How the Test Strips Work:
These economical test strips consist of paper saturated with cobalt chloride. The test strips show high relative humidity or the presents of water by changing from blue to pinkish-white. The humidity indicating strip show a more precise relative humidity. Cobalt chloride is a hydroscopic salt compound and exists in two forms. The anhydrous cobalt chloride salt is blue and the hydrated salt is pink. When the hydrated salt is gently heated, the blue anhydrous salt is reformed.