Fann Laboratory Mixers are two speed mixers, available in both 115 and 230 volt models. No load test speeds of 11,000 and 15,000 rpm. Supplied with the standard impeller blade for mixing either water-base or oil-based drilling fluids. PowerstatTM variable transformers (sold separately) provides an extended mixing speed range. Shearing devices vary widely in the amount of shear they impart. Longer shearing times may be required for low shear devices to achieve complete dissolution / hydration of fluid components; high shear devices may produce nearly completely yielded drilling fluid blends in a few minutes. Aging of drilling fluid samples tends to minimize differences in properties which can result from shearing treatment.