Industry-Grade Pearl Pigment for Coatings and Plastics: Grade and Particle-Size Selection

Industrial buyers rarely choose an effect pigment by colour alone. They choose by particle size, because particle size is what determines whether the finished part reads as satin, pearl or sparkle — and it also determines whether the pigment survives your process at all.

The size-to-effect map

Two caveats. First, the size band interacts with film thickness: a coarse grade in a thin film will protrude and create surface roughness. Second, size distribution width matters as much as the median — a wide distribution blends satin and sparkle and rarely gives a clean result.

Coatings: orientation is the whole game

• Loading: effect pigments sit at low percentages by weight of total formulation; exceeding the useful range adds cost and dullness rather than effect.
• Base coat: light bases dilute the effect, dark bases amplify it. Decide the base before you test the pigment.
• Film build: the effect coat must be thick enough to let plates align, thin enough to avoid trapping them mid-rotation.
• Solvent profile: slower, controlled evaporation improves alignment; too fast freezes plates at random angles.

Plastics: the process will punish you

In plastics the failure modes are mechanical rather than optical. Effect pigments are plate-like, and plates break under shear. Practical consequences:

• Masterbatch carrier: match the carrier resin to the final polymer to avoid dispersion defects and weld-line cosmetics.
• Shear history: high-shear compounding and small gates break flakes and dull the effect. Use low-shear screw configurations and generous gates.
• Weld lines and gates: plates align with flow, so weld lines almost always show as a visible line. Move gates or accept and design around it.
• Recyclate: regrind further breaks flakes — expect a progressive loss of sparkle over regrind cycles.