Opacity, transparency and glazing: mixing on the palette versus mixing on the canvas
Opaque, semi-transparent, transparent
Opaque pigments scatter light back from the surface: Titanium White, the cadmiums, Mars colors, Cerulean, Naples Yellow. They cover whatever is under them and lighten a mix strongly. Transparent pigments let light pass through to the ground and back: Ultramarine, the phthalos, Alizarin and the quinacridones, Dioxazine, Raw Sienna, Indian Yellow, most lakes. They darken a mix and glow when thin. Semi-transparent is most of the rest: the umbers, Burnt Sienna, Viridian, Yellow Ochre, Ivory Black.
The tube usually marks it with a square: filled, half-filled or empty. The tube label guide explains the rest of the small print.
How opacity changes a mix
- A dab of an opaque pigment makes a transparent mixture opaque almost at once; the reverse takes a lot of transparent paint.
- Opaque mixes lighten and cool (because they scatter); transparent mixes darken and warm (because light travels further through pigment). Two paints of equal value mixed 1 : 1 will come out darker if both are transparent.
- Transparent darks (Ultramarine + Alizarin, Phthalo + Burnt Sienna) have depth; opaque darks (anything with Mars Black) look flat.
This is one reason painted mixes often come out darker than a simple color calculation predicts — and why the PaintMixLab engine models scattering as well as absorption for each pigment, and adds white in its standard recipes to land on the value you asked for.
Navy BlueRecipe by paint setMaroonRecipe by paint setForest GreenRecipe by paint setCharcoal GreyRecipe by paint set
Glazing: mixing with light
A glaze is a thin, transparent layer over a dry, usually lighter underlayer. The color you see is the underlayer through the glaze — an optical mix rather than a physical one — and it has a depth that palette mixing cannot reach. Classic uses: a transparent red over a pink or grey underpainting for drapery, Ultramarine or Prussian over a warm ground for deep sky, a thin earth glaze to pull a passage together. Rules: the underlayer must be dry; thin the glaze with medium, not just solvent; transparent pigments only; fat over lean.
Scumbling: the opposite move
A scumble is a thin, broken layer of an opaque, lighter color dragged over a darker dry layer so the underlayer shows through the gaps. It cools and lightens optically — mist over a landscape, bloom on a cheek, the haze on distant hills. Titanium White with a little of the local color is the usual scumble.
Choosing palette mixing or layer mixing
Palette mixing is predictable, fast and what a recipe describes: it gives you a known color in one go. Layer mixing gives luminosity and lets you adjust after the fact, at the cost of drying time. Many painters block in with opaque palette mixes at the right value, then glaze and scumble to push temperature and chroma. If you work that way, mix the underpainting slightly lighter and cooler than the final color, because the glaze will darken and warm it.
TerracottaRecipe by paint setMustard YellowRecipe by paint setTealRecipe by paint setSky BlueRecipe by paint set
Transparent and opaque versions of the same hue
Many hues come in both: Cadmium Red (opaque) and Alizarin or Quinacridone (transparent); Cadmium Yellow (opaque) and Indian or Transparent Yellow; Cerulean (opaque) and Phthalo Blue (transparent); Mars Black (opaque) and Ivory Black (semi). Owning one of each lets you cover and glaze without changing hue.
Questions
What is the difference between opaque and transparent oil paint?
What is glazing in oil painting?
Why do my mixed colors dry darker than expected?
