Why does my dishwasher leave a white film on glasses?

Cloudy glassware generates more bad advice than almost any other appliance problem, because the two causes need opposite corrections. Limescale is mineral deposited on the glass by hard water and it needs more softening. Etching is the glass surface itself being dissolved, and it needs less aggressive washing. Treating etching as limescale — more salt, more descaler, hotter cycles — makes it worse permanently.

What you'll need

• White vinegar or citric acid
• A glass you can sacrifice to the test
• Dishwasher salt (optional)
• A fridge or kettle descaler (optional)

Step by step

1. Run the vinegar test on one affected glass.Fill or submerge it in neat white vinegar for ten minutes, then rinse and dry. This is the only reliable way to tell the two causes apart, and it takes ten minutes.
2. If the film came off, treat it as limescale.Hard water minerals dried onto the surface. Everything from here is about softening the water and improving the rinse — see the next four steps.
3. Check the salt reservoir and the machine's hardness setting.An empty reservoir or a hardness setting left on the factory default in a hard water area is the commonest cause. Fill it with proper dishwasher salt and set the hardness to match your water company's published figure.
4. Increase or start using rinse aid.It makes water sheet off rather than bead. Droplets that sit on the glass and evaporate leave their entire mineral content behind as a spot; water that runs off takes the minerals with it.
5. Descale the machine itself.An empty hot cycle with a dishwasher descaler or citric acid clears scale from the heating element, spray arms and pipework. Scale in the arms narrows the jets, which makes the rinse less effective, which deposits more scale.
6. Clean the spray arm holes and the filter.Push a cocktail stick through each hole. A partially blocked arm gives an uneven rinse, and the areas that get less water are the ones with the worst film.
7. If the glass stayed cloudy, treat it as etching — and change course completely.Etching cannot be reversed. Nothing polishes it out and no product removes it. Everything from here is about stopping it happening to the rest of your glassware.
8. Reduce the softening rather than increasing it.Water that is too soft is corrosive to glass. If you have a whole-house softener, turn the machine's own hardness setting to its lowest and stop adding salt. If the machine's hardness setting is set higher than your actual water, bring it down to match.
9. Wash glass at a lower temperature and reduce detergent.Use the glass or delicate programme at 40-45°C. Use half a tablet, or a powder dosed to the load, rather than a full tablet for a small wash. High alkalinity plus high temperature is the combination that dissolves glass surfaces.
10. Move genuinely valuable glass out of the machine.Thin crystal, hand-decorated glass and anything with a gilt rim will not survive a dishwasher indefinitely at any setting. This is the honest answer rather than a setting change.

Common mistakes

• Adding more salt to fix etching — Etching is caused by water that is already too soft or too aggressive. More softening accelerates the damage, and every affected glass is permanently ruined.
• Assuming a vinegar rinse aid habit is harmless — Repeated acid exposure is hard on rubber door seals and hoses. Use it for the diagnostic test and as an occasional descale, not as a permanent rinse aid substitute.

If it doesn't work

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