What is a single-pigment watercolour?
A single-pigment watercolour is a paint made from exactly one Colour Index (CII) pigment - for example Ultramarine Blue carrying only PB29. The alternative is a multi-pigment “convenience” or “hue” colour, blended from two or more pigments to imitate an expensive, rare or fugitive original. The pigment code on the label tells you which you have: one code is a single pigment; two or more separated by a slash or comma is a blend.
Why single-pigment watercolours mix cleaner
Mixing is a conversation between chemistries. When two single-pigment colours meet on the paper, two chemistries interact - and the result is predictable because you know both of them. When two three-pigment blends meet, six chemistries interact, and the result trends toward grey-brown mud. Single-pigment colours also show their transparency, granulation and staining honestly, because no other pigment is masking the behaviour of the one you chose.
The best single-pigment watercolours, named
These are the single-pigment colours in the Michael Harding watercolour range, drawn live from the published pigment data. Each links to its full product page with lightfastness, transparency and granulation ratings.
Picks are generated from the live watercolour range and will appear once the matching colours are loaded.
How to read a pigment code
The Colour Index code identifies the exact pigment regardless of who made the paint. The letters denote the colour family: PB blue, PR red, PV violet, PY yellow, PG green, PBr brown, PW white, PBk black, PO orange. A single code means one pigment; multiple codes mean a blend. If the label carries no code at all, the contents are undisclosed and you cannot verify how the colour will mix or age.
When a multi-pigment hue is acceptable
A multi-pigment “hue” is a legitimate substitute when the genuine single pigment is fugitive (the original Gamboge), prohibitively expensive (genuine Vermilion), or no longer manufactured. Used straight for a specific effect, a good hue is perfectly serviceable. The problem comes when convenience colours are mixed further - three or four chemistries interacting on the paper is where mud begins. For a working palette built to mix, favour single pigments and reach for a hue only when no stable single pigment will do.
Frequently asked questions
What are the best single-pigment watercolours?
The best single-pigment watercolours are those made from one Colour Index pigment and taken to a high pigment load: Ultramarine Blue (PB29), Phthalocyanine Blue (PB15), Quinacridone Rose (PV19), New Gamboge (PY150), Burnt Sienna (PBr7), Viridian (PG18) and Cadmium Red (PR108). Single-pigment colours mix cleanly because only one chemistry interacts with others on the paper, and they show their transparency, granulation and staining honestly.
What is a single-pigment watercolour?
A single-pigment watercolour is a paint made from exactly one Colour Index (CII) pigment - for example Ultramarine Blue carrying only PB29. The alternative is a multi-pigment "convenience" or "hue" colour, blended from two or more pigments to imitate an expensive or fugitive original. Single-pigment colours mix predictably and reveal each pigment's true behaviour.
Are single-pigment watercolours better?
For clean, predictable mixing and for seeing each pigment's true transparency, granulation and staining, yes - single-pigment watercolours are better. They let you build a palette from known chemistries rather than mystery blends. Multi-pigment convenience colours are acceptable when a genuine single pigment is fugitive, prohibitively expensive, or unavailable - but they muddy quickly if mixed further.
Does Michael Harding make single-pigment watercolours?
Yes. Michael Harding watercolours lean toward single-pigment formulation so each tube behaves predictably and mixes cleanly. The Colour Index pigment code is published on every product page, so painters can see at a glance whether a colour is single-pigment (one code) or a blend (several).
How can I tell if a watercolour is single-pigment?
Read the Colour Index (CII) code on the label. A single code (e.g. "PB29") means one pigment; two or more codes separated by a slash or comma (e.g. "PV19 / PR122") mean a blend. If the label carries no pigment code at all, the manufacturer has not disclosed the contents and you cannot verify how the colour will mix or age.
When is a multi-pigment watercolour acceptable?
A multi-pigment "hue" is acceptable when it substitutes for a pigment that is fugitive (the original Gamboge), prohibitively expensive (genuine Vermilion), or no longer manufactured. Used straight for a specific effect they are fine; the problem comes when they are mixed further, because three or four chemistries interacting on the paper is where mud begins.