When I saw her, I thought it was a joke or a mistake: why should we water a vase with ketchup?
I say a vase, but in fact any brass and copper object which has tarnished with time will be like a new one with ketchup!
Cover copper or brass with ketchup.
Wait 40 minutes.
Rinse with tap water.
Wipe with a soft cloth.
Without any rubbing, your copper/brass has a beautiful color!