Uniweld’s Cool Blue™ Heat Sink Paste protects the rubber and plastic seals in ball valves, solenoid valves, reversing valves and heat-sensitive materials. To prevent overheating, a heat transfer cool indicator has been added. As the paste absorbs heat, it changes to a dark blue. Safe to use, non-toxic, harmless to skin and odorless. Easy to clean: wipe with a cloth or wash with water.