Over the last few months, I have looked at most of the media used by painters to form their work, from the support of massive stone walls to the last layer of varnish. This article summarises the series, and provides links to each of its articles.

At their very simplest, paintings need only consist of three components: pigment, some binder, and a combined ground and support. The precise meaning of these terms is explained in this introduction to the series.

Simpler painting systems include fresco (and secco), encaustic, watercolours, pastels, and more ‘modern’ media such as oil pastels. Their paints or sticks are generally applied directly to a surface which functions as both ground and support.

In fresco wall painting, water-based paint is applied to wet lime plaster, and dries into that plaster layer, providing a bonding which often lasts for a millenium or more. The disadvantage is lack of mobility: the painting is one with the building, and moving them separately is very difficult and risky. In secco technique, the paint is applied to dry plaster, which results in weaker colours, less detail, and needs to be repainted periodically.

Painting in hot wax or encaustic, usually on wooden panels, has never been common, but remains very effective. The binder changes phase, from a liquid when heated for painting, to a solid at ambient temperature, which is reversible. Beeswax, with various additives, is the binder most widely used.

The binder in watercolour and gouache is gum from trees, in particular gum arabic, and the water functions as its diluent or solvent. Although long considered inferior to oil paintings, a succession of masters from Dürer onwards have made it one of the most expressive of the media, capable of a range of unique effects. Emphasis has rested on technique rather than alchemical processes.

Pastels developed quite late, and are by far the most direct form of painting: the artist applies pigment with a little gum arabic or glue binder from sticks direct to an abrasive surface, almost painting in pure pigment. Sadly, the result remains delicate and susceptible to mechanical loss. Dust from pastels is a particular danger too, and modern pastel painters often wear respiratory protection when in the studio, or have to be very careful in their choice of pigments.

More recently, crayons, oil pastels, and other stick-based media have found favour among some artists, and brought impressive results.

Three types of water-based tempera have been used: glue tempera or distemper, egg tempera, and casein derived from milk.

Glue tempera enjoyed quite a following until it became largely displaced by egg tempera. It uses a binder of animal glue, so can be rewetted and reworked when necessary. Intense colour is difficult to achieve, and over time most glue tempera paintings have faded and/or changed colour.

In contrast, egg tempera has proved highly durable. It relies on egg yolk as its binder, which dries rapidly and sets to form a hard and brittle paint layer which doesn’t rewet or rework at all. Normally applied in multiple thin layers, it was the choice of some of the great masters of the early Renaissance before being displaced by oils.

It was revived by Pre-Raphaelites and others during the nineteenth century, and again in the twentieth century by Andrew Wyeth in particular. It also resulted in the development of gesso grounds made from chalk and glue, which were initially standard for oil paintings too.

Ink and casein have been relatively unusual in finished paintings. Ink doesn’t have a binder as such, but its carbon and other pigment particles are absorbed into the surface of its paper ground. Adding shellac as a binder makes it waterproof. Casein is a protein binder not unlike egg yolk, which is made from milk with the aid of rennet, then prepared in an alkaline solution. It first became popular among illustrators, and has been little-used in fine art paintings.

Since the Renaissance, the majority of paintings by professional artists have used drying vegetable oils as their binder. The most popular of these has been linseed oil, extracted from the seed of the common flax plant, but other suitable oils are made from safflower, poppy seeds, walnuts, even soya beans. These oils slowly polymerise as they incorporate oxygen, taking months or years to ‘dry’ in depth; the presence of water and some other substances can instead result in the formation of soap, and a very weak paint layer prone to delaminate from its ground.

Because of its longstanding popularity among painters, a great deal of development has taken place in materials and techniques. Originally paints were freshly ground by assistants in the workshop, and far from portable. They first became available in ‘bladders’, then during the nineteenth century in metal tubes. These make it practical to paint in oils almost anywhere, so long as you can bring your wet canvas back.

In the late twentieth century, acrylic emulsions started to replace oils. While oil paints, even today, have firm roots in alchemical practices, acrylics are very much a product of industrial chemistry, with carefully-formulated thickeners and other media, surfactants and all manner of polymer trickery. Early paints were rather crude and limited in their pigments, but during the 1960s and 70s became much more sophisticated. However, they still have the fundamental limitation that they dry relatively quickly in comparison with oil paints, and can’t be reworked, which limits techniques.

Oils and acrylics last best when applied to relatively rigid surfaces. The most popular supports for them have been wood panels and stretched fabrics, although some artists have preferred sheets of copper and other materials.

Painters like Adam Elsheimer specialised in applying their oils to copper plates, which give his small but exquisitely-detailed paintings a distinctive look. Copper provides a smooth surface compared to the texture of woven fabrics stretched in ‘canvases’. Early gesso grounds have progressively been replaced by thinner ‘oil grounds’, which have allowed some artists to let the weave show through. Arnold Böcklin’s Sirens below is of particular interest here as it was painted with (presumably egg) tempera.

Although paper has generally been frowned upon as a support and ground for oils, it has a long and very respectable history, including playing a key role in the development of painting in front of the motif, en plein air, by landscape masters such as Pierre-Henri de Valenciennes (1750–1819) and Camille Corot (1796-1875). Aōdō Denzen’s painting above is notable as his paints use perilla rather than linseed oil as their binder, and are applied to paper, which was first made in south-east Asia.

At the end of all these media, the painting may be protected by glass, or varnish applied onto the paint layer. Like so many processes in painting, varnishing is both friend and enemy. Many varnishes contain hard resins derived from the sap of trees, which protect the surface of the paint from physical damage. But old varnish turns grey or brown and becomes dirty, requiring periodic removal and re-varnishing. In the late nineteenth century, some artists instructed owners of their works never to varnish them, so that their soft matte surface wouldn’t be obscured.

One fact you can always be certain of in painting media is that, if one artist has decided how to do something, another will have done the exact opposite – which helps ensure that every painting remains unique.