... change color or put a lighted cigarette butt on the quartz stone,then it shall not change color. ♦Resistance to soiling ... :drop the soy sauce,vinegar,coffee on the quartz,clean it with the cleaning agent 24 hours later,it ... than 0.04%,sprinkle few drops of water on the quartz stone ,it shall not be whitish after 24 hours. ♦ ... ,±1.5 for 20 plate. ♦Material:more than 93% natural quartz sand