Short answer
Both are platelet pigments that work only when the flakes lie flat, parallel to the surface. Metallic pigments are thin flakes of aluminium or other metal that mirror light in one direction, so a metallic finish is bright near the reflection angle and darker away from it — the effect called flop. Pearlescent pigments are transparent platelets, typically mica, coated with a thin layer of titanium dioxide or iron oxide, which reflect part of the light and let the rest through, giving a soft lustre and, depending on layer thickness, interference colour.
An effect pigment is a platelet: metal effect flakes are typically around 20 µm across and at most about a micrometre thick. In a well-applied coating they settle parallel to the surface, each acting as a tiny mirror. Light arriving at the surface is reflected mostly in the specular direction; seen from near that direction the coating is bright, and seen from a steep angle to it most of the light has gone elsewhere and the coating looks darker, with scattering from flake edges contributing what remains. The change of lightness with viewing angle is called flop or brightness flop. Larger flakes add visible glints — sparkle — whose appearance depends on the lighting geometry, and a dark base colour increases their contrast.
Natural pearl and fish-scale lustre comes from stacks of thin transparent layers, each reflecting a little light. Pearlescent pigments imitate that with transparent platelets — mica, and also synthetic alumina, silica or glass flakes — coated with a high-refractive-index oxide, usually titanium dioxide or iron oxide. Each coated platelet reflects part of the light at its surfaces and transmits the rest to platelets beneath, so the reflection seems to come from within the film, which the eye reads as depth and lustre rather than as the hard glitter of metal. With iron oxide, the coating also absorbs, giving bronze and copper tones; with titanium dioxide alone, the colour comes entirely from interference in the coating, described on the interference pigments page.
Because the colour of an effect finish changes with both illumination and viewing angle, a single measurement or a single glance cannot describe it. Two panels can match face-on and part company at a grazing angle if their flakes differ in size, orientation or concentration, or if the paint was sprayed with different settings that change how flat the flakes lie. Historically this made invisible repairs of metallic car paint notoriously difficult. Industry measures effect finishes with multi-angle spectrophotometers that record colour at several aspecular angles, and matches are judged by moving the panel under a light rather than looking straight on. The measurement pillar's page on geometry explains why angle matters to every colour measurement.
Metallic and pearlescent finishes are standard in car paint, where a basecoat carrying the effect pigment and transparent colour is protected by a clear coat, and they are common in plastics, printing inks, cosmetics and decorative paints. Aluminium pigments in inks and coatings give silver effects; tinted with transparent colour layers, they give coloured metallics. Pearlescents appear in nail varnish, eye shadow, packaging, and the white pearl paints that became popular on cars. The vehicles pillar compares solid, metallic, pearlescent and matte car finishes; this page is about the pigments themselves. Metallic-effect decorative paints for walls and furniture use the same principle at a coarser scale, and depend even more on the direction of the light in the room.
| Family | Structure | What the eye sees |
|---|---|---|
| Metal effect (aluminium, bronze) | Opaque metal flakes | Mirror-like brightness near specular, darker away: strong lightness flop |
| Pearlescent (oxide on mica) | Transparent platelet with a thin TiO₂ or Fe₂O₃ coating | Soft lustre with depth; interference colour set by coating thickness |
| Alumina- or glass-flake effect | Smooth synthetic platelets with oxide coatings | Cleaner reflections and stronger sparkle |
| Multilayer colour-shifting | Several thin layers of alternating index | Large change of hue with angle (see interference pigments) |
Why: Flake size, concentration or orientation differs from the original, so the flop does not match.
Fix: Judge repairs at several angles under a single light and blend the new paint into adjacent panels.
Why: Brush or roller direction changes flake orientation from stroke to stroke.
Fix: Apply in consistent directions, keep a wet edge, and check under the room's real light direction.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactModerate evidence
Effect pigments are platelets whose optical effect depends on their orientation; metal effect pigments reflect directionally when aligned parallel to the surface, so a coating looks bright at steep viewing angles and dark at shallow ones, a variation called brightness flop.
Source: Effect pigment
FactModerate evidence
Pearlescent pigments are commonly mica or alumina platelets coated with titanium dioxide or iron(III) oxide, and the thickness of the oxide layer determines the interference colour.
Source: Titanium dioxide; Effect pigment
FactModerate evidence
Flop in metallic paint is caused by the size and reflectivity of the flakes and by their orientation and alignment, which historically made invisible repairs difficult.
Source: Metallic paint
FactModerate evidence
Interference and pearlescent pigments were reviewed as a class of angle-dependent optical materials deriving from submicron layer structures.
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.