Types of viscometers for paint, how viscosity is measured and how to determine it

The viscosity of the paint characterizes its suitability for use. Also, additional properties depend on it - the brightness of shades and the uniformity of the coating. In order to paint the surface evenly, it is important that the material flows normally. However, it must not flow. This indicator also affects the technical characteristics of the coating. It requires the use of a paint viscometer to measure it.

The concept of the unit of paint viscosity

Viscosity is understood as the characteristic property of liquid materials to resist the movement of one part of it relative to another during flow. Given the composition and the rules for applying to the surface, the dyes must have a certain texture.

A special device called a viscometer is used to determine the viscosity parameters. It looks like an open funnel in the shape of a cone. It is directed downwards with a point. There is a hole of a specific diameter.

Why viscosity is measured in seconds

Russian companies use seconds to measure viscosity. Foreign brands use a different parameter - DIN.The time in seconds is measured during which a specific volume of paint flows through the hole. In this case, the flow of liquid paint is faster, and thick - slower.

Influence of paint viscosity on properties

Viscosity affects key characteristics of colorants. It is important to consider the following characteristics:

1. A dye that is too viscous is difficult to apply in a thin layer on the surface. Excessive thickness increases drying time and reduces coating strength parameters.
2. Too thick a substance is not able to fill the qualitatively small irregularities that are at the base. This leads to a sharp deterioration in the adhesion of the dye to the surface.
3. Paint that is too thick on vertical surfaces will cause sagging. The same is true for inclined structures.
4. The majority of cheap spray guns are not able to cope with too viscous substances. The operating characteristics of an airblast sprayer are based on low pressure in the air stream. The paint is sucked from the container. When using a very thick dye, this process is disrupted. In such a situation, the device will have to be disassembled and washed. It is recommended to do this with a solvent.
5. Liquid paint does not damage the tool. It deposits evenly on the surface. However, too liquid a consistency leads to an increase in coating layers. This increases the drying time.

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How to Measure LCI Viscosity Using a Viscometer

To determine the viscosity parameters, a viscometer is needed. To do this, it is recommended to perform a few simple steps:

1. Fill the funnel.In this case, it is recommended to close the outlet with a finger.
2. Open the hole and start the stopwatch at the same time.
3. Record the time it took to empty the container.

It is important to take measurements at temperatures of + 18-22 degrees. With a decrease in the parameters, the materials thicken, and with an increase they become more liquid.

When using two-component substances, a different technique should be used. To obtain optimal viscosity parameters, you should do the following:

1. Mix the paint with the hardener. In doing so, it is recommended to strictly follow the manufacturer's instructions. Too little or too much hardener will have a negative effect on coating strength.
2. Check the viscosity with a viscometer. If necessary, the material should be further feathered to achieve a working texture.

To measure the required amount of base and hardener, follow these steps:

1. For small quantities, it is worth using volumetric dishes.
2. In a bulky cylindrical container, it is worth using a special scale. If the height of the dye level reaches 40 centimeters, then adding a substance up to 50 centimeters will help to achieve a ratio of 1: 4.

It should be borne in mind that this method gives reliable results only in cylindrical vessels. An ordinary bucket has the shape of a truncated cone. This causes a distortion of the proportions.

For the measurement of the viscosity parameters to be correct, it is recommended to observe the following rules:

1. It is worth measuring the viscosity of materials several times during dyeing. Depending on the values ​​obtained, you can adjust the texture. If the consistency is too thick, it is recommended to introduce a solvent into the mass. If the viscosity is too low, the volume of the colorant is increased.
2. Do not measure if the mass is foamy. This will prevent accurate results from being obtained.
3. If a primer is needed before painting, its conditional viscosity should be checked with a viscometer. In this case, it is recommended to use a device from the B3-246 series. In this case, the diameter of the device hole should be 4 millimeters. Satisfactory parameters are at the level of 12-18 seconds.

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Varieties and characteristics of devices

There are several types of such devices, which differ in their principle of operation:

1. Rotating - these models include 2 rotating objects. The test material is placed between them. Then one part of the device is rotated, and the other is left motionless. By the speed of rotation between them, it is possible to determine the absolute viscosity.
2. Capillary - these devices work on a chronometric basis. They help determine the time it takes for a given volume of fluid to pass through a small hole or tube. This uses the specific pressure difference. In appearance, the device looks like one or more capillaries that are attached to each other. They have a small filling opening or tube.
3. With a moving ball - Stokes' law is the basis for the operation of such devices. The determination of viscosity parameters is based on the time interval during which the ball travels a specific distance under the influence of its own weight.
4. Vibration - measurements are based on the change in resonant frequency of vibration in a liquid medium. In some devices, it is possible to adjust the density regardless of the viscosity. In other devices, the parameter is measured at constant density.
5. Bubble - determine the movement of gas bubbles moving smoothly to the surface in a thick medium.According to these indicators, the viscosity of the material is found.

If you have to choose the right device, it is worth considering all the properties and functionality of each option. In addition, today there are many models.

The most optimal values

The required dye viscosity parameters are usually indicated on the packaging. Also, this information can be found on the manufacturer's website.

At the same time, there are universal recommendations suitable for different types of paints and varnishes. They are shown in the table:

Type of coating	Viscosity, seconds
Textured substances	15-25
Oil-based glazes and stains	15-25
Primer	15-30
Latex substances	35-45
Automotive paint enamels	15-20

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If there is no viscometer, it is worth considering the following rule: it is recommended to dilute the bulk of household dyes to the consistency of fatty milk. In this case, the type of thinner is indicated on the packaging.

Any violation of the indicators recommended by the manufacturer leads to difficulties in applying the coating. If the liquid is very viscous, it will not be able to pass through the tool hole. This will result in uneven application of the substance. At low settings, the enamel begins to flow. This leads to the appearance of divorces. Also, areas may form that have not been painted over.

The viscometer is considered to be an efficient device that is often used to measure the viscosity of dyes. This makes it possible to evaluate the properties of the material and, if necessary, to bring it to the desired texture using solvents.