## 4 Discussion
The focus was increased to 0.5 mm, which resulted in a larger-sized individual dimple. The approximate diameter of a single dimple is 0.48 mm. Dimples are spread evenly and do not overlap. The distance between the edges of the dimples is less than 0.05 mm. No local burns were noticed during the texturing process. Some local damage caused by sparkles can be noticed on the surface layer. One of them is clearly visible in Figure 5b. The texturing path is repeatable. Sample no. 4, presented in Figure 6, was also melted in a regular manner and the individual dimples did not overlap. Even though the focus was set to 0.5 mm, the final diameter was no more than 0.3 mm. The distance between individual meltings was much  
Figure 4: Microscopic observations of sample no. 2: (a) 10\(\times\) magnification by ZEISS; (b) 50\(\times\) magnification by Olympus; and (c) 100\(\times\) magnification by Olympus. Figure 5: Microscopic observations of sample no. 3: (a) 10\(\times\) magnification by ZEISS; (b) 50\(\times\) magnification by Olympus; and (c) 100\(\times\) magnification by Olympus. larger when compared to others. They varied from 0.5 mm to almost 2 mm. The path looked regular. It was repeatable up to a point where some distraction occurred, after which there was a path shift. The cause of the shifting remains unknown. It was assumed that there could have been some vibration in the building caused by a passing truck or some experiments conducted in an adjacent laboratory. The fifth sample, presented in Figure 7, was created with increased frequency. Microscopic observations revealed some local burns which were not as intense as those in the first sample. A clear higher magnification image of this sample proved difficult to obtain. The estimated size of an individual dimple is 0.4 mm. The dimples overlap with a regular patterned edge. Sparkle formation caused visible damage to some areas of the sample. After increasing the laser power and the modification area it was observed that the lack of sample preparation produced some problems, such as  
* Increased spark formation, which led to the destruction of the already applied path;
* Irregular shape of individual dimples;
* Local material burn-throughs;
* Deformation of the sample and upward bending during the remelting process caused by heating with the laser beam;  
The observed undesirable side effects of the laser melting process were a motivating factor to take action to prepare the sample surface before exposing it to the laser beam. The sample preparation is an important, although rarely described in detail process. The literature data provide young scientists with only general statements, such as 'polished', 'cleaned' or 'etched', without a detailed description of the applied sample preparation methods. [PERSON] et al. mention that their copper samples were polished [20]. Pou  
Figure 6: Microscopic observations of sample no. 4: (**a**) 10\(\times\) magnification by ZEISS; (**b**) 50\(\times\) magnification by Olympus; (**c**) 100\(\times\) magnification by Olympus. Figure 7: Microscopic observations of sample no. 5: (**a**) 10\(\times\) magnification by ZEISS; (**b**) 50\(\times\) magnification by Olympus; and (**c**) 100\(\times\) magnification by Olympus. et al. used ultrasonical cleaner, ethanol, acetone, and distilled water both before and after laser treatment [10]. On the other hand, [PERSON] et al., in their literature review [2], claimed that effective laser ablation can be applied directly to the surface, without any need for additional pre-treatment, chemicals, or masking layers, which they take as an additional merit of reducing the overall process steps. Attempts were made to grind, etch, and darken the sample surface. Standard sample preparation procedures were used for macroscopic tests based on the 'Metaloznawstwo: materials for laboratory exercises' script commonly used at the Gdansk University of Technology [24; 25].