between the manufacturer of varnish products and their recipients - production companies (Wiśniewski, 1988). An advanced method of determining apparent viscosity is the Brookfield rheoviscometer. Varnish products experience different shear rates during application (Proszyk et al., 1995). Low viscosity varnishes are easier to spread, ensuring seamless coating, and are ideal for spray application. The lower the viscosity of the product, the thinner the layer. However, the coatings may have poor adhesion. The high viscosity of the products provides greater control over the process, but their application is more demanding. If the product’s viscosity is too high, the adhesion of the formed coatings may be incorrect due to the difficult distribution of the varnish. The condition for achieving good quality coatings is also proper preparation of varnishes by mixing them thoroughly. Insufficient mixing of the products results in uneven viscosity of the products. This results in the appearance of streaks, air bubbles and unevenness (Butt, 2022; Ozdemİr et al., 2013; Proszyk, 1999; Saranjam et al., 2016). Proszyk (1999) indicated the importance of the effect of temperature on viscosity. The annual temperature range in the production hall forces manufacturers to look for solutions that ensure constant conditions for the applied varnish (Schramm, 1998). Makarewicz (1991) observed that the components and their interactions have a significant impact on the shear behavior of liquids. Unstable viscosity in the process can affect the color and gloss of coatings due to uneven pigment dispersion as well as the orientation and distribution of matting agents (Makarewicz, 1991; Zheng and Chen, 2023). The aim of this work is to analyze the viscosity of industrially produced varnishes using two methods, with emphasis on its dependence on temperature. The results of the conducted research will be of significant importance for the manufacturing industry, indicating the need to control the application processes of paint products and improving the quality of final products. They will also contribute to understanding the mechanisms influencing the properties and performance of coating systems, which is crucial for the further development of technologies in this field. MATERIALS AND METHODS Materials The tests included acrylic varnishes: primer, basecoat and topcoat intended for UV curing in industrial conditions (Table 1). The manufacturer’s speciﬁed varnish composition is as follows: • Primer: calcium carbonate ≥ 40–<60%; ethoxylated propylidynotrimethanol, esters with acrylic acid ≥ 20–<40%; 4,4’-Isopropylidenediphenol, oligomeric reaction products with 1-chloro-2,3-epoxypropane, esters with acrylic acid ≥ 5–<10%; and 1-metoksypropan-2-ol ≤ 0.5%. • Basecoat: titanium dioxide ≥ 40–<60%, propylidinetrimethanol ≥ 10–<20%; 4,4’Isopropylidenediphenol, oligomeric reaction products with 1-chloro-2,3epoxypropane, esters with acrylic acid ≥ 5–<10%; alkoxylated pentaerythritol tetraacrylate ≥ 5–<10%; diacrylic dipropylene glycol ≥ 3–<5%; polymer based on polyoles and modiﬁed acrylic acid esters ≥ 2.5–<5%; phenyl-bis(2,4,6trimethylbenzoyl-)phosphine oxide ≥ 0.1–<1%; and 2-propenoic acid, 1,1’- [(1methyl-1,2-ethanediyl) bis[oxy(methyl-2,1-ethanediyl)]]ester, reaction products with di-ethylamine ≥ 0.1–≤0.5%. 106