Page 117 - 20250602 EEA QM Edition 6.0

Quality Requirements Edition 6.0 European Enamel Association

8.5.4.4 Determination of the flow-characteristic of enamel slips by means of rotary 8.5.4.5 Determination of the flow-characteristic of enamel slips by means of
viscosity meters
viscosity testers

Purpose and scope
Purpose and scope
The principle of rotary viscosity meters in combination with coaxial cylinder-
Viscosity testers are rotary viscosity meters, with which one is able to measure the
measuring systems allows the absolute measurement of single flow-characteristics.
torsional shearing stress with the help of given velocity gradients. According to
In the ring slot, between the plates formed to cylinders, there is the to be measured
construction and measuring-system, the measurements are directly comparable to
liquid. By a defined motion of the cylinders against each other and a measurement
continuous working devices. Due to the fact, that viscosity testers are only able to do
of the appearing forces, the measuring problem can be solved in a mathematical point determinations, no flow diagram is available. As a measuring system, the Searle-
way.
system is used predominantly. The adjustable velocity gradient steps should be in-

between 75 to 600 s .
-1
One distinguishes from two forms in the execution of the measuring system:

Viscosity testers provide very good measurements for the internal control of
1. The Searle-system: The inner cylinder (body of revolution) rotates with a constant
enamel slips.
or variable rate of revolutions, while the outer cylinder (measuring beaker) is in a
fixed state. The liquid in the ring slot flows and generates a torque, that is directly
depending on the liquid’s viscosity.

2. The Couette-system: The outer cylinder rotates and makes the liquid in the ring
slot flow. The resistance of the liquid against the shearing action transfers a directly
on the viscosity of the liquid depending torque onto the inner cylinder.

Details of standard measuring-systems are described in DIN 53018.

The relation between the torsional shearing stress and the velocity gradient are
nowadays automatically seized in a flow diagram. Out of this, the flow-characteristics
of a liquid or a mud can be seen. Because of the fact, that most of the laboratories
are equipped with desk calculators, single measurements can be printed and can be
compared to one another.

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