What Gouache Is: Opaque Watercolour for Layered Art

Gouache is an opaque water-based paint made with pigment and a binder, often with an added white pigment that gives it a matte, solid finish. Unlike transparent watercolour, it can cover the layers beneath it, making it useful for building colour, correcting shapes and creating crisp details.

That covering power is central to gouache’s appeal: artists can move from broad, flat areas to fine marks while keeping the surface visually unified. This guide explains what gouache is and how its opacity shapes the way artists work with it.

• 2 ways Gouache can be applied: transparently or opaquely, depending on the amount of water.
• 0 fixed ratios The supplied material specifies no water-to-paint ratio for achieving opacity.
• 0 stated drying-time figures The supplied material gives no universal drying time for gouache.

What is gouache paint?

Gouache is an opaque watercolour: it is worked with water, but unlike a transparent watercolour wash, it can cover paint beneath it. That makes it possible to place a lighter colour over a darker passage without the darker layer showing through.

How water changes gouache

The amount of water changes how gouache behaves: used with less water, it can form an opaque layer; thinned with more, it can create a more transparent passage. The same paint can therefore be used for both solid coverage and lighter, wash-like effects.

Opacity and transparency describe different ways of applying gouache, not fixed specifications for every paint. The supplied information gives no pigment ratios, drying times or product specifications, so those details should not be assumed to be the same across paints.

How does gouache differ from transparent watercolour?

Gouache differs from transparent watercolour in how much it covers: watercolour lets underlying layers show through, while gouache can hide them beneath a more even layer of colour.

Coverage

Transparent watercolour depends on the colour and marks beneath remaining visible; a transparent wash laid over a darker area allows that area to affect the result. Gouache can instead put a light colour over a dark layer with less of the dark showing through, making it useful when the intended finish calls for covered, even colour.

• Transparent watercolour: choose it when visible underlying colour is part of the result.
• Gouache: choose it when you want more coverage or to place a lighter layer over a darker one.

Water and transparency

Gouache remains water-based and can be diluted with water, so its opacity is not an absolute rule: the amount of water changes how transparently it is applied. The practical distinction is the intended result—visible underlying colour with transparent watercolour, or a more covering layer with gouache.

Why use gouache for layered painting and illustration?

Gouache suits layered painting and illustration because its opacity lets artists cover earlier colours, paint lighter highlights over dark passages and revise an area with another layer. Used like opaque watercolour, it retains water-based handling while allowing paint to conceal what lies beneath; the amount of water added can shift its use between more transparent and more opaque marks.

Gouache dries to a flat, velvety matt finish, which makes it useful for illustration and design work where an even field of colour is wanted. Unlike a transparent watercolour wash, an opaque gouache layer can mask the colour below, helping keep shapes and corrections visually clear.

Gouache and artwork prepared for scanning

Gouache can also suit artwork intended for scanning: its even, opaque surface avoids the uneven transparency of layered washes and produces a flat finish. For a practical test, paint a light colour over a dark layer and check whether the underlying colour remains hidden; then assess whether the dry surface looks evenly matt across the area.

When does gouache not behave as expected?

Water changes coverage

Gouache behaves unexpectedly when added water thins its coverage: the paint may let the colour beneath show through instead of hiding it. Gouache is not limited to solid, opaque blocks; the same paint can be handled more transparently or opaquely depending on how much water is added.

Overpainting is useful when a passage needs correction, but it covers earlier work and changes the visible surface. It is therefore different from a transparent wash, which allows underlying colour to remain visible.

Traditional and acrylic gouache

Traditional gouache is water-soluble, so reworking it with water can affect a dried passage. Acrylic gouache is a distinct option described as waterproof, making its behaviour different when later layers or other materials are applied.

• Traditional gouache: water can thin the paint and reduce opacity, exposing underlying colour.
• Acrylic gouache: waterproof once dry, so it does not behave like water-soluble traditional gouache when reworked with water.

How should an artist choose between gouache and acrylic gouache?

Choose traditional gouache when you want water-based handling, the option to rework paint, and control over transparency by adding water; choose acrylic gouache when you need a waterproof layer that dries matte and opaque. The key distinction is what happens after drying: traditional gouache can be worked with water, while acrylic gouache is suited to layers that should resist water.

• Traditional gouache: Choose it when you may want to soften or rework a passage, or shift between transparent and opaque effects by varying the water. Its opacity also lets you place lighter colours over darker paint.
• Acrylic gouache: Jackson’s Art’s gouache guide describes it for illustration, graphic design, animation cel painting and poster design. Its matte finish and flat, opaque colour suit these applications; its waterproof quality also makes it a different choice for mixed media when a water-resistant layer is needed.

For a painting that depends on adjustable washes and later water-based revisions, traditional gouache is the more suitable choice. For graphic work that calls for an even matte surface, flat opaque colour or a layer that can withstand water, acrylic gouache is the more suitable choice.

What should you test before starting a gouache painting?

Before starting a gouache painting, test how your chosen paint and water mixture cover a dark passage, how a lighter layer sits over it, and whether the finished surface suits your intended use. Gouache can work both transparently and opaquely, depending on how much water you add, so make two small swatches on your painting surface: one diluted and one more opaque. Compare how clearly each shows the layer beneath.

A correction test shows how readily you can paint over an area that appears dry. Brush a lighter colour across a dried-looking dark swatch and check whether it covers the underlayer or disturbs it. The available information does not establish a universal drying time, so judge the surface itself rather than relying on a fixed number of minutes.

Check the finish for scanning or design

For work intended for scanning or design, assess the swatches in the finished, dry state. Gouache dries to a matt surface and can provide flat, opaque colour; check whether that degree of opacity and finish gives the result you want, especially where a clean light-over-dark layer matters.

Frequently asked questions

Written byGideon Maberly

Gideon Maberly covers contemporary artists, movements and exhibitions across Asia-Pacific and the Americas. His editorial approach connects individual works to wider artistic conversations without losing sight of what visitors can see in the gallery.

Topic guide: Artists: The Complete Guide