When printing adhesive labels, the UV varnish coating is uneven, and the cured coating does not show mirror. First, the label should pay attention to when using polishing oil: 1. Understand the types, properties, effects of polishing oil and the changes in preparation with other solvents. 2. Choose the suitable varnish according to the surface properties of the substrate and ink. 3. Attention should be paid to the drying performance of polishing oil. Does the drying temperature range and drying time affect the printing material? 4. Consideration should be given to the post-processing adaptability of polishing materials, such as hot stamping performance, durability of friction, pressure resistance of concave-convex indentation die cutting, etc. 5. The polishing oil with high transparency and low odor should be selected.