Color streaks and pigment dosing
Status v0 — drafted from customer-chat evidence, pending human review.
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 the chats show
Section titled “What the chats show”- Pigment percentage too high is a real failure mode: “probabilmente è troppo alta la % di pigmento nel masterbatch.” Too much pigment can change the melt viscosity and cause 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. A customer workaround: grind the masterbatch smaller so a lower percentage disperses without leaving clear streaks.
- With liquid pigment / Liquid Masterbatch, dosing is easier and more even, but purging between colors still matters: one customer had to purge a lot to clear residual pigment when switching.
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 |