It is a special type high molecular weight polymer and is used in very small quantity to increase the viscosity of API Bentonite suspension of very low concentration of bentonite in the system.

With its two-fold yield is able to maintain a given viscosity with one-half the normal clay solids. This is an excellent additive for low solid drilling fluids. It also tends to cause drilled solids to form agglomerates and settle out. This further enhances its use as an additive in weighted and unweighted non-dispersed drilling fluid systems.
COMMON NAME - BENTONITE EXTENDER (API)