Theoretical part
Viscosity is the internal friction that occurs between fluid layers when they move
against each other under the influence of appropriate mechanical stress. The viscosity
of paints must strictly correspond to the speed of the printing process. The viscosity of
the paint depends on the nature and properties of the binder and the size of the pigment
particles.
The larger the liquid molecules are, the greater their contact surfaces, the greater
the friction between them and the higher the viscosity.
Work order
The working life of the binder viscosity is determined by the method of dropping
steel balls. A glass tube (cylinder) with a capacity of 250 ml is filled with water to the
bottom line. Two lines are drawn on the walls of the tube at a distance of 200 mm from
each other. Water is not used when testing transparent varnishes.
A steel ball with a diameter of 2 mm is gently thrown into the cylinder with a
clamp, and with a stopwatch it is determined how long it takes for this ball to fall
freely through a layer 200 mm thick.
The test is carried out 3 times, and the arithmetic mean value indicates the
conditional viscosity in seconds.
Job report
1. How does the viscosity of the paint affect the quality indicators.
2. Make a conclusion based on the results of conditional convergence.
Control questions:
1. What indicators are related to paint viscosity?
2. How is the "Conditional margin" indicator determined?
3. What substances are used as binders?
4. What distance must the steel balls travel?
8 - LABORATORY WORK
EVALUATION OF COLOR INDICATORS USING EQUAL-CONTRAST
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