Rub the enamel with a lint-free microfiber cloth using a circular motion. If the enamel has a layer of dust or dirt on the surface, moisten the cloth before rubbing the enamel.
Add a drop of mild soap to the damp microfiber cloth, if the enamel is especially dirty. Rub the soapy cloth over the surface in a circular motion, then fold the cloth over and wipe away the soap. Dry the enamel with a microfiber cloth.
Treat tarnished areas of copper with a solution of one part lemon juice and one part water. Spot apply the solution to the copper with a cotton swab, avoiding enameled areas. Wipe the solution away as you go with a paper towel.
Rinse the copper, including the enameled areas, with cool water, if you've used lemon juice. Rub the enamel with a microfiber cloth as you rinse to remove traces of lemon acid from the surface. Dry the piece immediately with a microfiber cloth.