Worth knowing up front what is in the tube. Holbein makes Cobalt Blue from a single pigment, PB15:3, listed as Copper Phthalocyanine, so this is a phthalo standing in for the cobalt hue rather than genuine cobalt. What you get is a clean, strong mid-blue: hue 3.0PB, value 3.5, chroma 10.5. Being single-pigment it mixes very predictably, and phthalo blue is a notably powerful tinter, so it travels a long way.

The hue is the useful thing here. At 3.0PB it is cooler and more neutral than an ultramarine without swinging as green as a turquoise, which makes it the blue to reach for when you want blue to read simply as blue. Skies, denim, ceramics, flat graphic shapes, and any palette where the blue must not look violet. It tints through a whole ladder of light blues with white, and because there is only one pigment behind it those tints stay clean instead of going grey. Steady three-star lightfastness.

What Makes This Colour Special

Pigment, lightfastness and series as published by Holbein. Holbein does not publish an opacity rating for individual colours; the range as a whole is described by Holbein as opaque.

Acrylic Gouache, Not Traditional Gouache

If you have not used the range before, acrylic gouache is a hybrid: the flat matte character of gouache with an acrylic binder underneath. Holbein Acrylic Gouache dries to a matte opaque finish and is water resistant once dry, so it does not reactivate with water like traditional gouache. Holbein lists it as suitable for paper, canvas, cloth, stone, wood, leather, plexiglass and concrete, which is a wider brief than most gouache can manage. There is more about the maker on our Holbein page.

Why Holbein Acrylic Gouache Is in Serious Studios

• Genuinely opaque. Holbein describes the range simply as an opaque acrylic paint. It covers, including over darker colour, which is the whole point of reaching for gouache rather than watercolour.
• Velvety matte, no sheen. Holbein describes the colour as opaque, intense, smooth and velvety. It dries flat, which is why it photographs and scans without glare.
• Water resistant once dry, so you can layer. Holbein’s own wording, and the reason the range exists. A dry layer will take another one over the top without lifting.
• The colour you mix is the colour you get. Holbein states it does not shift in colour tone from wet to dried colour. Anyone who has watched a perfect grey dry into a different grey will appreciate that.
• Built to use straight from the tube. Holbein says it is specifically designed to be used directly from the tube and will dry to even, uniform paint layers.
• Works on more than paper. Holbein lists paper, canvas, cloth, stone, wood, leather, plexiglass and concrete, with excellent adhesion, and full compatibility with all acrylic mediums.

Getting the Most Out of This Tube

Straight from the tube is the default. This is what Holbein designed it for, and it is where you get those even, flat, uniform layers. Add a little water to loosen it, but go easy: very diluted washes can dry streaky across a large flat area, so build coverage in thin even coats rather than flooding it on.

Watch the palette, not the clock. Holbein gives an open time of roughly 10 to 30 minutes and notes the drying time is much like ordinary watercolour. The practical consequence is that paint left sitting on the palette will go off and will not come back, so squeeze out small amounts as you need them.

It plays well with acrylic mediums. Holbein states the range is compatible with all acrylic mediums, so you can change the body or extend the working time if you want to. Soft synthetic brushes suit it, since they hold enough paint to lay a flat area without dragging.

Questions About Holbein Cobalt Blue