Bit Balling Bit balling usually occur while drilling shale. Clay adhesion is a function of the electrochemical attraction of clay to clay solids and clay to metal (surface tension). The reaction begins when clay solids become wet, and hydration/dispersion of the clay occurs. Adhesion magnitude is determined by the degree of clay hydration, the chemical properties of the clay, the chemical composition of the mud’s aqueous phase, and the proximity between reactive solids or the solids concentratio