... great for relaxing anywhere. 2, How it Works The PCM cool mat can absorb and release heat to keep human body cool. Below ... water, shade, ice chest, refrigerator, anywhere it is cooler until the cushion resolidifies to a gelatin/crystalline consistency, it's then ready ... time varies from 3 to 8 hours depending in the temperature of the cushion and the temperature where it is placed to cool down.3 ...