The basic order: thin to thick
A common way to build an acrylic painting is to start with thin, dilute paint and finish with thicker, more opaque paint. The first layers map out composition, shapes and values. Later layers add color variety, edges and details. Many painters also work from the background forward, painting distant areas such as sky first, then mid-ground, then foreground details.
Acrylic has no strict rule like oil painting’s “fat over lean”, but starting thin and finishing thick keeps the surface manageable and helps avoid a heavy, overworked look. It also helps to use a primed surface; see whether acrylic is good on canvas for priming basics.
Underpainting
Should you do an underpainting with acrylic? You do not have to, but many painters find it useful. An underpainting is a first layer that sets values and a base color scheme. Options include:
- Toned ground (imprimatura). A thin wash of a single color, such as a warm earth tone, over the whole surface to unify the colors and remove the white of the canvas. The idea is explained in toning a canvas for oil painting, and it works the same way here.
- Monochrome underpainting. Light and dark shapes blocked in with one color, so you settle values before worrying about color.
- Complementary underpainting. A color that contrasts with the final colors in an area, which can show through and add vibrancy. A warm red tone beneath greens is one example.
Keep it thin and let it dry before you continue.
How long to wait between layers
How long does a layer of acrylic take to dry? It depends on thickness, humidity, temperature, the paint brand and the surface. Thin layers often feel dry to the touch within minutes, while thick layers can take hours or longer, and may feel dry on top while still soft beneath. A practical test is to touch a hidden edge gently; if it feels cool or tacky, wait longer. A hairdryer on a low setting can speed things up, though going too hot or too close may cause problems on thick paint.
Painting over a layer that is still wet makes the colors mix, which is useful for blending but can lead to mud or lifting when you did not intend it. If you want crisp edges or clean glazes, wait until the layer is fully dry.
Glazing
A glaze is a thin, transparent layer of color over a dry layer. It shifts the color underneath without hiding it, giving depth that is hard to get by mixing alone.
- Make sure the paint below is completely dry.
- Mix a small amount of paint with a glazing medium or a clear acrylic medium. Using only water can make the glaze weak; a medium keeps the film stronger. Follow the product directions.
- Brush it on with a soft brush in smooth, even strokes and avoid going back over areas that are starting to dry.
- Let it dry, then add another glaze if needed.
Transparent pigments tend to glaze best, but check the label for opacity ratings.
Opaque layers, scumbling and dry brushing
Once the base is established, use thicker paint for opaque coverage. Two techniques add variety:
- Scumbling: a thin, broken layer of lighter or opaque paint dragged over a dry layer so some of the color below shows.
- Dry brushing: a nearly dry brush with little paint, dragged lightly across the surface to catch on texture. It is helpful for grass, bark, clouds and highlights.
Thick paint applied with a palette knife or stiff brush (impasto) is usually left for the final stages. For brush choices, see brush types for acrylic painting.
Is it okay to paint over acrylic?
Yes. Dry acrylic can be painted over, and many painters rework passages or change a whole painting this way. For best results:
- Make sure the old paint is dry and clean.
- If the surface is glossy, you may need to lightly sand it or apply a coat of gesso to improve grip.
- Cover dark areas with several thin opaque layers, or a coat of white gesso first, rather than one thick coat.
- If the painting has been varnished, check the varnish maker’s guidance, as you may need to remove it first.
Problems and fixes
- Muddy colors: Too much mixing or painting into half-dry layers. Let layers dry, and keep mixes to a few colors.
- Streaks: Paint partly dried while being brushed. Work faster, add a little medium, or use thinner coats.
- Lifting or peeling: The brush disturbs the layer below because it was not fully dry. Wait longer.
- Cracking: Often from very thick paint or very diluted layers. Keep dilution modest and let thick paint cure.
A simple layering exercise
Try a small landscape: tone a canvas panel with a light wash, block in sky and land in thin paint, let it dry, add a mid-tone layer, glaze one area for atmosphere, then finish with a few opaque details. For deciding when to stop, see how to finish a painting. For other starter habits, see acrylic painting tips for beginners.