Moisture is known to affect the flowing properties of powders. However, the quantification and the understanding of the observed effects are far to be obvious.
It is well known in industrial applications involving powders and granular materials that the relative
air humidity and the presence of electrostatic charges influence drastically the material flowing properties. The
relative air humidity induces the formation of capillary bridges and modify the grain surface conductivity.
The presence of capillary bridges produces cohesive forces.