White Marks On Glass From The Dishwasher

[kgt]

What causes Glass to come out of the dishwasher with a white coating on it? And how do you stop this happening?

[theprof]

The principal cause of this is a chemical reaction between the harsh phosphate salts contained in the dishwasher tablets/powder/sachet and the glass.

The glass is being etched by the phosphate and the reaction is irreversible - it's not possible to restore the glassware to the original condition without involving specialised polishing etc.

There is a slim possibility that if you are living in a hard-water area, the deposit may be due to insoluble calcium salts deposits. To test this, place a filmed tumbler on it's side in a shallow dish of undiluted white vinegar and leave it undisturbed for a couple of hours. After the elapsed time, look at the glass carefully in a good light.

If the coating has disappeared on the immersed side, the problem is due to lime in the water and you should then follow the dishwasher manufacturers water-softening advice.

If the coating is still present, it's permanent phosphate damage.

My wife now makes sure that she only buys good-quality dishwasher proof glassware which has solved the problem for us, although I would add we're fortunate to live in a reasonably soft-water area.

You could also try changing your dishwasher tablets. A lot of the more heavily advertised ones are undoubtedly better at cleaning, but are also harsher to the glassware due to their high phosphate and other ingredient content.

The wife's just told me that Fairy Active Bursts are her current favourite!

Finally, whatever you do, make sure you never put your lead-crystal in the dishwasher.