Silver Metallic Door Looks Lighter Outdoors
A three-year-old silver metallic hatchback has a repaired right front door. The painter used the manufacturer colour code, a 1.4 mm gravity-feed gun, 3 bar at the gun, a 15 cm distance and 50 percent overlap. The door was prepared with P400 abrasive, sealed, base-coated in three coats and clear-coated. In the booth the door looked correct. Outside in daylight the door is lighter and flatter, the metallic appears coarser, and there is a dark band at the front edge next to the original wing. The adjacent wing has slight fade. The shop has a spectrophotometer, variant chips, a range of thinners, a blending solvent and a test panel, but no let-down panel rack. The customer will not pay for a full side respray. The booth temperature is 30 degrees Celsius and humidity is high. The painter plans to polish the door harder to make it darker.
1. Diagnose the likely causes of the mismatch and explain why harder polishing will not correct it.
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The door is probably too light and flat because the metallic is not oriented like the original, not because the colour code is wrong. Causes include too much film build, a fast thinner at 30 degrees Celsius, dry spray from 15 cm and 3 bar, inconsistent overlap, a sealer shade that is too light, and no blend into the faded wing. The dark band at the front edge is a tape or edge line from dry overspray. Polishing cannot reorient metallic and may remove the clear or make the edge worse. The spectrophotometer reading is only a starting point; the wing has faded, so the variant must be checked on the car.
2. Describe the colour-match and blending procedure you would use with the equipment available.
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Wash and degrease, then use the spectrophotometer on the door and the adjacent wing, and spray a test card or let-down panel with the chosen variant and one or two alternates. Compare in daylight, not only booth light. Adjust the variant or tint if needed. Seal the repair with a matched sealer; apply base in thin, wet, uniform coats with a 1.4 mm gun at the data-sheet pressure, typically around 2 bar at the gun, and 15 to 20 cm distance, 50 percent overlap, keeping the gun perpendicular. Use a slower thinner or retarder for the high temperature and humidity. Blend the base into the wing with a soft edge and blending solvent, then clear the whole door and blend clear onto the wing. Do not tape a hard line at the front edge.
3. What final quality checks would you make before delivery, and what would you do if the match is still out?
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Before delivery, check the panel in daylight from several angles, including a low angle for metallic flip, and compare with the wing. Look for mottling, coarse metallic, dry spray, tape edges, runs, dirt and gloss difference. Check film thickness and adhesion on a test area. If the match is still out, do not polish harder; recoat with the correct variant or blend further. Also check that the clear has not been over-thinned, because that would reduce durability and gloss.