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An example of a discoloured aluminium pot washed in a dishwasher


Aluminium becomes naturally dull when washed in a dishwasher.

China or glass items, for example, casserole dishes may show dark (black or grey) discolouration.

This is not a fault with your dishwasher and a service visit cannot cure this problem

Please follow the steps below in order to attempt to avoid this problem from happening.

Usually the result of:

  • Natural oxidation of aluminium
  • Cutlery being allowed to scrape the surface, for example during mixing

Cause & Prevention


We usually find that discolouration of metal is simply natural oxidation. This is especially so with aluminium items which will become naturally dull over time if washed in a dishwasher.

Black marks, often found on china or glass is invariably the result of scraping metal cutlery or utensils against the surface.


There is no treatment for these issues and the damage is irreversible.


Do not wash aluminium items in the dishwasher.

Avoid scraping with metal implements.

Purchase cookware that is clearly marked as being dishwasher safe.

Pay attention to specialist items, such as cooking knifes, as many do state that they are unsuitable for washing in a dishwasher or that it is not advised.



  How You Can Get Help With Dishwasher Problems

To offer support in helping people to determine the cause of dishwasher problems please use the dishwasher support forum.

It’s fast, free, easy and normally someone will pick up on the post that can assist you often with a few experts chipping in if needed. Just register if you don’t have an account, we don’t mail you, send you spam or any of that stuff.

Post up your question and give images if you possibly can and the guys in the forums will do the rest for you and try to identify the problem you have.

Cost you nothing, might save you some embarrassment or worse, a charge for a service visit that wasn’t needed.

  Photographs Of Damage

If you can post photographs of the damage or problem you are having this can be really helpful in allowing the dishwasher technicians to see what the problem is.

The guys have the knowledge to assist with most problems but the more information you give them, the better they can help you.

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