Why Do Pearl-Color Plastic Parts Show Flow Marks?

Pearl-colored plastic parts often show flow marks (flow lines) because of how the pearl pigment works. The pigment is heavier and thicker than normal colors, so it doesn't mix as evenly when the plastic flows.

Where Do Flow Marks Usually Appear?

1. Weld Lines (Molding Lines) – When melted plastic flows from two directions and meets, the pearl pigment can clump there, making a visible line. Please see the picture below.

2. Near the Injection Point (Gate) – The high pressure at the gate can push the pigment unevenly, causing streaks or marks.

Are Flow Marks Normal?

Yes, flow marks are common with pearl colors and are usually acceptable in the industry. However, it's best to check with your customer to make sure they're okay with them.

If flow marks are a problem, another option is pearl-color overspray (painting the part after molding). This avoids flow marks but costs more.

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