The manufacturers of our left-handed kitchen knives claim they are dishwasher safe and that the handles and blades will not be harmed by putting them in a dishwasher. We test this ourselves and regularly dishwash the knives we use use in our own kitchen and have not had any problems. However, we do get occasional reports from customers of small rust spots developing on their knife blades so we have looked into this and found out the following:
- Dishwashers can sometimes cause rust spots on stainless steel surfaces because of a combination of the levels and types of salt, rinse-aid and dishwasher tablets used.
- The biggest factor seems to be having too high a level of salt in the machine, particularly when using multi-function tablets that can contain salt themselves as well as what you put separately into the water softener.
- There are such a huge variety of dishwashers, cleaning programmes and consumables as well as large variations in the softness of local water that it is very difficult to give a single recommendation on how to avoid it.
- Reducing the rate at which your machine uses salt, while still cleaning effectively, is a good thing to do anyway and the manual for your machine will tell you how to adjust the flow rate.
- Removing the knives from the dishwasher soon after it finishes will also help, as being in the steamy damp environment for a long time can also cause rust spots.
- Rubbing the knife blades with a slice of lemon occasionally can help reduce the problem.
- If you do get rust spots, they should be easy to remove with a scourer, a stainless steel cleaner or with some car chrome polish.
It does seem this can happen to any stainless steel if there is a combination of the factors above so we cannot absolutely guarantee that our knives will never develop rust spots under any conditions and you may need to adjust the salt usage or other factors in your dishwasher to avoid it happening.