VISCOSITY MEASURING PROCEDURES
Data history
We recommend documenting the following information each time you take a viscosity measurement:
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Model or type of viscometer
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Spindle (and accessory)
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Rotation speed
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Sample container
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Sample temperature
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Sample preparation procedure (if existent)
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Spindle protection use
The process is necessary in the event of comparison of results with other organizations, in the interest of
being able to guarantee the possibility of reproduction of the results obtained.
The spindle and its protection
Examine each spindle before using it. If it’s damaged or eroded in such a way that its dimensions are
changed, it will provide false results for your viscosity reading.
The spindle protector (provided with every Fungilab rotational viscometer) protects the spindle and the
viscometer axle and it is important for the reading of low viscosities with standard spindles.
The protector should always be used. In the event that it is not used, its absence must be reported in the
measurement procedure notes.
The protector isn’t used with most of the accessories.
Speed selection and spindle
If there is no described work procedure, the best method for the selection of the spindle for each speed is
“trial and error”. The objective is a torque reading between 15 and 95%, according to the type of product in
question and a percentage higher than 50% is recommendable.
If you know the fluid’s approximate viscosity, the quickest spindle/speed selection method is referring to the
tables of maximum approximate viscosity.
When you do tests at different speeds, you should select a spindle with which all of the speeds show a
torque reading of between 15 and 95%
GENERALLY:
RPM INCREMENT READING PRECISION INCREMENT
SPINDLE SIZE-REDUCTION READING PRECISION INCREMENT
(Except for the non-Newtonian fluids that change their viscosity value when the rotational speed is
modified. In these cases we recommended measuring with a determined speed and using a comparison
method.)
Size of the sample container
For measurements using the Fungilab viscometer, we recommend working with containers with an interior
diameter of 83 mm or more. The usual container is a 600 ml precipitation vase.
If a smaller container is used, the viscosity values could be greater, especially with low-viscosity fluids.
Sample conditions
The sample should be free of air bubbles.
It should be exposed to a constant and uniform temperature. Before doing the viscosity readings, make
sure that the spindle and its protection are the same temperature. Usually, thermostatic baths are used to
maintain the sample at the desired temperature.
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