## 3 Results
### Gloss Level  
A Pareto effect size plot in standard deviation was determined for the gloss results (Figure 8). It was found that the amount of the applied topcoat, the abrasives used and the number of applicators had the greatest effect on the achieved surface gloss (effect size larger than two). The next two factors are UV mercury lamp power and the amount of the basecoat (between 1 and 2). The type of board and the LED lamp power did not affect this parameter. The main effect plots describe the gloss change direction under individual factors' influence. Applying a topcoat at 3.0 and 6.5 g/m\({}^{2}\) had no significant effect on the analysed ratio. An increase of a further 3.5 g/m\({}^{2}\) resulted in a very sharp increase of almost 10 gloss level units. Using finer abrasive grit size and a greater number of applicators helped increase the recorded gloss values on the coating. Curing with mercury lamps in the intermediate power variant (90 W/cm) resulted in the lowest parameter, while the highest parameter was obtained for 120 W/cm. The gloss decreased as the amount of the basecoat increased. The higher-density HDF board achieved a slightly higher gloss level. The line is horizontal (parallel to the \(x\)-axis) for LED lamp power, so there was no main effect. Analysing the Pareto chart of the standardized effects for interactions, the only statistically significant interaction was that between the amount of the topcoat applied and mercury lamp power (Figure 9). When 3 g/m\({}^{2}\) of topcoat was applied, the gloss level was  
Figure 8: Main effects and Pareto effects plots for gloss level. similar for the surfaces cured with mercury lamps at 60 W/cm and 120 W/cm. The lowest values were achieved at 90 W/cm. The gloss level increased by applying 6.5 g/m\({}^{2}\), with the lowest increase recorded for curing with mercury lamps at 60 W/cm. The gloss increased as the lamps' power increased. A further increase for all curing variants proceeded at the same rate. Based on these, the author concluded that a thicker coating layer increases the coating resistance. This is consistent with the information provided on quality improvement when more topcoat is applied [54, 55]. However, the same principle was not used with the priming varnish. The functions of varnishes need explanations. The basecoat varnish's chemical composition is designed to provide the varnished surface colour, guarantee evenness and provide initial resistance. The fundamental goal of a topcoat is to guarantee a quality finish. According to other reports, the ratios of the materials, the types of resin employed and other additives affect the scratch-resistant coatings [56]. There is a close relationship between the material after grinding and the coating [57], and that was confirmed by determining the effect of grinding on the surface gloss. It has been repeatedly proven that a gloss reduction occurs with an increase in roughness [58, 59], which is provided by a smaller material grain size [43, 60, 61]. Overly aggressive grinding exposes the substrate structure, which can be filled with glue, thereby contributing to a reaction with the applied varnish layer [62]. The roughness of the first basecoat layer increased linearly, and the adhesion decreased for finer abrasives [13]. The cases described confirm the increase in gloss as the abrasive's grain size increased before and after grinding. In the literature, it is also possible to find publications on the increase in gloss with the application of successive varnish coats [45]. Lower gloss was observed with higher topcoat thickness when finishing using conventional UV lamps [55]. This may be due to differences in the composition of varnishes cured by mercury lamps and LED lamps. The researchers also conducted a comparative gloss study after scratch resistance tests of 200 cycles for coatings cured with LED and conventional UV lamps. No difference in gloss loss was noticed between the technologies [52].