04 — FAQ
Frequently Asked Questions
Quick answers to common questions about organic pigments — from sample qualification to lightfastness ratings
Get straight answers to the most frequently asked technical questions about organic pigments. Whether you’re qualifying a new pigment sample, interpreting lightfastness and weatherfastness ratings, comparing pigment chemistry families, or troubleshooting a formulation issue, this section covers the practical knowledge formulators and buyers need every day.
Coating Pigments FAQ
What’s the best blue pigment for exterior architectural coatings?
PB15:3 (Phthalocyanine Blue, beta crystal). It delivers Blue Wool Scale Grade 8 lightfastness — 10+ year outdoor durability. The beta crystal form offers better flocculation resistance than alpha (PB15:1). For water-based architectural coatings, choose a surface-treated grade for faster wetting and lower foam. Typical loading: 3–8% in full-shade formulations.
Why does my red coating fade faster than my blue?
Red pigments generally have lower inherent lightfastness than phthalocyanine blues. PB15:3 blue is naturally Grade 8. Common reds range from Grade 5 (BONA lakes, PR57:1) to Grade 7–8 (Quinacridone PR122, DPP PR254). If you’re using a monoazo red (PR3, PR112) outdoors, expect 1–2 years before visible fading. Upgrade to PR122 (quinacridone magenta) or PR254 (DPP red) for exterior durability.
Can I use the same pigment for solvent-based and water-based coatings?
Not always. Pigment surface treatment matters. Phthalocyanine pigments work in both — but water-based systems benefit from surface-treated grades for faster wetting and lower foam. Azo pigments may require different dispersants in aqueous vs. solvent systems. Best practice: request a water-compatible grade if your system is aqueous; the supplier should confirm compatibility on the TDS.
What causes pigment flooding/floating in my coating?
Pigment separation during drying. When two or more pigments have very different particle sizes, densities, or surface treatments, convection currents in the drying film separate them. Fix: use pigments with similar particle size, add anti-floating dispersants, or increase low-shear viscosity. Some pigment pairs are inherently incompatible — pre-test combinations.
Ink Pigments FAQ
What pigments should I use for CMYK offset printing?
The standard set: PY12 or PY13 (Yellow), PR57:1 (Magenta), PB15:3 (Cyan), and Carbon Black (Key). These deliver the transparency, water balance, and rheology required for offset lithography. PR57:1 provides the clean magenta tone needed for process color. For higher-end work (magazine, art book), some formulators use PR122 (quinacridone) for magenta — better lightfastness but higher cost.
How do flexo pigments differ from offset pigments?
Flexo inks are low-viscosity liquids; offset inks are high-viscosity pastes. Flexo requires pigments that disperse easily in low-viscosity vehicles and release solvent quickly during drying. Typical flexo pigments: PY14, PY83 (yellow), PR48:2 (magenta), PB15:3 (cyan). Offset uses PY12/13, PR57:1, PB15:3 — designed for paste rheology and fountain solution interaction.
What pigment properties matter most for inkjet inks?
Particle size and distribution. Inkjet nozzles are 20–50 µm; pigment particles must be <200 nm with D90 <300 nm to avoid clogging. Narrow particle size distribution (PSD) is more important than average size. Also critical: dispersion stability (no settling during storage) and low ionic content (to prevent nozzle corrosion).
Plastic Pigments FAQ
What causes white powder on my plastic part surface?
Pigment blooming — migration to the surface. The pigment has partially dissolved in the polymer and migrated out during cooling. Most common with low-molecular-weight pigments (monoazo, some disazo) in flexible PVC or polyolefins. Fix: switch to high-MW pigments (Phthalocyanine, Quinacridone, DPP) or reduce pigment loading below solubility limit.
Which pigments survive PA (nylon) processing at 280°C+?
Phthalocyanines (PB15:3, PG7), Quinacridones (PV19, PR122), and DPPs (PR254). These families remain stable at 300–350°C. Benzimidazolones (PY151, PO36) can handle up to 300°C in selected formulations. Avoid monoazo pigments — they degrade above 220°C, causing shade drift and mold deposit.
How do I prevent warpage in PP with organic pigments?
Organic pigments can nucleate PP crystallization, causing differential shrinkage (warpage). Phthalocyanine blues and greens are among the strongest nucleating agents and cause the most warpage. Solutions: use low-nucleation grades, blend with inorganic pigments to dilute nucleation, or use specifically formulated low-warpage organic pigment grades.
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