Toned grounds

A ground is the layer you paint on. A toned ground is one that isn't white: either a thin, even wash of color brushed or rubbed over the white priming (often called an imprimatura), or color mixed into the priming itself.

Painters tone a ground for a few reasons:

• It takes away the glare of white. On bright white, almost every color looks darker than it will once the canvas is covered, so it's easy to paint too light.
• It gives you a middle value to work from. You judge lights and darks against it, and can build up toward both.
• It holds the picture together. Where the ground shows through, or between strokes, the same color runs through the whole painting.
• It's faster. A toned ground can already be the shadow color or the color of the sky, so less of it needs covering.

The same paint can look surprisingly different on different grounds: a transparent red glows on white and nearly disappears on a dark red-brown, and a pale yellow looks brighter on grey than on white. That's why Pigfolio lets you change the ground behind every paint.

• Chalk gesso. Medieval and early Renaissance panels were primed with white gesso of chalk or gypsum in animal glue, smoothed until it was nearly flawless. Paint sat on a bright white.
• Verdaccio. Cennino Cennini's handbook from around 1400 describes underpainting flesh in a green-grey earth, so the warm flesh tones laid over it come alive. It's an underlayer rather than a whole ground, but painters still use the idea.
• Venetian grounds. As painters in 16th-century Venice moved to canvas, many worked on grounds toned warm grey or darker, and built light up from them.
• Red-brown grounds. In the 17th century, red-brown earth grounds (often called bole) were common in Italy and Spain, and suit paintings with deep shadows.
• Double grounds. Some Dutch painters, Rembrandt among them, used a grey layer over a red-earth one, which gives a quieter middle tone than red alone.
• Back to light. From the 18th and especially the 19th century, many painters returned to pale grounds, and the Impressionists favored white or very light ones for bright, high-key color.

These are general patterns, and individual painters, workshops and paintings varied a great deal.

• Earths are the usual choice. A thin wash of raw umber, burnt sienna or yellow ochre, or a neutral grey mixed from black and white. Umbers and siennas dry quickly in oil, so the ground is ready sooner.
• Keep it thin and lean. Thin the paint, brush it on, then wipe it back with a rag for an even, transparent tone. Oil paint should go fat over lean, so a toned layer should be leaner than what goes on top.
• Let it dry. Paint on a ground that is dry to the touch, or the tone lifts into your colors.
• Acrylic toning under oil is common and dries in minutes. Oil can go over acrylic, but never acrylic over oil.
• Middle grey for judging value. Many painters, especially those working from life, choose a neutral grey of about middle value so that every color can be judged lighter or darker against it.

Pick a ground on Explore, a paint's page or in Compare, and the paints are shown on it. The neutral greys are measured steps of lightness. The classical grounds are screen approximations of each tradition, not measurements of any painting.

• White: Lightness 98
• Pale grey: Lightness 85
• Light grey: Lightness 70
• Middle grey: Lightness 50, the 18% grey card
• Dark grey: Lightness 30
• Black: Lightness 10
• Chalk gesso: Early panel painting
• Verdaccio: Green-grey underlayer, after Cennini
• Venetian grey: Warm grey imprimatura, Titian's Venice
• Red bole: Red-brown earth, 17th-century Italy and Spain
• Double ground: Grey over red earth, as Rembrandt used
• Umber imprimatura: Thin raw umber over white
• Sienna imprimatura: Thin burnt sienna over white