How to Clean Copper Mugs
To clean copper mugs, hand-wash them with a sponge and mild dish soap after each use. Rinse the mugs in cold water, then dry them thoroughly with a cotton cloth. To ensure there is no water that can tarnish the copper, dry the mugs a second time with a new cloth. If the mugs have already tarnished, dip a lemon wedge into a bowl of salt, then scrub the mugs with the lemon in a circular motion until all of the tarnish is removed. Rinse the mugs and dry them thoroughly after you have cleaned them.
Apply mild dish soap with a sponge. Then scrub the mugs with the sponge in a circular motion. Scrub the mugs until dirt, grime, and dust are completely gone. Rinse with water. You may use cold or warm water to rinse the mugs. Rinse until all the soap and residue are gone. Dry them off with a cotton cloth. Thoroughly hand-dry each mug with a cotton cloth. Pay attention to small corners and crevices when drying. Dry again. Use a new cloth to dry the mugs a second time. Drying the mugs a second time will ensure that all the water is gone. Make sure to remove all drops of water since any remaining water can cause oxidation and tarnish. Pour 4 tablespoons (59.1 grams) of salt onto a plate. You can use regular table salt, sea salt, or any other kind of plain salt. Depending on how many mugs you are cleaning, you may need more salt. Cut one lemon into fourths. Use a kitchen knife to cut the lemon into fourths. Alternatively, you can cut the lemon into halves. If you are cleaning multiple mugs, then you may need two or more lemons. Place the lemons onto the salt. Rub them into the salt. Make sure the fleshy part of the lemon is completely covered with salt. Scrub the mugs with the lemons. Do this using a circular motion. Scrub the outside and inside of the mugs until all the tarnish is removed and their surfaces shine again. Rinse them with water. Place the mugs under cold or warm running water. Rinse them thoroughly until all lemon, salt, and residue are removed. Use two cotton cloths to dry them. Take the first cloth and rub it over the mugs, making sure to dry all traces of water. Then take the second cloth and dry the mugs again. This will ensure a thorough dry. Add 3 parts baking soda to 1 part vinegar to form a paste. Make sure to add the baking soda to the vinegar. Then mix them together until a paste forms. You want the paste to have a toothpaste-like consistency. Apply the paste with a sponge. Cover the inside and outside of the mug with the paste. Let the paste set for five minutes. Depending on how tarnished your mugs are, you may need to let the paste set for longer, i.e., 5 or 10 minutes more. Scrub the mugs with a sponge. Do this after the paste has finished setting. Using a circular motion, scrub the mugs until all the tarnish is gone and their surfaces shine. Rinse with water. Rinse the mugs with cold or warm water. Rinse them until all traces of the paste and residue are gone. Double dry the mugs. Take a cotton cloth and wipe down the mugs once. Then go over the mugs again with a second cloth, making sure to dry all traces of water. This will prevent further oxidation and tarnish. Squeeze ketchup onto a plate. Use 1/3 cup (80 ml) of regular ketchup. Depending on how many mugs you are cleaning, you may need to use more ketchup. Dip a toothbrush into the ketchup. Spread a thin film of ketchup over the outside and inside of the mug. Let the ketchup set for 5 minutes. If your mugs are very tarnished, you may need to let the ketchup set for a longer amount of time like 10 to 15 minutes. Scrub the mugs with the toothbrush. Scrub the mugs in a circular motion with the toothbrush. Scrub until all the tarnish is gone and the mugs' surfaces shine again. Rinse with water. Run the mugs under cold or warm water until all the ketchup is removed. Dry thoroughly. To dry the mugs thoroughly, dry them twice. Use a clean cotton cloth to wipe the mugs down. Then wipe them down again with a second cotton cloth. Make sure all traces of water are gone before storing your mugs. 
Apply mild dish soap with a sponge. Rinse with water. Dry them off with a cotton cloth. Dry again. Pour 4 tablespoons (59.1 grams) of salt onto a plate. Cut one lemon into fourths. Place the lemons onto the salt. Scrub the mugs with the lemons. Rinse them with water. Use two cotton cloths to dry them. Add 3 parts baking soda to 1 part vinegar to form a paste. Apply the paste with a sponge. Let the paste set for five minutes. Scrub the mugs with a sponge. Rinse with water. Double dry the mugs. Squeeze ketchup onto a plate. Dip a toothbrush into the ketchup. Let the ketchup set for 5 minutes. Scrub the mugs with the toothbrush. Rinse with water. Dry thoroughly. 