PY 151 – benzimidazolone yellow H4G

It is used as a replacement for cadmium yellow

Manufacturer/ product code:  Kremer / 23300
Chemical Description:  organic monoazo pigment, benzimidazolone
Color: yellow
Color Index: PY 151
Date:  from 1971

PY 151 – Benzimidazolone Yellow H4G is a synthetic organic pigment belonging to the benzimidazolone family, a class of high-performance yellow pigments known for their bright, warm hues, excellent lightfastness, and chemical stability. PY 151 is characterized by a clear, slightly reddish yellow with strong chromatic purity, making it highly versatile for both artistic and industrial applications.

Chemically, PY 151 is based on a fused aromatic benzimidazolone structure, in which nitrogen atoms stabilize the chromophore and provide exceptional resistance to light, heat, and chemical agents. This molecular robustness ensures excellent permanence in paints, coatings, inks, plastics, and fine art media. Its chemical inertness minimizes interactions with other pigments or binders, preserving color integrity over time.

In artistic applications, Benzimidazolone Yellow H4G exhibits high tinting strength and semi-opaque to opaque behavior depending on particle size and formulation. It mixes cleanly with other yellows, reds, and whites to produce a wide spectrum of warm tones, from bright golden yellows to muted oranges and pastels. Its transparency also allows for glazing and layering techniques in oil, acrylic, and watercolor painting, offering nuanced color modulation and depth.

From a conservation standpoint, PY 151 is highly stable and resistant to fading, maintaining both chromatic purity and brightness over extended periods. Its reliable chemical behavior ensures minimal degradation even in complex pigment mixtures.