There are two primary reasons for cloudy glasses: white film from hard water and from etching.
Wash the glass in a bowl of vinegar. If the cloudiness disappears, then the cloudiness was caused by hard water. If the cloudiness does not disappear, it was caused by etching.
White film from hard water:
- Adjust the amount of detergent used in the dishwasher by using less. The amount may vary so some experimentation may be needed depending on the level of water hardness.
- Be sure to use a good quality rinse aid
- Etching is caused by glass surface erosion from heat exposure and contact with acidic solutions. It is permanent.
- Etching can possibly be prevented by not pre-rinsing or pre-washing dishware, using a light wash cycle for glasses and using the correct amount of detergent (not more than needed).