Table 2: API Standard Numerical Value Requirement for Drilling Grade Bentonite [²⁴]

RHEOLOGICAL PROPERTIES
Ɵ600 RPM	30 Minimum
Ɵ300 RPM	23 Minimum
PLASTIC VISCOSITY	6-8 Minimum
APPARENT VISCOSITY	12-15 Minimum
YIELD POINT	3*PV or 50 Maximum
YIELD POINT/PLASTIC VISCOSITY	3 Maximum