What is watercolour granulation?

Granulation is a textured, speckled effect caused by heavy pigment particles settling into the valleys of watercolour paper. Some pigments (like Ultramarine and Cerulean) granulate naturally, while others (like Phthalo Blue) produce smooth, flat washes. It is a desirable effect for creating atmosphere and texture.

Which pigments granulate the most?

The strongest granulating pigments are heavy mineral colours: Ultramarine Blue (PB29), Viridian (PG18), Cobalt Blue (PB28) and Cerulean Blue (PB35), plus specialist granulators such as Potter’s Pink (PR233) and Cobalt Blue Deep (PB73/PB74). Mineral-based pigments granulate more than synthetic organics because their particles are heavier and larger. Note that “Manganese Blue Hue” is usually phthalocyanine (PB15) standing in for the discontinued genuine Manganese Blue (PB33) — its granulation is mild and varies by brand, so treat it as a smooth staining colour rather than a strong granulator.

How can I control granulation?

To increase granulation: use rough paper, more water, and let washes dry undisturbed. To decrease: use hot-pressed (smooth) paper, less water, and mix with non-granulating pigments. Granulation medium can be added to any colour to enhance the effect.

Granulation Chart Calculator — Free Watercolour Tool

How We Calculate This

Granulation Score

Each pigment has a base granulation score (1–10). These base scores map the published Handprint granulation ratings (Bruce MacEvoy's 0–4 "Gr" scale at handprint.com) onto a 1–10 range, so heavy mineral pigments such as Ultramarine (PB29), Viridian (PG18) and Cobalt (PB28) sit high, while smooth synthetic stains such as Phthalo Blue (PB15) sit at the bottom. The base score is then modified by paper texture, water ratio and technique to give a final predicted score.

Modifiers

Rough paper and wet techniques increase the score; smooth (hot-pressed) paper and dry brush decrease it. The modifier model is an indicative studio heuristic rather than a measured value — real granulation also depends on factors this tool does not capture.

Water hardness

Water hardness is a significant, well-documented factor: hard tap water (high in calcium and magnesium) produces noticeably more pronounced granulation than soft or distilled water, which gives smoother washes. If you want to maximise granulation and your water is soft, a granulation medium has a similar effect; if you want flat washes, distilled water helps. Granulation strength also varies between brands of the same pigment, so treat scores as a guide and test-swatch your own paints.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Always verify quantities before purchasing materials.