Soil texture The number on the hydrometer that is visible (above the soil solution) is recorded. A blank (containing only water and the dispersing agent) is used to calibrate the hydrometer. The values recorded from the readings are used to calculate the percent clay, silt and sand. The blank is subtracted from each of the three readings. The calculations are as follows: Percent silt = ( dried mass of soil - (sand hydrometer reading - blank reading) / (dried mass of soil) *100 Percent clay = (clay hydrometer reading - blank reading) / (dried mass of soil) *100 Percent sand = 100
Wattle and daub driven into the ground with small branches (wattle) interwoven between them make the structural frame of the wall. Mud or an adobe clay (daub) is covered outside. To provide additional weather protection, the wall is usually plastered. Wattle and daub Wattle and daub is a composite building material used for making walls, in which a woven lattice of wooden strips called "wattle" is "daubed" with a sticky material usually made of some combination of wet soil, clay, sand, animal dung and straw. Wattle and daub has been used for at least 6,000 years and is still an important construction material