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Why did my pot get so blackened after boiling some eggs?

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By: Kroltan All content is licensed under CC BY-SA
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Q: Why did my pot get so blackened after boiling some eggs?

I bought this pot a few weeks ago. I've only used it a couple times since, but yesterday I decided to boil some eggs in it.

I ended up forgetting about them for a minute, when I came back the water was not enough to cover them anymore. About 10% of the eggs surface were exposed to air, however, the pot was this very dark color.

I've never seen a pot blacken like that, at most something like a kettle if you let it run dry for a while.

The pot has what looks like a machined bottom, with some casting bubbles that you can see as the light spots at the bottom. Which leads me to believe this might have been caused by scrubbing, given the strange uneveness? But the coloring only manifested once I used it again.

By weight, and the fact it is so poorly cast, I think it might be aluminium, but there are no markings specifying the material of the pot. I even went back to the store and the label doesn't specify either.

Answer

Uncoated aluminum pans are very prone to oxidization. Aluminum Oxide can be dark grey, or get close to black. Certain things can make aluminum oxidize faster, such as putting them through the dishwasher.

This is pretty common in uncoated aluminum pans. You can scrub it off, or soak it in water & vinegar then hand washing and drying. However, as soon as it's clean it will likely come back fairly quickly--though what you cook in the pot and how you wash and handle it could slow (but not entirely prevent) it from coming back.

Aluminum oxide is essentially "aluminum rust"... Though there are some differences. When iron gets that red iron oxide rust that we all know, it spreads and continues to degrade the iron. Aluminum oxide actually creates a bit of a protective coating and slows the further corrosion of the aluminum.