Should touch-up painting be done in a small or large area?

[EmmanuelFitz]

Touch-up painting should only cover the necessary area. Below is the process for touch-up painting: 1. Determine the repair area: Carefully inspect the damaged area. If the damage exceeds one-third of the component, a blending repair method should be used. Blending repair involves applying clear coat over the entire component while transitioning the base coat from the damaged area to the original paint. This maximizes the retention of the original paint and avoids color mismatch issues. If the damage exceeds one-third, the processes of sanding, priming, base coat, clear coat, and blending will cover more than two-thirds of the component, leaving little untouched area and making the repair less meaningful. 2. Surface preparation: Mix an appropriate amount of body filler and hardener based on the size of the damage (ratio: 100 parts body filler to 2-4 parts hardener, adjusted according to temperature). Fill the dent or scratch firmly, then use a scraper at a 45-degree angle to level the surface slightly above the component. Use an iodine-tungsten lamp to speed up drying. Once dry, sand with P320 grit sandpaper to level, then with P800 grit for smoothness before applying primer. 3. Masking and degreasing: Use an air gun to remove moisture and dust from component gaps, then carefully mask non-painted areas with masking paper. Wipe the painted area with a paper towel dipped in degreaser, followed by a tack cloth with an air gun for thorough cleaning before applying the base coat. 4. Base coat application: Dilute the mixed base coat thoroughly (1:1 ratio with thinner) and filter it. During spraying, control the spray area, set the air pressure to 2KPa, and use a dry spray technique. After each coat, wipe with a tack cloth. Gradually transition from covering the primer outward until no color difference is visible.