So my aunts were over last week and being perfectly well-intentioned, helped me clean up the kitchen and ended up putting my 8” aluminum cake pan in the dishwasher.  It’s your standard heavy cake pan, I think from William Sonoma.  The next morning when I was emptying the dishwasher, I saw the cake pan—it was a darkish color, and almost seems to have some pitting in it.  I wiped it and wiped it with a paper towel and the black stuff kept rubbing off.  Is it ruined?  And why would putting it in the dishwasher cause such a reaction?

Loopy - 04 May 2011 12:56 AM

So my aunts were over last week and being perfectly well-intentioned, helped me clean up the kitchen and ended up putting my 8” aluminum cake pan in the dishwasher.  It’s your standard heavy cake pan, I think from William Sonoma.  The next morning when I was emptying the dishwasher, I saw the cake pan—it was a darkish color, and almost seems to have some pitting in it.  I wiped it and wiped it with a paper towel and the black stuff kept rubbing off.  Is it ruined?  And why would putting it in the dishwasher cause such a reaction?

I have historically put all of these pans in the dishwasher.  I’ve never seen pitting, but others here have reported it.  The pans do get a film of what I assume to be aluminum oxide on the surface.  It will wipe off after you go through a number of paper towels and maybe the blue type scrubbing pads; the pans certainly aren’t ruined, unless you have aluminum coated steel, then “maybe”.  I have since stopped putting the uncoated aluminum in the dishwater, since the effort to scrub off the film is greater than cleaning them.

(BTW, I think the Williams Sonoma stuff is aluminum coated steel; I won’t buy those anymore because the steel can rust beneath the aluminum.)

All is not lost- I don’t think. I would suggest Bon-ami and scrungy pad.  Bon-ami is safe, even on glass and corning(which is what it was developed to clean originally, I think), so it won’t scratch. It’s available at many grocery stores next to other powdered cleansers. Another alternate is to try a 400 or 600 grit sandpaper, which can be wet to further soften it’s effect. I had to use 400 once on a copper cookware piece who’s interior didn’t hold up to the hot oil I fried in it. It was discolored and pitted, but it did come back with a little elbow grease.
Your incident makes me think I do the right thing by only allowing ME to clean up after myself- no one else does it to suit me- and I don’t have a dishwasher- except me!

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My understanding is that residue is iron oxide caused as a result of the interaction between the dishwashing cleansers and the pan’s aluminum surface.

I had the same reaction a few months ago on my aluminized steel cake pans from Williams-Sonoma.  I was intrigued because it hadn’t happened before to such an extent.  What I learned is that recently, by law, all brands of dishwashing detergents were changed to remove phosphates—environmental toxins which can harm the water supply.  One of the benefits of phosphates was that they protected against oxidation in the dishwasher.  Without the protection of the phosphates, more iron oxide is formed and more residue is left behind.  One way to clean the pans is with a solution of warm water and cream of tartar, but it takes a lot of washing and rubbing.  I decided it wasn’t worth it and switched to the GoldTouch pans from Williams-Sonoma.  I did accidentally put one in the dishwasher, and it was fine.  I also regularly run my non-stick Bundt pan through the dishwasher with no ill effects.  However, I am sticking to handwashing my cake pans from now on!

epicat - 05 May 2011 12:40 PM

My understanding is that residue is iron oxide caused as a result of the interaction between the dishwashing cleansers and the pan’s aluminum surface.

Iron oxide is what we call “rust” and is orange-ish.  Since it only forms on iron, it wouldn’t form on aluminum.  For the aluminum-coated steel pans, in areas where the aluminum is thin or flaked off, iron oxide can form, since steel has a large iron component.

Thanks for the responses….they all make perfect sense.  A small amount of water had also pooled on one of the sides where the pan was resting (upright), and there was a little rust there as well.  So, oxidation + effects of dishwashing detergent are my answers.  Will try the cream of tartar and other cleaning solutions mentioned and keep at it with the paper towels.  I once baked a white cake in a pan that had this stuff on it and I hadn’t realized it, and the cake actually came out with it on the sides, so I had to do a serious trimming job.  Hmm, maybe I should bake a cake mix cake in it and see if it cleans off the last of it : )