To make a homemade copper polish, make a paste out of salt, flour and white vinegar. Rub the paste onto the copper with a cloth until it appears shiny, rinse, then let it dry. To clean tarnished copper, scrub it with a salt-covered lemon.
Make an all-natural homemade copper polish by combining 1/4 cup all-purpose flour and 1/4 cup fine sea salt in a small mixing bowl. Stir while slowly adding white vinegar to make a thick paste. Using a soft rag or sock, rub the paste on the copper until it is shiny, then rinse and let the copper piece dry.
Alternatively, mix a small amount of cream of tartar or baking soda with lemon juice. Apply the mixture to the copper with a soft cloth, and let it sit for at least five minutes. Wash with warm water, then rub the copper dry with a soft cloth.
For tarnished copper, cut a lemon in half, and dip it cut-side down in a small bowl of kosher salt for copper cookware, or table salt for delicate copper. Scrub the copper with the lemon to remove the tarnish, then rinse thoroughly with warm water. Dry with a soft cloth, then polish with a second cloth using circular motions until it appears shiny.