Aqualabo - Model 1KT001 -Hardness Test Kit for All Types of Water (3 Bottles) 1 Drop = 2°F

The dropper titration method changes the color of the sample from red to blue at the equivalence point. The number of drops needed for the color to change represents the hardness concentration. Total Hardness (TH) of water is expressed in French degrees (°f), where 1°F corresponds to 10 mg of CaCO3/L