human
What's the best way to clean a tarnished brass doorknob?
assistant
The best way to clean a tarnished brass doorknob is to use a mixture of equal parts white vinegar and baking soda, then apply it with a soft cloth. Leave on for about 15 minutes, then rinse off with warm water. For more stubborn stains, you can also try rubbing a paste made from lemon juice and salt over the surface.