VISCOSITY FORUM: Ask the experts

How do you test construction materials for

Measuring Viscosity? Kinematic or Dynamic Method. How to Choose?

11/21/13 at 11am EST

An Interview With Pat Maggi

Capillary and rotational viscometers are used around the world to measure viscosity. Why are there two different methods? Does each have certain advantages that recommend its use for certain categories of materials? This interview will review various test methods that encompass one or the other technique and provide guidance on how best to proceed when in doubt on the choice. read more

How do you test construction materials for

How do you test construction materials for "flowability"?

11/6/13 at 11am EST

Dr. Guy Rosenthal Interview

How do you test construction materials for "flowability"? For example, when you open a tub of joint compound, does it have the right consistency? Do you know right away when you stick your trowel in? Or is the proof of the pudding in how it spreads? read more

Life Below the Yield

Viscometer vs. Texture Analyzer


An Interview with Ross Clark

When does a viscometer make sense and when does a texture analyzer make sense? read more




Customer Challenge: My Company just discovered that our viscometer with RV torque is out of calibration. We checked it with a 5000 CPS viscosity standard (rated 4750 cP @ 25°C) using the 27 spindle in Small Sample Adapter at 20 rpm. Our measured viscosity reading is 5475 cP. We are out of calibration by 450 cP. Can we correct our QC viscosity data since the last time we performed a cal check? Do we lower the measured values by 450 cP? Do we need to have our viscometer serviced?


No, you should not adjust your QC viscosity data. You don’t know exactly when the viscometer went out of calibration. You may want to consider running a cal check more frequently. If you notice that the QC tests on your material are trending higher, you should run a cal check on the viscometer to find out whether your product is changing or the instrument is reading incorrectly.

Return your viscometer to the nearest authorizedBrookfieldServiceCenter. You can usually get a loan instrument if needed while your viscometer is being serviced. The turnaround time is only a few days and the cost is small compared to the problems that might be caused by shipping product that is out of specification. You will also receive a new Certificate of Calibration for your viscometer.


CUSTOMER CHALLENGE: What is the recommended procedure for performing a calibration check on your viscometer to verify that it is reading correctly? How often should you perform a calibration check?


Obtain a viscosity standard fluid which has a known viscosity value at a specified temperature. For example, Brookfield viscosity standard fluids are normally calibrated at 25°C.

Choose the spindle that you want to use to make the calibration check. Select 3 rotational speeds. Test the viscosity standard at each speed and record the measured viscosity value.

To find out if your test is successful, enter the information from your test into the calibration spreadsheet at
/calibration.asp. This spreadsheet will automatically tell you if the measured viscosity values are within the 1% tolerance that is authorized.

If the test fails, repeat the test again to make sure that it was done correctly. If it fails a second time, contact Brookfield to arrange for a calibration service.

Frequency of the calibration check depends on how often your viscometer is used. In busy QC labs, it may be customary to perform a weekly test. Performing a check at least monthly is recommended. It is also necessary the calibration check whenever there is concern that the instrument is not reading correctly.


CUSTOMER CHALLENGE: We're developing a thick shampoo that has particles in it. We are using a T-bar spindle to measure viscosity, but we don't feel our readings have been very accurate. For example, we can test one formulation that doesn't seem to flow when tipping the beaker and it will be 20,000 cP but another formulation seems to flow as soon as you move the container slightly will read 60,000 cP. Do you think that the viscosity measurements are correct? Is there a different test that could help us understand the viscosity behavior? The critical marketing issue is how fast the product will flow out of the bottle when opening the cap. Do you have any suggestions on how to test this type of flow behavior?


The important issue that you want to understand is how quickly the shampoo transitions from "non-flowing" to "pourable". You want the customer to admire the thick appearance in the bottle, but when used, you want the shampoo to come out easily so that it can be used.

There is a test method called "Thix Index" that measures viscosity at 2 different speeds that are an order of magnitude apart. In this case, you might try 1 rpm and 10 rpm or maybe 5 rpm and 50 rpm. Divide the viscosity reading at the low speed by the viscosity reading at the high speed. This ratio is called "Thix Index". If the value of the ratio is close to 1, then there is little change in the viscosity and it will not pour easily. If the value of the ratio is close to 10, then the shampoo thins out very easily and may flow out of the bottle too quickly. Values around 3 or 4 may be closer to what you are looking for.

Brookfield's Rheocalc T software has the Thix Index test as one of the standard methods that can be selected. You can also program the test directly in the DV3T Rheometer or DV2T Viscometer.

The choice of spindle is another issue to address. The T-bar is not the ideal spindle for measuring a shampoo with particles. Depending on particle size (average diameter of the particle), consider the vane spindle, which traps the particles in the space between the vanes and shears the mixture against similar material outside the circumference around the vane. If the particles are small, you might be able to use the Small Sample Adapter as an alternative.


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View the viscosity of water at temperatures between 0 - 100° C.

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Instant view of some dynamic viscosities of Newtonian fluids.

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The cup to viscosity conversion engine assumes fluid is Newtonian.

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Examples of values for typical food and personal care products

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