For syrup compare the average viscosity measured by the Zahn

For syrup, compare the average viscosity measured by the Zahn cup with the average viscosity measure by the rotational viscometer. Calculate the percentage difference from the total average. Which method do you believe produces better results? Explain.

Method

Average Viscosity

% difference

Brookfield Rotational Viscometer

5400

13.46683196

Zahn Cup

4118.2

13.46683196

Total Average

4759.1

n/a

Solution

Zahn cups are simple to use and inexpensive. They are cups designed with a hole in the bottom and are intended to be dipped into the liquid that is to be measured. A stopwatch is used to time how long it takes to empty the contents of the cup by draining the liquid through the hole. The results are measured in, “Zahn Seconds.” Only low viscosity material is suited to measurement by use of a Zahn cup, generally no higher than 1500 cps. It is important to recognize that Zahn cups measure viscosity under conditions of no shear. Shear (force) affects the apparent viscosity of all water borne emulsions. All methods of applying glue exert shear force on the glue, causing the viscosity to be altered while it is under shear. This can lead to confusing results.

Brookfield Engineering manufactures viscometers that have become the standard tool for measuring viscosity. The instrument can measure viscosity under various levels of shear and report the result in centipoise. Quality assurance testing is performed at a specified set of conditions, such as defining the spindle, the rotational speed and the temperature of the test conditions. Brookfield viscometers produce values that are more relevant to understanding how an adhesive is likely to behave on application equipment.