APPLICATION: Bentonite Clay is a rheological “thickening” additive for many products, such as paints.
* While a particular model/version may be used as an example in this method, any current or past model/version from the same series may also be used. Please consult a sales associate to discuss the most current instrumentation and software available.
The 10% by weight concentration of clay was created with distilled water and tested. The mixture was tested within a 600-mL, low form, Griffin beaker, at room temperature, about 23 °C. A Helipath stand was used with the small T-F spindle because of the high viscosity and "pasty" nature of the sample. The Helipath tests "fresh" material as it drills deeper into the sample. This may be a big advantage when testing materials whose structure breaks down and takes significant time to rebuild.
Our Rheocalc v3.1 software controlled the Brookfield LVDV-II+Pro. Data from this test is shown in Figure 1, below:
Figure 1: Viscosity as a Function of Time.
The spindle "drills" down into the sample from° to 156 seconds. There is a noticeable decrease in viscosity after 156 seconds, when the spindle works its way back up through previously tested clay. One noticeable aspect of the graph is that it shows the stratification of the clay mixture. From 25 to 50 seconds the viscosity remains fairly constant, and then it gradually increases as the spindle descends.
Acknowledgement: We wish to thank Southern Clay Products for generously providing us with a sample.