What is the best homemade ring cleaner?

Plain dish soap works because it is a surfactant: a molecule with one end that bonds to water and one end that bonds to oil. Skin oils, hand cream, sunscreen and cooking residues are all oil-based, and water alone cannot dissolve them. Surfactants surround each oil molecule, lift it off the metal or stone and suspend it in the water so it rinses away. Dish soap formulations are tuned for exactly this job, which makes them the closest household match to the surfactant blends used in professional jewellery cleaning solutions. Brand does not matter much. Stick to plain dish soap rather than the heavily perfumed varieties, which can leave a residue of their own.

Three popular myths keep getting recommended online, and all three damage rings. Toothpaste is the worst offender: it sits around 3 on the Mohs hardness scale, harder than gold (2.5 to 2.9) and silver (2.7), so it scratches the band finish even though the diamond is unaffected. Baking soda is mildly abrasive in the same way and slowly etches the alloy boundaries in gold. White vinegar is acidic enough to attack the metal alloys and the glue used in some settings, particularly opal doublets and emerald oilings. None of these are catastrophic in a single use, but the accumulated damage shows up as a dulled band finish that needs professional polishing to fix.