Ketchup cleans copper and brass.

Macie w domu stary ketchup? Nie warto go wyrzucać, bo pięknie czyści mosiądz i miedź. 
 Sprawdziłam i potwierdzam!                       
From the knocker on your front door to the extra-special necklace you brought home from the craft market, brass and copper goods are showing up everywhere. Over time, these shiny treasures will start to tarnish, and we heard that ketchup can help get them back in shape. But does it really work? we gave it a try...
Read more:
http://www.apartmenttherapy.com/how-to-clean-copper-and-brass-with-ketchup-223741

or watch : https://www.youtube.com/watch?v=zVzaargKfCE