I've been boiling water with some new pots on a gas stove and it leaves (left) a stain on the bottom (on the inside) that has the same color pattern as when oil drifts on water.

What could be causing this and is it 'a bad thing' ?

  • Does it look like this?
    – Aaronut
    Commented Mar 12, 2011 at 15:59
  • @Aaronut: No that's not what it looks like, it's really got purple/blue/... colors like an oil stain. I would upload a picture but i won't be home until tomorrow.
    – Aerus
    Commented Mar 12, 2011 at 16:25

1 Answer 1


I've seen a number of varying explanations of this phenomenon, but all agree that it's a normal effect to see on stainless steel cookware and is harmless (assuming you are cleaning your pan well).

It is probably some combination of the minerals in your water, high heat, and oil or soap residue. The harsher detergents and sometimes less effective rinse of a dishwasher might make the problem more prevalent than if you wash the pots by hand. It may also be caused by oxidation of the metal itself and you can remove it by scouring or with a bit of vinegar or lemon juice.

You can pretty much ignore it, unless it bothers you for aesthetic reasons.

  • Thank you, i just wanted to know if i was doing something wrong and if it could have any bad side-effects. This pretty much wraps it up :)
    – Aerus
    Commented Mar 12, 2011 at 16:27
  • This is something people commonly do to titanium to get a nice permanent rainbow-into-indigo effect without paint.
    – bikeboy389
    Commented Mar 13, 2011 at 0:04
  • As a side note: this tends to occur where you have used too large a burner for the pan or had the gas turned up too high. Flames should be under the pot/pan and not lick up around the sides. Although it isn't dangerous it could indicate you're wasting energy and if your pan has a handle doing this will reduce the lifespan of the pan.
    – vwiggins
    Commented Mar 14, 2011 at 13:34

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