Kyushu Circle Diatomite Coaster Material: Diatomite Size: 10cm Colors: - Dark Gray - Light Gray - Sky Blue Shape: - Circle DISCLAIMER: DUE TO ITS HIGHLY ABOSRBENT PROPERTIES, OUR KYUSHU DIATOMITE COASTERS MAY HAVE THE CHANCE TO ABSORB STAINS FROM COFFEE OR COLORED DRINKS. NONETHELESS IT IS STILL EFFECTIVE AS IT IS.  CARE INSTRUCTIONS: New diatomite products usually have micronized powder which is natural and not a quality problem. You may use a slightly damp cloth to gently rub it away. For stains (coffee or other colored drinks), wash it with water and gently grind the surface using sandpaper until stains are not visible anymore. Leave in a dry area and let it air dry. To avoid damages, such as craking or curling problems, store the diatomite coasters in a well-ventilated area. Direct sunlight exposure for a long time is highly discouraged.  Absorption ability of the diatomite coaster may be affected with humidity and temparature. After long-time use, you may rub it with sandpaper to keep it highly absorbent .