The basic difference
Transparent watercolor lets light pass through the pigment layer, reflect off the white paper beneath and travel back to your eye. That gives the glowing quality watercolor is known for. Opaque watercolor contains pigment that blocks more light, so it covers what is underneath and looks more solid and flat.
Most pigments sit on a spectrum, so it helps to think of colors as transparent, semi-transparent, semi-opaque or opaque rather than two strict groups.
How to tell which is which
- Check the label. Many manufacturers print a transparency symbol or rating on the tube or pan. Symbols differ between brands, so check each brand’s key.
- Do a test strip. Draw a thick black line with a waterproof marker on watercolor paper. Paint a swatch of your color across it. If the line shows through, the color is transparent; if it is hidden, the color is opaque.
- Look at the paint. Transparent colors often look darker or less creamy in the pan than they appear on paper, while opaque colors can look creamy and solid right away.
Opacity is largely a property of the pigment, so the same pigment tends to behave similarly across brands. It can also change with how thickly you apply it.
Layering and mixing behavior
Transparent colors suit glazing: a dried layer is overlaid with another thin layer, and the colors combine optically. Opaque colors cover earlier layers, and heavy over-layering can look chalky or dull. Mixing many opaque pigments, or mixing opaque with transparent ones, can also give flatter, less luminous results (see mixing colors in watercolor). Our article on transparent watercolor painting, layering and glazing shows the method in detail.
When to choose each
- Transparent: luminous washes, glazing, skies, water, flowers, soft color transitions.
- Opaque: covering mistakes, adding light details over darker areas, solid color, earthy tones with a chalky quality.
Many painters use mostly transparent colors with a few opaque ones for specific jobs.
Opaque watercolor vs gouache
Gouache is also water-based, but is formulated to be opaque, often with added chalk or similar filler. It can be reactivated with water, like watercolor, and is often painted from dark to light. Opaque watercolor pigments are watercolor paints that happen to cover well, but they are still usually used in thinner, more watery applications than gouache. The two can be combined, and some artists add a little opaque paint to a watercolor painting for final highlights.
The “golden rule” of watercolor
People often cite the rule that you work from light to dark, keeping the white of the paper for your lightest areas. This works best with transparent colors, since light areas are protected rather than painted over. It is a guideline, not a law, and opaque colors are one way artists break it.
FAQ
What is transparent watercolor? Paint whose pigment lets light through to the paper so layers glow and combine.
What color does opaque look like? It looks solid and flat, covering what is underneath.
Is opaque watercolor the same as gouache? No, though they overlap in use.
Choosing paints is part of building a kit; see watercolor supplies for beginners.