Three-Stage Pearl White Variant Match on a Fender Blend
A 2021 SUV in three-stage pearl white needs a right front fender repair and a blend into the right front door. The color code lists three variants: A, B, and C. The camera-selected variant B produces a spray-out that is grayer and darker at face than the door, but under the shop's LED lights it looks close. In daylight the pearl lacks sparkle and looks muddy. The technician sprayed a let-down card with 2, 3, and 4 coats of midcoat over the base; 2 coats look too white and 4 coats look too yellow. The door has an old repair with a hard tape line. The midcoat gun is a 1.3 mm HVLP at 26 psi, and the technician's distance varies from 10 to 30 cm. Booth temperature is 24 degrees C. The shop has blend prep cleaner, a color-corrected lamp, and a mixing bank but no spectrophotometer.
1. How would you determine whether the problem is variant selection, midcoat film build, or application?
Read the worked answer
Separate the three variables. First spray the base color alone on a card and compare it to the door's base under daylight and a color-corrected lamp; if the base is off, no amount of midcoat will fix it. Then use the let-down card: 2, 3, and 4 coats of midcoat show that film build is shifting the color from too white to too yellow. Pick the midcoat coat count that matches the door at both face and flop; if none matches, the variant is wrong or the base needs a tint. The camera's variant B looking gray and dark at face but close under LED points to metamerism and a variant miss. Finally, the 10 to 30 cm gun distance can cause mottling, so standardize distance and overlap before judging the card.
2. Describe the blend procedure for the fender-to-door repair, including treatment of the old tape line.
Read the worked answer
Repair and prime the fender; seal if the tech sheet requires. Apply base to the fender and blend base into the door, keeping the base wet enough to avoid a dry edge. Apply the midcoat over the fender and extend it into the door in a tapered overlap, using the coat count selected on the let-down card. Clear the entire door or use a wet blend within the door, not a hard tape line. The old tape line must be sanded flat with 400 to 600, feathered, cleaned, and treated with blend prep before recoating; otherwise it will telegraph and leave a halo. Keep gun distance, speed, and overlap consistent, and use a slow-enough reducer for 24 degrees C.
3. What test would you use to choose the final midcoat coats, and how would you document the match?
Read the worked answer
Use a let-down card sprayed with the chosen base and stepped midcoat passes, then compare it to the adjacent door in daylight, not only LED, at a 45-degree face and a lower flop angle. Record variant, midcoat coat count, gun setting, pressure, distance, booth temperature, and product lots on the job card. If the card matches but the repair does not, application is the variable. Keep the card with the vehicle or photograph it for the file.