Technique · Fields
Impasto
Thick paint in two kinds: broad scraped blocks of colour, or a storm of palette-knife strokes, lit so every ridge and bristle stands up.
Impasto is a field drawn for every pixel by the graphics chip. Every piece on Synapse Drip is made from a recipe that layers techniques like this one, and you can change any of it in the Studio.
Good to know
- Frank Auerbach laid paint on so thickly in some of his portraits that it stands out from the canvas in ridges; Nicolas de Stael built his paintings of the early 1950s out of thick blocks of colour put on with a palette knife.
- Hans Hofmann's paintings of the 1950s and 1960s, with their floating rectangles of strong colour, showed how a few thick blocks can make a picture push and pull.
- Rembrandt's late portraits use paint thick enough to catch light on its own: a ridge on a sleeve or a dab on a pearl becomes a highlight because it faces the light.
- The word impasto comes from the Italian for paste or dough; Titian and Rembrandt used it for highlights, and by the 1880s Vincent van Gogh was laying paint on in ridges that stand out from the canvas.
- Acrylic paint, which dries in minutes and stays flexible, became available to artists in the 1950s: Liquitex sold the first water-based acrylic paint in 1955.
The mathematics
- The paint is a height field: a stroke is a rounded bar or a rectangle given by a signed distance d, and the surface normal is worked out from the slope of d near the rim and of the bristle noise, n = (-dh/dx, -dh/dy, 1) after scaling by the thickness setting 1.10; lighting is then the dot product of n with the light direction.
- Bristle streaks are noise stretched along the stroke: it changes about twenty times faster across the stroke than along it, which gives parallel ridges without drawing any line.
- Each pixel looks at the strokes of a few neighbouring cells in two layers and keeps the one with the highest depth, the same painter's rule as drawing back to front but done by comparison, so the number of strokes does not slow it down.
In art
- Colour-field painters such as Mark Rothko built pictures from a few soft-edged blocks of colour, and the chunky blocks here belong to the same family as the thicker, more physical painters who followed.
- Abstract expressionists like Willem de Kooning treated the stroke itself as the subject: every ridge records the speed and direction of the hand that made it.
More ways to use it
Related techniques
Nebula and stars · Liquid · Droplets · Network · Terrain and maps · Neuron · Order to chaos · Fractal tree