Cross-Section Mount
Definition
Embedding a paint chip in resin, polishing to a flat face, and viewing under reflected light at 100 to 400 times magnification to count and characterise individual layers.
- Preparation
- Paint chip embedded in resin and polished flat
- Viewing method
- Reflected light microscopy
- Magnification range
- 100 to 400 times
- Purpose
- Count and characterise individual paint layers
Common questions
Why polish the chip instead of just viewing it under a magnifier?+
An unpolished edge is uneven and light scatters off the torn surface, obscuring the boundaries between coats. Polishing exposes a flat, optically clean face so each layer's thickness, colour, and texture can be measured and compared with confidence.
What does the layer sequence in a cross-section mount tell an examiner?+
Vehicles and manufactured items are repainted in a known order at the factory and again if refinished, so the sequence of primer, basecoat, and clearcoat layers, along with their colours, can be compared against reference paint databases to narrow the source.
Related terms
- Binder
- The polymer matrix that holds pigments in place and bonds the paint to the substrate. Identifies paint type (alkyd, acrylic, polyurethane, epoxy)...
- Lacquer
- Clear or pigmented coating that dries purely by solvent evaporation (no chemical cure). Nitrocellulose and acrylic lacquers are the classic examples. Fast...
- Paint
- Pigmented liquid coating that dries to an opaque, coloured solid film. Built from four functional components: binder, pigment, solvent (vehicle), and additives.
- PDQ (Paint Data Query)
- RCMP-maintained international automotive paint database. Stores binder, pigment and layer data for vehicle original-equipment finishes from major manufacturers. Used to narrow a...
- Pigment
- Insoluble particles that give colour and opacity. Titanium dioxide (white), iron oxides (red/brown), carbon black (black), organic colorants (blues, reds). SEM-EDX reports...
- Pyrolysis GC-MS
- Heating a tiny polymer sample (about 1 microgram) to roughly 600 to 800 degrees Celsius in an inert atmosphere, separating the volatile...
- Varnish
- Transparent, hard protective film made from a drying oil, resin and solvent. Cures by oxidation (oil varnish) or polymerisation (polyurethane varnish). Used...