Sep 28, 2017 · To keep their luster intact, polish garnet stones by hand regularly. Rub the garnet stones with the clean cloth to remove any dust. Use soft, lint-free microfiber cloths to protect the gemstones. Mix a small amount of mild liquid hand soap with lukewarm water. Stir the soap and water with the baby toothbrush.. Simply dip your jewelry in a mixture of warm water and liquid soap, preferably one which is colorless and odorless. Soap for woolens, castile soap, or even a hand soap (make sure it is free of antiseptic and harsh chemicals) is good enough for the job. Thus, if you're wondering how to clean jewelry with dish soap, this is the way to do it.