Careful....knowing the metal makeup and maintaining favorable patina of the button is important prior to cleaning it. Copper reacts badly to caustics and acidic compounds, steer clear of it. precious metals such as silver and do better with lemon juice, even C.L.E.A.R., lime scale remover, (picked that one up from Hoover Boys on YouTube and it does well on silver). Recently learned of a mild technique for copper and brass which I'm using, soap water a soft toothbrush, picking grit with toothpick or graphite pencil, then onto toothbrush again with vegetable oil to pull grit, grime and get definition. Here's a before and after of a brass breastplate I recently found and a copper large cent using this technique. Best advice I can give is experiment first on less valuable items but know your metals and what's recommended for cleaning each type and devices such as toothpicks, pencils and brushes. Good luck.