Refinishing and Paint Application
Refinishing and Paint Application
This domain tests paint system setup and application. Expect mixing ratios, viscosity, spray-gun setup, air pressure, booth conditions, sealer, basecoat, clearcoat, blending, colour match, tri-coat, and defect correction. The exam focuses on following the technical data sheet (TDS) and producing a uniform finish.
Core rules
- Read the TDS for mixing ratio, pot life, induction time, viscosity, gun setup, flash time, and cure. Do not substitute reducers or hardeners.
- Control booth temperature and airflow; cold paint may not flow, and poor airflow increases solvent exposure and contamination.
- Set the gun for the product: correct fluid tip, air cap, and pressure. Use a test pattern before spraying the vehicle.
- Apply sealer for uniform colour and adhesion, then basecoat in thin coats with proper overlap. Metallic and pearl colours require controlled application to avoid mottling.
- Blend within the adjacent panel when a panel-to-panel colour match is not possible; use blending solvent or a pre-blended base.
- Allow proper flash time between coats and before clearcoat; trapped solvent can cause solvent pop or dieback.
- Clearcoat the entire panel or blend area per the TDS. Do not polish until the coating is fully cured.
Worked example
A technician repairs a silver metallic door and plans to paint only the door. The vehicle's silver has a noticeable side-tone difference. Reasoning: silver metallics are sensitive to gun distance, overlap, and film build; a panel-only repair may not match under different lighting. The correct approach is to apply the base to the door and blend into the adjacent fender and rear door, using a drop coat to orient metallic, then clear the blended panels. The technician also checks the blend within the panel edge.
Traps
- Spraying with too much pressure and causing dry spray.
- Applying clear before the base has flashed.
- Using a generic reducer in a system with a specific one.
- Polishing fresh clear and dulling the gloss.
- Ignoring blend panels on metallic or tri-coat colours.
- Not cleaning the gun between products.