Medals involve not only the metal itself but also the ribbon, and these materials are susceptible to damage from moisture, dust, sunlight, and changes in temperature. Museums keep medals in locations with regulated temperature, humidity, and light levels to minimize discoloration and deterioration. At home, collectors should keep medals clean and dry, and should store them in a location that is not prone to extreme temperatures. Damp conditions corrode the metals and rot the ribbons, while high temperatures make ribbons go brittle. Acid-free cardboard boxes are a good storage solution, but wooden boxes coated with polyurethane resin are also acceptable. Collectors should avoid polishing medals, as the polish causes abrasion, and they should always wear gloves when handling the medals.