Maybe this helps. I found also that chlorine tarnishes stainless, so I guess tap water is not good.
Polishing Stainless Steel with Glass Cleaner
If you have a stainless steel object that you are not using in the kitchen, then glass cleaner with ammonia works brilliantly for polishing and cleaning it. This method makes easy work of removing old water spots and built-up grime that has accumulated on your stainless steel. However, once the cleaning is finished, be sure to rinse the object with warm water and dry it thoroughly to remove any chemicals left behind by the glass cleaner.
Polishing Stainless Steel with Vinegar
If you need to polish stainless steel items used in the kitchen, then vinegar can effectively get the job done. White and cider vinegar work equally as well, so whatever you have in your cabinet will do. Just moisten a clean cloth with the vinegar and start cleaning your stainless steel cutlery or other items. This same technique can also be performed using a mixture of olive
oil and club soda.
Polishing Stainless Steel with Baking Soda
In a clean bowl, mix baking soda with some warm water until you make a paste. Use a clean cloth to rub the paste all over the stainless steel item and then rinse it with warm water and dry it with a clean cloth. The benefit of using this method is that it does not leave behind an odor, as using vinegar can sometimes do.
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http://www.doityourself.com/stry/kee...#ixzz0dM7Zw6X1