I have read countless articles and posts about alumninum pots and pans becoming black after only boiling some water in them. Most writing focus on ways to clean them. However, I am only interested in knowing WHY do they turn black.

We are not talking about greasy food over-cooking. You only put water in the pot, and after boiling the water the water and/or the pot turns black !!!!!!

It maybe hard water or whatever but I need toi understand this, preferrably in chemical terms. Is the black material dangerous or toxic ?? Are there other aluminum pots that do not turn black ??? etc.

The issue is important for preppring cookware for a BOB. Aluminum is lighter and cheaper , but stainless steel is worry-free in this regard.

Thanks