Polystone or polyresin chess sets are generally strong but can be brittle. Polystone can be easily shaped and is often painted. Therefore polystone is often the material of choice for colorful themed chess sets. The amount of detail of the figure and the painting is often reflected in the price of the chess set.
Polystone is a family of materials and is on the market under different names. Polystone consists of a filler material, like marble powder or quartz and a resin like acrylate or polyester. The material is poured into a mold and afterwards polished often painted. In general polystone is very strong and water resistant, however the variety in different materials is large. So always handle polystone with care to avoid surprises.
Polystone stays beautiful when handled with care, and it is best to prevent it from becoming dirty. Coffee, wine and vinegar can permanently stain unpainted polystone and should be removed immediately. Do not use dusters, particularly coloured ones, as they tend to rub the dust into the surface and may smear greasy dirt. In general the patina build up over time is not removed. Protection with a wax or oil is not adviced, since it is difficult to predict if the minerals will react with the wax or oil over time. These reactions can cause stains or discoloration which cannot be removed easily anymore.
Dry cleaning is preferred. Use a clean soft-bristled brush such as a makeup brush to avoid scratches. For difficult to remove stains a Q-tip dampened (not saturated) with acetone can be used.
Wet cleaning should always be tested to see if it has no adverse effect. Remove dust before cleaning, because otherwise the dirt will be absorbed. Spray the piece or chess board liberally with water before applying the cleaner with a sprayer. Polystone sometimes can absorb the cleaner. By wetting it beforehand, the cleaner will stay on the surface of the polystone and minimize penetration of the cleaner into the polystone. This action minimizes potential adverse effects by the cleaner, such as salt crystallization in the pores of the polystone. It makes it easier to rinse the cleaner from the polystone surface.
Clean with mild liquid dishwashing detergent (pH neutral) and warm water. Avoid cleaners that contain lemon, vinegar, or other acids; as well as scouring powders or creams. These often contain abrasives that can dull or etch calcareous polystones. Use white spirit only when needed for removing waxes and oily dirt.