Water Vapour Transmission Rate Tester (Astm E- 96)

WATER VAPOUR TRANSMISSION RATE TESTER (ASTM E- 96)In the Desiccant Method the test specimen is sealed to the open mouth of a test dish containing a desiccant and the assembly placed in a controlled atmosphere. Periodic weighing determine the rate of water vapor movement through the specimen into the desiccant. In the Water Method, the dish contains distilled, water, and the weighings determine the rate of vapor movement through the specimen from the water to the ,controlled atmosphere. The vapor pressure difference is nominally the, same in both methods except in the variation, with extremes of humidity on opposite sides.Where:In inch-pound units:G = weight change, grains (from the straight line),t = time during which G occurred, h,G It = slope of the straight line, grains/h,A == test area (cup mouth area), fif, andWVT = rate of water vapor transmission, grains/h· ft2.In metric units:G = weight change (from the straight line), g,T = time, h,G It = slope of the straight line, g/h,A = test area (cup mouth area), m2, and WVT = rate of water vapor transmission, g/h· m2.