A Viscosity Test to Characterize Emulsions

There are various ways to measure viscosity and you can always get creative as long as you can find a way to correlate your method with the stickiness of the emulsion. Here we used an acrylic pipette stand for a slanted surface; however any flat, smooth surface at an angle could work. In addition to the slope method, viscosity can be measured by a falling ball viscometer, viscosity cup, capillary viscometer, and so forth. 

1. Using a pipette, take up a bit of the sample. 
2. While tilting the pipette stand/clear surface so the incline part becomes parallel to the floor, drop appx. 2-3 droplets of the sample on top of one of the four purple dots (make sure the sample fits the dot).  
3. Angle the surface to begin the experiment while simultaneously starting the timer for 30 seconds, and mark/record how far each sample goes at the end of the 30 seconds. 
4. Take the multiplicative inverse (1/distance) of the distance traveled by the sample to approximate viscosity. 
5. Record the viscosity category according to the standards below (in units of cm-1). 
   • <0.2 : Low Viscosity
   • 0.2-.0.5: Medium Viscosity
   • >0.5: High Viscosity
6. Compare viscosity values with other groups and your lotion. What can you hypothesize about the relationship between viscosity and emulsion state?