Pigment
Definition
Insoluble particles that give colour and opacity. Titanium dioxide (white), iron oxides (red/brown), carbon black (black), organic colorants (blues, reds). SEM-EDX reports the elemental fingerprint.
- Key Pigment Colors
- White (titanium dioxide), red/brown (iron oxides), black (carbon black), blue (phthalocyanine), green (chromium oxide)
- Detection Method
- SEM-EDX analysis reveals the elemental fingerprint of pigments in paint samples
Common questions
What role do pigments play in paint evidence?+
Pigments are the insoluble particles that give paint its color and opacity. By identifying which pigments are present using techniques like SEM-EDX, forensic analysts can create an elemental fingerprint that helps distinguish paint samples from different sources.
What are some common pigments used in coatings?+
Typical pigments include titanium dioxide for white, iron oxides for red and brown shades, carbon black for black, phthalocyanine blue for blue, and chromium oxide for green. Different pigment combinations help forensic examiners differentiate paint samples.
Why do forensic examiners analyze pigments in paint cases?+
Pigments are insoluble, durable particles that survive in paint layers and retain their composition. Their elemental makeup and specific combination can link a suspect's vehicle or clothing to a crime scene when paint transfer occurs.
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)...
- Cross-Section Mount
- Embedding a paint chip in resin, polishing to a flat face, and viewing under reflected light at 100 to 400 times magnification...
- E-Coat
- Electrocoat primer, the first layer applied to a clean steel/aluminium substrate via cathodic electrodeposition. Usually black, epoxy-based, near-universal on modern automotive bodies.
- 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 database (RCMP-maintained). Cross-referenced from glass work when a vehicle is identified through paired glass and paint evidence.
- 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...
- Py-GC-MS
- Pyrolysis gas chromatography mass spectrometry. Thermal decomposition of a paint sample, separation of fragments, mass spectral identification. Definitive identification of polymer binders.
- 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...
- Refinish
- Aftermarket repaint applied at a body shop, distinguishable from OEM (original equipment manufacturer) paint by layer count, binder chemistry, and application technique.
- Varnish
- Transparent, hard protective film made from a drying oil, resin and solvent. Cures by oxidation (oil varnish) or polymerisation (polyurethane varnish). Used...
Explained in these topics
- Paint Evidence: Layers, Coating Structure and Instrumental AnalysisInsoluble particles that give colour and opacity. Titanium dioxide (white), iron oxides (red/brown), carbon black (black), organic colorants (blues, reds). SEM...
- Paint, Lacquer and Varnishes: Nature, Composition and Forensic ExaminationInsoluble particulate that gives the coating its colour and opacity. Examples: titanium dioxide (white), iron oxide (red, yellow, brown), carbon black, phthalo...