I believe this question is at the confluence of cooking, chemistry, and biology. We steamed some lobster tails last night. Put them in an anodized aluminum pot on a stainless steel steamer basket over some boiling water. This morning, it took me over 45 minutes to clean the basket and the pot. Whatever cooking residue that remained on both pieces was approximately impossible to remove. I figure that the heat somehow released some sort of chitinous cement from the shells that deposited itself on the metal. Maybe someone here can illuminate me on why it was so damned hard to clean up after that meal.
If the water was hard, that is, containing soluble salts of magnesium and calcium, boiling forms an insoluble double salt, calcium magnesium carbonate. This is not soluble in hot or cold water.
Waiting until the next morning to clean the dishes surely did not help. Unless they were soaking in hot soapy water all night long. To prevent it, next time wash the pots right after dinner. Or thoroughly soak them first.
I bet that was caused by the “Lasagna Battery” effect.
Similar thing happens if you store lasagna in a steel pan, then cover it with aluminum foil. It forms a shorted battery, with the two metals forming the two battery plates. Holes are eaten into the foil. If you put wax paper on the edge of the steel, so the foil never touches the steel directly, then the circuit is broken and the foil won’t corrode.
Once the lobsters started cooking, the water no doubt turned salty. Any dissolved material can be “electroplated” onto the metals. Or more probably, the aluminum would start corroding rapidly into alumium oxide, and become covered with big white patches of “rust.” If you could scrape it off, you’d find corroded bare metal underneath.
Now that’s what I’m talkin’ about! Of course I scrubbed it a bit before I let the pot soak over night in soapy water. And of course I’ve cleaned pots and dishes before. But I’ve never encountered such a persistently difficult residue before. I think it’s possible that I’ve had an encounter with the Lasagna battery effect. Wonderful resource, this site.
xo, C.