Oil Painting Fundamentals

Oil paint has been the medium of the old masters for over 500 years. It dries slowly, blends beautifully and allows deep, rich color and both delicate glazes and thick textures. It also has rules you need to follow so your paintings last.

Materials

• Paints: a limited palette is ideal to start: titanium white, cadmium yellow (or a hue), yellow ochre, cadmium red (or a hue), alizarin crimson (or a permanent alternative), ultramarine blue, burnt umber.
• Surface: primed canvas, canvas panels or wooden panels primed with gesso. Never paint oil directly on raw canvas or paper: the oil rots the fibers.
• Brushes: hog bristle brushes (flats, filberts, rounds) for moving paint; a few soft synthetic brushes for details. A palette knife for mixing.
• Medium: linseed oil, or a ready-made painting medium, to adjust consistency.
• Solvent for cleaning brushes and thinning early layers: use odorless mineral spirits. Or work solvent-free, cleaning brushes with oil and soap.

Fat over lean

The most important rule in oil painting:

• Lean layers have little oil (often thinned with solvent). They dry fast.
• Fat layers have more oil. They dry slowly and stay flexible.
• Paint lean first, fat later. If you put a lean, fast-drying layer over a fat, slow one, the top layer will crack as the bottom one keeps moving.

Two main approaches

Alla prima (wet-into-wet)

Painting the whole picture in one session, while everything is wet. Direct, fresh and energetic: the approach of many impressionists and plein-air painters.

1. Tone the canvas and sketch with thin paint.
2. Block in big shapes of color and value.
3. Refine, painting wet into wet.
4. Finish with thicker paint for lights and accents.

Indirect painting (layers)

Building a painting over days or weeks:

1. Underpainting: a monochrome painting (often in burnt umber or gray) that establishes drawing and values.
2. Color layers: opaque color painted over the dry underpainting.
3. Glazes: thin transparent layers of color mixed with medium, for depth and luminosity.

Working tips

• Keep it simple: thin paint in the shadows, thicker paint in the lights (a classic convention).
• Use clean brushes for each value family, or wipe them often, to avoid muddy mixes.
• Mix on the palette, not on the canvas, for clean colors.
• Varnish a finished painting only when it's completely dry (often 6 months or more) to protect it.