Foreign particles in paint are small particles that are randomly spread on the surface of the paint film that interfere with the appearance of the dried paint film. They can be caused by not dispersed or agglomerated pigment particles, dirtiness, resin gel fractions, pigment agglomerates and precipitated resin due to solvent shock or reaction products that may occur from reactions between zinc oxide active pigments and other paint ingredients or impurities. The source of the problem should be determined before attempting to resolve the foreing particle paint defect. However, if the particles do not appear in the original paint but appear during storage, it may be difficult to determine the root cause 

Fig.1: Particle samples in an air drying alkyd paint

Fig 1.

Potential causes of particle formation can be dirt left in the production equipment, poor general cleanliness and order in production facility, raw materials which are out of specification, insufficient grinding or insufficiently stabilized dispersion, incompatibilities between paint components and excessively rapid let down process. The dirtiness of the pipelines used for transfer purposes or the pumping of incompatible material without adequate intermediate cleaning can also lead to the presence of particles in paint production process.

Fig 2.

If the particles can be observed at the end of production, it may be possible to eliminate them by filtering. A better solution would be to identify the reason behind the particle occurence and to refine the production process from this effect. Attention should be paid to the cleanliness of the paint packaging Fig.2: Analysis samples of the materials on the sieve after the filtration process before application.

Fig 3.