Masterbatch Loading Ratio FAQ: How Much Should You Add?

Getting the Dosage Right

The loading ratio — how much masterbatch you add to your base polymer — is the single most practical decision in plastic coloring. Add too little and color is weak; add too much and you waste money and risk defects. This FAQ answers the most common questions about loading ratios.

What is a loading ratio?

The loading ratio (also called let-down ratio or addition rate) is the proportion of masterbatch added to base resin, expressed as a percentage (e.g., 2%) or a ratio (e.g., 1:50).

What is a typical loading ratio?

Most color masterbatch is used at 0.5%–5%. Black and white masterbatch are commonly 1–3%, while special-effect and some additive masterbatches may be higher or lower.

How do I calculate the final pigment concentration?

Use the formula: Final % = (Masterbatch loading % × Masterbatch pigment %) / 100. For example, a 40% carbon black masterbatch at 2% gives 0.8% carbon black in the finished part.

Why does my color look weak?

Weak color usually means the loading ratio is too low, or the masterbatch pigment concentration is insufficient. Check that your dosing equipment is accurate and that the masterbatch matches your target ratio.

Can I use the same ratio for all resins?

No. Different polymers have different opacity and pigment affinity. A ratio optimized for PP may not work for ABS or PET. Always validate the ratio in your specific resin.

What happens if I add too much masterbatch?

Over-dosing wastes pigment, increases cost, and can cause streaks, screw slip, and even pigment migration. It can also alter mechanical properties by introducing excess carrier resin.

Should I dose by weight or volume?

Always dose by weight. Masterbatch density differs from the base resin, so volumetric dosing introduces ratio errors. Gravimetric dosing (±0.1%) is preferred for critical colors.

How do I verify my dosing is accurate?

Periodically weigh a known volume of output, or use a gravimetric feeder with continuous weight feedback. Regular color measurement (Delta E) confirms consistent dosing.

Can a higher-concentration masterbatch save me money?

Often yes. A 50% pigment masterbatch requires half the loading of a 25% version to reach the same final concentration, reducing carrier cost and dosing volume — but confirm dispersion quality at the higher concentration.

Conclusion

The correct loading ratio balances color specification against cost and process behavior. MHK Color formulates every masterbatch to a target let-down ratio and helps customers validate it in their equipment. Provide your base resin and target color, and we will recommend the optimal masterbatch and loading ratio.