Benzimidazolone Brown (Pbr25)

August 1, 2025

Benzimidazolone Brown is a very popular ingredient in many mixed paints, but as a standalone pigment in watercolor, it is not as commonly used. This is a bit unfortunate because it’s a very pleasant color with several advantages specifically as a watercolor pigment. The color is an intensely dark reddish brown, it moves very freely on wet paper, and it is transparent and dries completely smooth. Benzimidazolone Brown is fairly staining and very durable, though it loses quite a bit of value and hue as it dries.

The pigment was invented in 1960, making it a relatively modern colorant. It is an AZO pigment belonging to the Benzimidazolone pigment family, which includes everything from lemon yellows like PY175, to reds — such as PR175 — and everything in between. Even some reddish browns like Benzimidazolone Brown are part of this large pigment family.

The color is a relatively cool dark reddish brown, like a reddish burnt umber. This reddish hue makes it a bit tricky to find a good complementary color for neutral mixtures.

French Ultramarine is a color I often use with a brown to create neutral mixes, but it doesn’t work at all here — the result becomes far too violet. Even the cooler Phthalo Blue (RS) doesn’t work well; the mixture still turns out a bit violet. You need to use a more greenish blue to find a good complementary color. A color that works well is Phthalo Blue (GS), but even better is Phthalo Turquoise (PB16).

Benzimidazolone Brown + French Ultramarine

Benzimidazolone Brown + Phthalo Blue (RS)

Benzimidazolone Brown + Phthalo Turquoise

Benzimidazolone Brown can be seen as an intense and transparent version of English Red, at least when well diluted. It is sometimes recommended as a skin tone when highly diluted, but I find it a bit too pink for that purpose. However, it works very well as a value-reducer in various green color mixes. In a predominantly green landscape, this color is a great asset for creating various dark green mixtures.

PBr25 is a pigment well-suited for creating textures and patterns using cloth, sand, or salt; it readily forms patterns when such materials are applied to a wet surface.

This property is shared with its relative Benzimidazolone Red (PR175).

Not many pigments produce such distinct patterns when salt is sprinkled over a freshly painted surface.

The color also has a tendency to become glossy in darkly painted areas.

When light hits the surface at the right angle, on an area painted dark with Benzimidazolone Brown, you can see how glossy the surface becomes.

The pigment is excellent for mixing with all kinds of other colors. It’s no surprise that most manufacturers primarily use it as an ingredient in mixed colors. According to artistpigments.org, there are 59 mixed colors from various manufacturers that contain PBr25, while only 25 colors contain the pure pigment. So, the vast majority of all colors that include PBr25 are blends with other pigments.

Of those 25 unmixed colors, only 5 are labeled as Benzimidazolone or Imidazolone. All the others use a fantasy name for it. Common names include Red Brown or Permanent Brown. If you are interested in buying this color, check the pigment — it should be PBr25. The names given by manufacturers are often misleading.

benzimidazolone_brown_1 — Intensely reddish brown and transparent.

Large difference between wet and dry appearance. The color mainly loses its reddish hue as it dries, along with some value.

Information

Color Index Name: PBr25
Lightfastness: Very good
Transparency: Transparent – Semi-transparent
Staining: Medium staining
Granulation: None