Watercolor and Gouache

Watercolor and gouache are water-based paints bound in gum arabic, distinguished by watercolor's transparency and gouache's opacity from added white or higher pigment load.

Definition

Painting media in which pigments are bound in a water-soluble gum, used transparently as watercolor — where the white of the paper provides the lights — or opaquely as gouache, which can cover underlying layers.

Scope

This topic covers the materials and methods of water-based painting: transparent watercolor worked in washes and glazes on white paper, and opaque gouache (body color) capable of flat, covering passages, including techniques such as wet-in-wet, wet-on-dry, lifting, and the reliance on the paper's whiteness for lights.

Core questions

• How does the binder and pigment load distinguish transparent watercolor from opaque gouache?
• Why does transparent watercolor rely on the white of the paper rather than white paint for its lights?
• What techniques — wet-in-wet, wet-on-dry, lifting, drybrush — define watercolor handling?
• How do the spontaneity and limited reworking of watercolor shape its expressive character?

Key concepts

• Gum arabic binder
• Transparent wash
• Wet-in-wet and wet-on-dry
• Lifting and reserving whites
• Body color (gouache)
• Drybrush

Key theories

Transparency and the white of the paper

The principle that in pure watercolor the lightest values come from the unpainted white paper showing through transparent washes, requiring the artist to work from light to dark and reserve highlights in advance.

Opacity of gouache

The understanding that gouache, made opaque by added white or a high pigment-to-binder ratio, allows flat covering layers and overpainting of lights onto darks, distinguishing it from transparent watercolor.

History

Water-based pigments have ancient roots in manuscript illumination and East Asian ink-and-color painting. Transparent watercolor developed as an independent fine-art medium in Britain in the eighteenth and nineteenth centuries, reaching new heights with J. M. W. Turner, while gouache and body color served illustration, design, and topographical work. The medium remained central to sketching, botanical and natural-history illustration, and plein-air practice.

Debates

Watercolor as a major or minor medium

Watercolor was long regarded in some European academies as a lesser, preparatory medium compared with oil; its champions argued that its transparency and immediacy make it a fully expressive fine-art medium in its own right.

Key figures

• J. M. W. Turner
• John Singer Sargent
• Albrecht Durer

Seminal works

• mayer1991
• gottsegen2006
• wilcox2000

Frequently asked questions

What is the difference between watercolor and gouache?

Both are bound in gum arabic, but watercolor is used transparently so the white paper shows through, while gouache is opaque — owing to added white or a higher pigment load — and can cover layers beneath it.

Why are highlights left as bare paper in watercolor?

Because transparent watercolor has no opaque white, the brightest lights are usually created by leaving the white of the paper unpainted, so artists plan and reserve those areas from the start.