Painting the Lab

One possible worry during rotational tests is that the sample can be expelled from a cone or parallel plate fixture at high shear rates.  This occurs when the centrifugal force exceeds the surface tension.

My most memorable experience occurred in my sales days.  I was installing a special system with a 6" (152.4 mm) fixture.  To test it out, I bought a bottle of corn syrup, because I wanted to use something more viscous than water.  There was not enough syrup for the fixture, so I added water to the fixture.  It turns out that water mixes slowly with the corn syrup that's available in American supermarkets.

I started the fixture using controlled stress mode, which was my first mistake.  As the water and corn syrup mixed together, the viscosity started to drop.  As the viscosity dropped, the fixture started to speed up and began fling the sample around the lab.  I shut down the system before all the sample made it to the laboratory walls.

A former colleague of mine referred to this phenomenon as "earning your stripe."

Updated 4/26: (Hey, I have an idea for a new t-shirt!)