Water Activity (Aw) is the water vapor pressure generated by the free water in the mud. The mathematic formula is Aw= (vapor pressure of the water in the mud at °C)/(vapor pressure of pure water at °C). It is used to determine the mud quality when the salts in an oil based mud are too complicated to analysis (usually in field work). Electrohygrometer is employed to measure the Aw value.
You may also be interested in: