Abrasion
 Adhesion
 Application
 Color/Gloss
 Density
 Dispersion
 Drum Handling
 Drying Time/Gelation
 Film Flaws
 Film Thickness
 Hardness
 Impact & Flexibility
 Lab Apparatus
 Measuring Instruments
 Moisture/Air/Temp.
 Optical Instruments
 pH & Conductivity
 Publications
 Surface Profile
 Surface Tension
 Viscosity
Home  >>  Products  >>  Viscosity  >>  Measuring Viscosity in a Zahn Cup

Measuring Viscosity with a Zahn Dip Cup: The Proper Process


 

Viscosity is an important property to measure when it comes to many industries, such as food, cosmetics, paint, pharma and many more. Zahn cup viscometers are a common tool used to determine the viscosity of a wide variety of viscous materials.

It can be a tricky process, but this article will outline the proper procedure for using a Zahn Dip cup. First, make sure that you have selected the correct size viscosity cup for the material you are measuring. Next, thoroughly clean both the cup and your sample container with the proper solvent. With these simple steps below, you can measure accurate viscosity every time!

  1. Examine the cup for obvious obstruction or damage to the orifice area and general cleanliness of cup.
  2. Pour enough of your sample into a 500 ml container to totally submerge the cup.
  3. Using a calibrated ASTM thermometer bring your sample material to a target temperature (usually 25.0°C ± .5°C). Proper temperature is very important. By wrapping a hand around the beaker and slowly stirring your material, the temperature can be slightly raised.
  4. Place cup in the material and allow 1 to 5 minutes for cup and liquid to reach thermal equilibrium.
  5. Raise the cup vertically to no more than 6” from the surface of the liquid. Start timing with a stopwatch with accuracy of one tenth second or better as the top edge of the cup breaks the
    surface of the liquid.
  6. Leave the thermometer in the beaker to ensure the temperature remains constant throughout the run.
  7. Stop the timer when the first definite break in the efflux stream occurs near the bottom of the cup. Be sure to keep air bubbles at a minimum; they will sometimes cause an apparent break prematurely.
  8. Record time and temperature and repeat. Keep temperature drift between runs at ±.2°C. Disregard any runs that are more than .5 seconds apart.

 

Selecting the Correct Size
The first step in using Zahn cups is to select the correct size. These viscosity cups come in a variety of sizes, each with its benefits. The size of the cup you use is important for accuracy. If you use a cup that is too small, you will not be able to measure the sample accurately. Conversely, if you use a cup that is too large, you may overestimate the viscosity of the sample. Make sure to select the appropriate size for your application to ensure accurate results. You can use the Insta Visc Viscosity Calculator app to determine which viscosity cup would be best for your specific viscosity range.

 

Thoroughly Clean the Cup and Sample
Once you have selected the correct Zahn size cup, it is important to clean both the cup and your sample. Any dirt or debris on either can lead to inaccurate viscosity measurements.

It is important to use the correct solvent when cleaning the cup and sample. Different solvents can be used to clean different types of materials. For example, an organic solvent can be used to clean a plastic cup, while a water-based solvent can be used to clean a metal cup. The same is true for the sample. A water-based solvent can be used to clean a non-polar sample, while an organic solvent can be used to clean a polar sample.

To clean the cup, first, rinse it with warm water to remove any residual solvents or debris. Next, use a solvent such as a methyl ethyl ketone (MEK) to clean the inside of the cup. Be sure to rinse the cup again with warm water to remove any remaining solvent.

To clean the sample, use a solvent such as MEK to remove any dirt or debris. Be sure to rinse the sample with warm water to remove any remaining solvent.

 

Observe and Report the Flow Rate
The viscosity of a material is directly related to how long it takes for the liquid to flow out of the cup. By timing how long it takes for the sample to empty, you can accurately calculate the viscosity of your material.

 

There are a few things to keep in mind when performing this measurement:

  • Raise the cup vertically to no more than 6” from the surface of the liquid
  • The stopwatch should be started as soon as the top edge of the cup breaks the
    surface of the liquid
  • The stopwatch should be stopped when the first definitive break in the efflux stream occurs near the bottom of the cup

Once you have recorded the flow time, you can use the Insta Visc Viscosity Calculator app to find the viscosity value of your material. The flow time will be directly correlated to the viscosity of the liquid; the longer it takes for the liquid to flow, the higher its viscosity will be. By using a viscosity chart, you can determine the viscosity of your material with a high degree of accuracy.

Summary
Zahn cup viscometers are a reliable, economical, and easy-to-use way to measure the viscosity of a material. By following the proper procedure and using a viscosity chart or the Insta Visc Viscosity Calculator app, you can obtain accurate results that will be helpful in your viscosity measurement efforts.

Also, visit our 30 Seconds in a Zahn Cup article and the Viscosity Cup FAQs for additional information.






top

Call HAVE QUESTIONS?
    954.946.9454
Email PREFER TO EMAIL?
    gardner@gardco.com
  FIND PRODUCTS LEARN MORE ORDERING INFO ABOUT US
  By Category Email Registry How to Order Contact Info
  By Industry Trade Shows Request Quote History
  New Products Test Lab Info Order Form FAQ's
  Sales/Trade-In Offers Articles/Links Repairs/Service Policies




  © 2020 Paul N. Gardner, a BYK Instruments Company | Contact | Policies Facebook  YouTube  Blogger