Blue Watercolour Swatches

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Blue Swatches

the swatch library

PB15: Phthalocyanine Blue Pigments

the Pb15 pigments

Phthalocyanine Blue is a family of vibrant blue shades under the bracket PB15, with a wide spectrum of shades from green-blues (PB15:3), mid-blues (PB15:1), to red-blues (PB15:6). These synthetic blue pigments share some key characteristics; they are all lightfast, transparent and strongly-staining. Phthalocyanine is often abbreviated to Pthalo (pronounced ‘Thalo’).

I use Pthalo Blue GS as my primary cyan, as part of my modern primaries. Its transparent nature is perfect for glazing techniques and can appear luminous on paper. However, be cautious—it’s a very staining pigment, which means it absorbs into paper quickly, making corrections and lifting difficult. It also has strong tinting strength, meaning it strongly influences the final colour when mixed with other pigments. Pthalos do generally experience a large drying shift; as they dry, they lighten, and will lose some saturation. This drying shift is more visible with the redder-blue pigments, which lighten considerably more when dry.1

PB15 and PB15:3 is often used as a substitute for Manganese Blue (PB33) or Cerulean Blue (PB35), which are marketed as “Hues”. This is because both genuine Manganese and Cerulean Blue are known to be toxic, and expensive. Their production can also have environmental impacts.

Genuine Cerulean Blue also has a weak tinting strength, and is strongly granulating. Cerulean Blue Hue offers a much cheaper alternative that can be adjusted to be non-granulating, and has a stronger tinting strength, making it more prominent in colour mixes.

PB26: Cobalt Blue

A soft, light blue with a good tinting strength. It’s expensive, but artists value it’s permanence and muted tone.

PB27: Prussian Blue

A dark, rich blue pigment, which is both transparent and reasonably lightfast.

PB28: Cobalt Blue

PB29: Ultramarine Blue

A classic deep blue pigment, derived from Lapis Lazuli, traditionally from Afghanistan. It has a good lightfastness, and mixes well with other colours.

PB33: Manganese Blue

PB15:3 is at the redder end of the Pthalo Blue spectrum. It’s often used to achieve deeper, more violet-leaning tones.

PB35: Cerulean Blue

A light, sky-blue pigment that is opaque and strongly granulating. Ideal for painting skies and water. Toxic and expensive.

Pb36: Cobalt Teal Blue & Cerulean Blue Chromium

An opaque muted green-blue pigment, which mixes well with other colours.

Similar to genuine Cerulean blue, but is more lightfast.

PB37: Cerulean Blue Deep

A deeper, more intense version of Cerulean Blue, used to create darker blue tones.

Pb60: Indanthrone Blue & Maya Blue

PB15:3 is at the redder end of the Pthalo Blue spectrum. It’s often used to achieve deeper, more violet-leaning tones.

A historical pigment made from indigo and palygorskite clay. Known for its colour stability and durability.


Mixed Blues

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