Cotton is a hydroscopic material. It is generally known that the fiber moisture content in equilibrium is a function of the moisture in the surrounding atmosphere. Furthermore, both the fiber length and strength change with any change in the absorbed moisture content of the fiber. In order to be able to compare results from different laboratories, ASTM standard procedures require that all fiber testing be done at standard conditions (21 +/- 1°C and 65 +/-2% relative humidity).

A new fiber moisture measurement technique has been developed that measures the fiber moisture at the break position in the HVI while the cotton fibers are measured for length and strength. This development is significant in that the moisture content of the actual cotton fibers under test are measured directly. In addition, the moisture measurement is made at the same time as the length and strength tests are completed, thus reducing potential decoupling in the measurements. With this improved method for determining fiber moisture content, corrections can be made in the fiber length and strength such that the requirements on the laboratory conditions (temperature and relative humidity) can be relaxed.