Color streaks and pigment dosing
Coloring pellets is a very common topic. The two recurring problems are transparent streaks (uneven color) and getting a homogeneous color at a low pigment percentage.
What goes wrong
Section titled “What goes wrong”- Pigment percentage too high is a real failure mode, not just a waste: too much pigment changes the melt viscosity and shows up as defects.
- Solid masterbatch must be dosed at at least ~2% of the final material to get a homogeneous output; below that you get uneven color. The exact figure depends on the masterbatch quality, and it also slightly changes the material viscosity.
- Transparent streaks happen when solid masterbatch granules are too large to disperse evenly. Grinding the masterbatch finer lets a lower percentage disperse without leaving clear streaks.
- With Liquid Masterbatch, dosing is easier and more even, but purging between colours still matters — residual pigment takes a long purge to clear.
Guidance
Section titled “Guidance”| Symptom | Likely cause | Action |
|---|---|---|
| Transparent / clear streaks in colored parts | Solid masterbatch granules too large, or % too low | Grind the masterbatch finer; ensure ≥ ~2% dosing |
| Color washes out / inconsistent | Dosing below the homogeneity threshold | Increase toward ~2%+ (solid), verify mixing |
| Viscosity/flow changed after coloring | Pigment % too high | Reduce pigment %; re-check flow (Rotation Volume) |
| Old color bleeding into new | Insufficient purge at color change | Purge until clean — see Material change and purge |