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What specifically about a dishwasher is damaging to cookware?

Like say an all-clad all-stainless exterior pan?

I could see enamel-coated getting etched or banged up on enamel coated cast iron. Obviously things like carbon steel and cast iron shouldn't go in dishwashers.

How do stainless and nonstick get damaged in the dishwasher short of getting banged up when hitting other items? I also hear this about knives. I have stainless wustof knives, and while I never put them in the dishwasher (too easy to clean by hand and I can't guarantee they won't hit stuff), is the only reason not to put stainless knives in the dishwasher besides the possibility of dulling the edge due to mechanical damage?

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  1. Two things come to mind, first mechanical banging around and second and perhaps most importantly the detergent used in a dishwasher is tough on metals of all types.

    With regards to the knives, it would be the same thing, mechanical damage banging around with the water jets, but the detergent is also tough on the very fine edge of a knife.

    1 Reply
    1. re: mikie

      I can tell you one pass through the dishwasher ruined 2 of our non-stick pans, not only didn't they work even the finish was noticeably different, i've heard the same thing about the car wash chemicals(the automated ones) dulling the clear coat.

    2. Non-stick cookware should not be cleaned in the dishwasher. The detergent is too harsh.

      As for other items, I have read that the reason they suffer in the dishwasher is because we tend put them in too "clean". Since the detergent is looking for something to wash off, it will attack the finish of plates and cookware if there is no grease, food, etc. to clean. Instead of prewashing, just put your stuff in there as is.

      1. So there's actually chemical damage occurring in the dishwasher? I understand that the detergent is rough on finishes, but is it actually damaging? I can't imagine that barkeepers friend is less tough on my all-clad than the dishwasher.

        If all of these pans shouldn't go in the dishwasher is the reason that the manufacturers say that the pans are dishwasher safe is to sell more?

        2 Replies
          1. re: LaureltQ

            Yes, the detergent is caustic and damaging. Dont use it to handwash stuff,it will hurt your hands too.

            Barkeepers friend is nothing more than oxalic acid, which, while abrasive, is a normal part of cooking. Heck, I've precipitated it out of kale before! (and it is not caustic at all)

          2. Dishwashing detergents are being made with less phosphates to help the environment and not cleaning as well.
            http://www.nytimes.com/2010/09/19/sci...

            1 Reply
            1. re: monku

              In Canada they pulled all the phosphates out, now i'm looking for a water softener just for the dishwasher, 3 passes through everything was covered in a white haze , now i'm putting in a quart of vinegar at the last rinse to stop it , and filled the jet dry dispenser with vinegar as well

            2. Hi LaureltQ,

              I agree with Mikie. The detergents used for automatic dishwasher are usually much harsher than the one we use by hand. That said, my impression is that these stainless steel cookware will not be permanently damaged by them. A bit of stain maybe, but nothing cannot be fixed. Now, anodized aluminum cookware is a completely different matter.

              6 Replies
              1. re: Chemicalkinetics

                I couldn't believe what it did to my aluminum parts for my meat grinder , destroyed the finish

                1. re: Dave5440

                  Yeah, aluminum is much more reactive than stainless steel. I can totally see that. Probably worse for anodized aluminum than bare aluminum because the anodized surface can be striped off.

                  So what did you do after that incident? Were you able to fix the part by sanding the affected surface or buy new parts?

                  1. re: Chemicalkinetics

                    I ended up buying a new grinder, the motor was starting to smoke on it anyway, and any SS i've ever put in (or left in not intending to run it) has never been affected

                2. re: Chemicalkinetics

                  This is what I imagined was the case. I can't imagine that there would be permanent damage to SS cookware. I have a junky nonstick pan my mother in law bought us when my hubby and i started dating that has probably only been washed in the dishwasher and it is still in great shape after 5 years. Perhaps that has more to do with how often I use it versus other pans than how it stands up to the dishwasher.

                  1. re: LaureltQ

                    I agree. All Clad (like many others stainless steel manufacturers) claims their Stainless Steel cookware are dishwasher safe:

                    http://www.all-clad.com/consumer-serv...

                    I just looked up the All Clad website (as you can tell above) and surprised to find out that All Clad has made a new line of anodized aluminum cookware which can endure the dishwasher environment. Evidently, All Clad put another layer of "something" to protect the anodized aluminum. Here: "The revolutionary exterior coating technology allows LTD2 to endure the harshness of daily dishwasher":

                    http://www.all-clad.com/collections/L...

                    Finally, my vauge understanding is that the newer dishwasher detergents have gotten less aggressive in recent times.

                  2. re: Chemicalkinetics

                    It seems that I have seen kind of an iridescent dark blue damage to a stainless pan at sometime, with something washed in the DW. I can't remember the exact circumstance. Maybe my mom's pans. Would a copper bottom contribute to that? I do wash my KA stainless mixing bowl with no problems, but wash most all pots and pans by hand, do to that memory.