Aluminum Pans

I've noticed that whenever I put my aluminum cake pan and baking sheet in the dishwasher, it gets a chalky, grey residue that comes off on your hands. It concerns me that this isn't safe (I scrub it off by hand before using). Does anyone know what this film is, and why a dishwasher brings it out?

Amanda Hesser


Andrew T. June 20, 2017
If you are looking to re-shine the pan, here is a video w/ a method to re-shine the aluminum using oven as long as the pans fit in a roasting pan. no scrubbing needed w/ cream of tar tar.
Sam1148 March 1, 2012
I think the chalky powder mentioned is in fact soap residue, as the Aluminum reaction described is more of a dark stain.
I get that powder stuff every few months and then clean the machine while empty with the vinegar. Mostly the powder is on the black plastic handles of steak knives and teflon pans. Sometimes it's just over crowding or a large pan blocks the upper arm of the dishwasher---still the vinegar cure is good to do just as a matter of course for a dishwasher.
Now, I'm going to have to look and see if the stuff I'm using is phosphate free.
SKK March 1, 2012
Residue not healthy and what takes it off is soaking in vinegar of lemon juice.
I find that I only get that layer on the bottoms of my pans. I thought maybe it was somehow related to contact with the gas flames, but this sounds like a much more plausible explanation. I think I will also start handwashing....
Helen's A. February 29, 2012
That's why I don't put my aluminum pans in the dishwasher - always hand wash...
Greenstuff February 29, 2012
Here's what NPR had to say about it
Droplet February 29, 2012
I have a small knife that belonged to my grandma. It's simple and appeared to be made of one kind of metal, but somebody made the mistake (unknowingly) to put it in the dishwasher. The handle of it, made of aluminum, deteriorated very rapidly and turned from somewhat shiny to very dull and powdery, as if acid damaged surface. I asked my uncle about it because metals are his area of exeprtise and he took it with him to give the handle some kind of a bath in order to prevent future deterioration. So I believe the reaction is indeed unsafe because it indicates a bare aluminum surface.
cranberry February 28, 2012
Yes, there is a chemical reaction that happens that blackens or greys the aluminum pans. I had this happening even with phosphates in the dish detergent, so it's not that.

Note this will also happen if you use certain cleaners on brushed aluminum fixtures - our light fixtures and some window trim were ruined this way - they are completely grey and smudged looking and there is no way to repair it. I believe it is products that contain ammonia, like windex, but I'm not sure. Someone else was cleaning for me for a few months, and I'm not totally sure what was used.
Sam1148 February 28, 2012
It may be time to clean your dishwasher. Some materials hold on to soaps that tend to hang around in the dishwasher. Especially if you have hard water. You'd be surprised how much soap that hangs about in the dishwasher. (I've taken my apart before--surprise!)

To clean it run it on a short wash cycle empty and add a few cups of white vinegar. That will dissolve most soap residue. Rinse, and repeat, rinse again with out the vinegar.
Amanda H. February 29, 2012
Thanks for this tip -- going to do it this weekend.
Greenstuff February 28, 2012
EmilyC has the story. This started to happen when the formulations of dishwasher detergents were changed to remove phosphates. The changes and its effect on aluminum were not publicized, but here's one NYT article: . I have a few cheap knives with aluminum handles that I routinely put in the dishwasher, and they suddenly turned black. They are the only aluminum I continue to wash in the dishwasher.
pierino February 28, 2012
I never, ever put my serious pans in the dishwasher, aluminum or not. Same deal with knives.
EmilyC February 28, 2012
I agree with Darlene -- you're best off hand washing your aluminum. In general, the chemicals in automatic dishwasher detergents are reacting with the aluminum, resulting in discoloration and the grey residue you're seeing. In the last few years, many companies have reformulated their detergents (for example, due to many states banning the use of phosphates in dishwasher detergents) and are continuing to tweak them, so that's why you may be experiencing this for the first time, regardless of whether you've switched brands.
Mr_Vittles February 28, 2012
That sounds like soap scum to me. But as others, above have said, Its probably not good for you. In general, I avoid aluminum as a cooking material. Its reactive, and the thought of eating metal (even at the atomic level), does not appeal to me.
Darlene C. February 28, 2012
I've had this happen as well. Asked friend/chemist, and the conclusion was that the gray film is something called atomic hydrogen. It is basically the dishwashing soap interacting with the aluminum, that causes the metal to flake. Also, the high heat of the dishwasher accelerates the reaction.

Basically, I was told to hand wash aluminum items...

Hope this helps.
Panfusine February 28, 2012
I found this explanation via google..
nutcakes February 28, 2012
Very interesting and lengthy discussion. Bottom line for me is don't put your aluminum pans in the dishwasher.
bigpan February 28, 2012
I've not experienced this, but wonder if it is caused by the detergent you use. Powder or liquid? Maybe try a different brand to see what happens.
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