Phthalocyanine Blue is a single chemical (copper phthalocyanine) that exists in multiple crystal forms, each with subtly different shade and dispersion behavior. Choosing the wrong crystal form gives you a blue that looks slightly off or flocculates in your system. PB15:1, PB15:3, and PB15:4 are the three you'll encounter most.
PB15:1 — Alpha crystal form
Shade: Slightly reddish blue. Warmer than PB15:3.
Stability: Alpha crystal form is metastable — converts to beta under heat or solvent influence. Stabilized PB15:1 grades resist this conversion.
Heat stability: 300°C+ when stabilized.
Lightfastness: Blue Wool 8/8.
Best for: Plastics (especially PVC and rubber compounding where the slightly warmer shade matches existing color targets), some printing inks, some paints. Less common than PB15:3.
PB15:3 — Beta crystal form (industry standard)
Shade: Greenish blue. The reference shade for "phthalocyanine blue" globally.
Stability: Beta is the thermodynamically stable form — won't change under processing.
Heat stability: 300°C+.
Lightfastness: Blue Wool 8/8.
Application range: The widest. Used in process cyan inks (offset, flexo, gravure), architectural paints, automotive coatings, plastic masterbatch (PVC, HDPE, PP, PET, ABS), powder coatings, textile printing, rubber, construction.
Best for: Default choice for blue in 95% of applications unless you have a specific reason to use PB15:1 (slightly warmer shade) or PB15:4 (waterborne paint stability).
PB15:4 — Non-flocculating beta crystal form
Shade: Greenish blue, similar to PB15:3.
Differentiator: Surface-treated to prevent flocculation in waterborne systems and high-shear mixed coatings. Standard PB15:3 can flocculate (re-aggregate) in waterborne emulsions or when sheared, causing shade shift. PB15:4 doesn't.
Heat stability: 300°C+.
Lightfastness: Blue Wool 8/8.
Best for: Premium waterborne coatings, automotive basecoat (where flocculation under high-shear pumping is a real risk), high-end architectural paint where shade stability through shelf life matters most. More expensive than PB15:3 but worth it for these applications.
Quick selection guide
| Application | Recommended Grade |
|---|---|
| Process cyan offset ink (CMYK) | PB15:3 |
| Process cyan gravure / flexo ink | PB15:3 or flushed PB15:3 |
| Architectural waterborne paint | PB15:4 (premium) or PB15:3 (standard) |
| Architectural solvent-borne paint | PB15:3 |
| Automotive basecoat (waterborne or solvent) | PB15:4 (non-flocculating) |
| PVC pipe and profile | PB15:1 (warmer shade) or PB15:3 |
| HDPE / PP masterbatch | PB15:3 |
| Engineering plastics (PET, ABS, PC) | PB15:3 or PB15:1 stabilized |
| Rubber compounding | PB15:1 |
| Textile printing | PB15:3 |
| Powder coating | PB15:3 (ultra-fine grade) |
| Construction (cement, paving) | PB15:3 (alkali-stable) |
Other phthalocyanine blue forms (less common)
PB15 (no suffix): Unstabilized blue, mostly historic.
PB15:2: Surface-treated alpha — non-crystallizing alpha for solvent-borne systems where alpha is desired.
PB15:6: Epsilon crystal form — very reddish blue, niche use in inks and special-effect coatings.
PB16: Metal-free phthalocyanine, used where copper-free formulations are required (rare).
Practical notes for buyers
When ordering, always specify both the CI code (PB15:3) AND the application — the same CI code can be supplied with different surface treatments optimized for different binder systems. "PB15:3 for waterborne acrylic" and "PB15:3 for solvent-borne alkyd" may have different surface treatments.
Always request a free 50-100g evaluation sample before bulk qualification. Test in your actual binder/polymer system, not a generalized lab dispersion. The right surface treatment for your binder will dramatically out-perform a generic version.
Kanani Pigment & Paste supplies PB15:1, PB15:3, and PB15:4 in multiple surface-treated variants for different application classes. Contact our technical sales team with your binder system and we'll recommend the right variant.
Need help applying this to your specific application?
Our technical sales team works directly with formulators every day. Free 50-100g samples shipped within 2-3 business days.