A paint depth meter is a small electronic device that measures the thickness of paint on a metal panel. They cost $50 to $300 depending on quality and capability. For anyone serious about buying a classic or performance car, one of these devices is as important as a torch.
What a paint meter measures
A quality paint meter measures the total thickness of all coating layers on a panel: primer, base coat, and clear coat. The reading is expressed in microns. Standard factory paint on a modern car typically measures between 90 and 175 microns depending on the manufacturer. What you are looking for are readings that deviate significantly from the baseline.
How to take readings
Take multiple readings across each panel. Not one reading per panel but five to ten, distributed across the surface including corners, edges, and the centre.
Take readings on panels that typically remain original as reference points. The roof on most cars receives minimal accident damage and often has near-factory paint thickness. Establish your baseline for this specific car on these panels before you interpret readings elsewhere.
What elevated readings mean
A panel reading significantly above your established baseline has additional material on it. The most common causes are a full respray where the original paint was not stripped before new paint was applied, body filler applied over repaired damage (readings of 400 microns or more in a localised area almost certainly indicate filler), or multiple resprays.
What uniform readings mean
Here is the counterintuitive observation: perfectly uniform readings across every panel of an old car are not necessarily a good sign.
A car that has genuinely lived its life without panel damage will have variation in its paint readings. Different panels were painted at different temperatures, the spray line applied slightly varying thicknesses, the door edges and body shut lines differ from the panel centres. Small variation is normal.
A car with precisely uniform readings across every panel has sometimes been prepared to show consistent readings. Consistent variation within a normal range is a good sign. Suspicious uniformity warrants additional scrutiny.
What a paint meter cannot tell you
A paint meter tells you paint thickness. It does not tell you whether there was structural damage. A panel that was straightened, filled, and resprayed can show elevated paint readings but the structural repair beneath is not visible to the meter.
Physical inspection of the panel for ripples, waviness, or inconsistency in surface texture is necessary alongside the meter readings. Run the back of your hand along a panel. A properly repaired panel is smooth and consistent.
Combining the paint meter with visual inspection
Use the meter to identify panels with elevated readings. Then inspect those panels with increased attention. Check door apertures for paint overspray on rubber seals. Check boot hinges for colour match inconsistency. Check panel gaps for uniformity.
A panel that reads elevated on the meter and has evidence of masking on adjacent rubbers and a colour match that is fractionally off is a panel that was resprayed after an incident. Three signals together is a confirmed finding.
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