, replacing the etched pieces is the practical answer. For replacement sets, see our recommendations on which luxury glassware brands to buy.