Transparent glazing colors

A glaze is a thin, transparent layer of color over dry paint. Light passes through it, bounces off the layer underneath and comes back tinted, like light through stained glass. That's what gives glazed paintings their depth and glow, and it lets you adjust color and value without repainting.

1. Let the layer underneath dry to the touch at least; a glaze over wet paint just mixes in.
2. Mix a transparent color with a little glazing medium: traditionally linseed or stand oil thinned with solvent, or an alkyd medium if you want it dry by tomorrow.
3. Brush it on thinly with a soft brush, then soften or wipe back with a lint-free cloth to control the strength.
4. Let each glaze dry before the next. Several thin glazes look richer than one thick one.

Fat over lean: each layer should have a little more oil than the one beneath it, so upper layers stay flexible and don't crack. Use only as much medium as you need; too much can wrinkle or yellow.

• Imprimatura: a thin, transparent tint (often burnt sienna or raw umber) over the white ground, to kill the glare and set a warm or cool key.
• Grisaille: the whole picture painted in greys first. Glazes then add the color, which is how many Renaissance and academic painters worked.
• Brunaille: the same idea in browns, warmer and quicker to glaze over.
• Verdaccio: a green-grey underpainting under flesh, the traditional way to get cool half-tones in skin.

Fast-drying earths (umbers, siennas) and alkyd colors are the usual choices for underpainting, so you can glaze sooner.

• Transparent, high-tinting pigments: quinacridones (PV19 Quinacridone Violet / Rose / Red, PR209 Quinacridone Red), phthalos (PB15 Phthalo Blue, PG7 Phthalo Green (blue shade)), perylenes (PR149 Perylene Red) and dioxazine violet (PV23 Dioxazine Violet).
• Transparent iron oxides (PR101 Red Iron Oxide (Mars / Burnt Sienna), PY42 Yellow Iron Oxide (Mars Yellow) in their transparent grades) give warm, glowing earth glazes.
• Lightfastness matters more in glazes than anywhere else: a thin film has little pigment to fade before it shows. That's why the list below only includes very good or excellent ratings.

A scumble is the opposite move: a thin, broken, semi-opaque layer of a lighter color over a darker one, which softens and cools. Most painters use both.