Things You'll Need
Baking soda is used for many things, including cleaning costume jewelry. Due to its mild abrasiveness, it removes stuck-on particles and will polish most hard substances, including coins. You can clean most coins using baking soda and water alone; however, you should note that cleaning old coins may decrease their value. If you suspect a coin may be valuable, consult with a professional coin dealer before attempting to clean it.
Lay a clean towel next to your kitchen or bathroom sink.
Pour baking soda in a small bowl. You’ll need about ¼ tsp. per coin.
Put a stopper in your sink drain, if available. If you don’t have a stopper, place a heavy cloth over the drain in case you lose your grip on one of the coins.
Wet a soft-bristled toothbrush under your sink faucet. Dab the bristles in the bowl of baking soda and, holding a coin in your hand, begin gently scrubbing the coin. Use a gentle, light touch when scrubbing. Tarnish should immediately start coming off, especially if the coins are silver.
Rinse the coin beneath warm running water and then dry it with a soft cloth. Place it on the towel next to the sink. Repeat this process with all the coins you choose to clean.
The use of baking soda will polish the coin but it will also leave minute scratches on it that are noticeable under magnification.