Measure the centipoise, or cP, of a fluid using a viscometer. Centipoise is a unit of viscosity in the centimeter gram second system; in the International System of Units the pascal second replaces centipoise.
- Set up the viscometer
A simple viscometer is a u-shaped glass tube with a bulb near the top of one arm of the bend and a second bulb near the bottom of the other arm. Use a test tube clamp to hold the viscometer in place vertically, keeping the instrument straight. Make sure the temperature is even across both sides of the viscometer.
- Measure the test fluid
Use suction to draw the test fluid into the uppermost bulb; note the markings that appear above and below the bulb. Release the suction, and the fluid moves from the upper bulb into the lower one. The amount of time that passes while the fluid level moves between the markings is important in calculating viscosity.
- Calculate the viscosity
Viscometers all have a factor, either on the instrument itself or in the accompanying manual. Multiply the flow time of the fluid by the viscometer factor to obtain the viscosity. If you need to convert between measurement systems, 1 cP is equal to 1 millipascal second, or mPa*s.