Viscosity is essential for Paint: Control and Application
Viscosity is a critical parameter in the manufacturing and use of industrial paint. It influences product stability, the quality of the applied film, and process reproducibility. To control this parameter, a viscometer is an indispensable tool, whether in formulation, production, or on the application line.
1. Understanding the role of viscosity in Paint
The viscosity of a paint is not constant: it varies according to shear conditions, temperature, humidity, and formulation.
Therefore, controlling viscosity is essential to ensure:
• Storage stability (preventing sedimentation or phase separation)
• Good application properties (neither too fluid nor too thick)
• Uniformity of the applied film (thickness, gloss, color)
2. Paint Manufacturing: Viscosity at every stage
2.1. Standard Composition
Paint is generally composed of:
• Binders: synthetic resins that ensure the cohesion of the dry film
• Pigments: provide color, opacity, and functional properties
• Additives: improve stability, rheology, or other specific characteristics
• Solvents: adjust viscosity and facilitate application; they evaporate during drying
Each of the listed ingredients directly affects the overall viscosity of the mixture.
2.2. Production steps
Preparation: Preparation starts by weighing raw materials (liquids and solids). A proper dosing is essential for formulation.
Dispersion and Grinding: These two steps allow to create a homogeneous paste. A Well-adjusted viscosity allows for an efficient dispersion.
Viscosity Adjustment: In order to adjust paint viscosity, the difference between target viscosity and measured viscosity is determined using a viscometer. Depending on the result, a solvent or thickener can be added. Historically, viscosity measurement was carried out with a laboratory viscometer or a rotational viscometer. Sofraser, pioneer in vibrating technology, offers two solutions for paint viscosity measurement: the MIVI or the Sofine.
Color Tinting: The addition of color bases can modify the paint viscosity; adjustment may be necessary to meet specifications.
Packaging: Before filling, the paint is filtered. Viscosity must remain stable to avoid variations during storage.
3. Paint Use and Application
3.1. Influence on Spraying
Spraying consists of transforming paint into a mist by atomization.
The droplet size depends on viscosity and nozzle diameter.
Consequences of improper viscosity:
• Too fluid: drips, insufficient opacity
• Too viscous: droplets too large, uneven coverage
Well-adjusted viscosity ensures:
• Uniform distribution
• Good adhesion
• A stable paint film, free from defects
3.2. Quality Control on the Line
After application, viscosity influences:
• Film thickness
• Adhesion to the substrate
• Visual appearance (drips, craters, orange peel effect)
A continuous viscosity measurement ensures these criteria remain within tolerance.
3.3. Recirculation Loop
On an industrial application line, paint is often pumped in excess to supply the nozzles or spray guns. The excess is collected and returned to the tank in a recirculation loop.
Viscosity control allows management of the following risks:
• Solvent loss due to evaporation
• Viscosity changes caused by agitation or product aging
3.4. Inline Measurement with a Sofraser Coating Viscometer
Integrating a MIVI viscometer in the loop enables:
- Continuous measurement without production interruption
- Automatic control (addition of solvent or thickener if necessary)
- Process stability, and reduced waste
The MIVI, with its vibrating technology, improves the efficiency of your manufacturing process.
Viscosity is involved at every stage of paint processes whether it is during formulation, manufacturing or application. It directly affects the product quality and behavior in use.
Sofraser vibrating viscometers, such as the MIVI, provide reliable, continuous, and precise measurements, perfectly suited for industrial environments. By integrating them into production or spraying lines, they ensure complete process control and the quality of final products.
