| Observation | Diagnosis | Action | |-------------|-----------|--------| | Fine line widens then closes | Heat check in clear coat only | Sand to basecoat, recoat clear | | Widens and stays open | Crack through basecoat into primer | Strip to substrate | | No change, but visible line exists | Sand scratch, die line, or static crack (old damage) | Feather sand – no full strip needed | | Blister forms instead of crack | Solvent pop or moisture | Dry thoroughly, reseal | | Whitening without line | Cohesive failure in clear (over-cured) | Sand & recoat |