Viscosity is the resistance of liquids to movement or mixing. Kinematic viscosity is measured in Stokes and m2 / s. The viscosity of a material depends on its composition and the ambient temperature. It is clear that water-dispersion solutions will have a lower viscosity. But on the other hand, paints, for example, with the lowest viscosity, have a large coverage area and spread.
Use a special device. The viscosity is measured with a VZ - 246 viscometer (GOST 9070-75), which is used at a normal pressure of 0.1 MPa and a temperature of 20 ± 20C. This viscometer consists of a funnel of a certain volume and a nozzle of a certain diameter. The VZ - 246 viscometer measures the conditional (Newtonian) viscosity - the time of the outflow of a given material through a calibrated nozzle orifice, when the material is not subjected to any forces other than gravity.
Knowledge of the viscosity parameter is necessary for the selection of paints and varnishes in construction, the manufacture of oils and lubricants for technology, the printing of books and newspapers.
When purchasing paints and varnishes in a store, you can find out the viscosity of the selected product by reading its value on the package. However, if the packaging is damaged, it is quite possible to thin the paint with solvents, which leads to a deterioration in its performance, coating and drying. In this case, knowing the initial viscosity of the material, you can measure it yourself.
Take a cone-shaped funnel with a volume of 100 ml and a nozzle diameter of 4 mm. Install it strictly vertically.
Heat the material to be tested to a temperature of 20 ° C and pour it into the funnel. The funnel nozzle must be closed.
Open the nozzle and note the time it takes for the material to flow continuously from the funnel. The expiry time is the moment when the material stops flowing in a trickle and begins to drip.
When testing, it must be borne in mind that water-dispersion solutions are very sensitive to heat. A slight increase in heating temperature can increase the viscosity for a few seconds.