sulfate (barite), calcium carbonate (chalk) or hematite . Various thickeners are used to influence the viscosity of the fluid, eg. Xanthan Gum, guar gum , glycol , carboxymethylcellulose , polyanionic cellulose (PAC), or starch . In turn, deflocculants are used to reduce viscosity of clay-based muds; anionic polyelectrolytes (eg. acrylates ,