Sterling silver is a durable and valuable material. It is used to make a plethora of objects, including eating utensils, jewelry, serving trays, vases and coins. If you own a sterling silver mug and it has been painted, or perhaps has a paint spill on it, it should come off without damaging the silver. Note that it might not be paint on the mug but varnish, in which case you should try cleaning the mug with a silver cleaner or polish first.
Soak the silver mug in hot, soapy water for three or four hours. To keep the water hot, heat water on the stove to approximately 200 degrees F, using a candy thermometer if necessary. You can also place the mug in a crock pot set on low.
Wipe the loose paint off with a rag after soaking it in hot water. For stubborn areas, scrub the paint off the silver mug with a soft toothbrush or scrub it gently with a nylon bristle brush. If this method is ineffective or some paint is left over, soak the mug again in hot, soapy water or proceed to the next step.
Remove the paint with a solvent that removes paint, such as fingernail polish remover or denatured alcohol. Soak a cotton ball or rag with the solvent and rub it on the bottom of the mug to verify it will not damage the surface and that it's effective in removing the paint. If it works well, remove the paint from the rest of the mug in a similar manner. If not, try a different solvent.
Clean the silver mug thoroughly using hot, soapy water after the paint is removed. Dry it with a soft rag; otherwise, it is likely to develop water spots.