Clay and glaze suspensions have normally densities between 1.0 and 2.0. On hydrometers used for measuring glaze and slip densities the densities between 1.0 and 2.0 have been divided into 200 units. These units are called degrees Twaddell and the formula for calculating these is:
ºTW = (density - 1) x 200
Density = ºTW/200 + 1