So far in this series, I have looked almost exclusively at the paints used to make paintings, particularly in terms of the binder that holds pigment particles to the ground. What I have largely glossed over is the equally important matter of the ground and how it is supported. This article looks at one of the most popular supports until the introduction of canvas during the Renaissance: wood panels.

Support and ground are seldom visible to those who look at paintings, unless they’re invited into a conservation workshop and see the reverse of paintings, in this case made using oils on oak panel in 1642. What looks dull and simple here is far more complex, and can determine whether the work lasts a few decades or several millenia.

The oldest surviving paintings on wood panels in Europe have been dated to around 540-530 BCE, and were found in a cave in Greece.

Far more numerous are the funerary portraits of Fayum (Faiyum) in Egypt, which were generally made using encaustic paints on cedar and other wood panels, some of which is exposed in this example. These have been so well preserved because they were sealed in constantly dry and dark environments. Woods used include lime (the most frequent), sycamore, oak, cedar, fir, pine, and beech, which were cut into thin panels ready to paint using encaustics or glue tempera.

Wood panels are ideal for most media – provided they are given a suitable ground – because they are relatively rigid, so protect the paint layer from mechanical stress, but not entirely. In climates where there are seasonal changes in temperature and atmospheric humidity (much of the more densely-populated parts of the world), wood expands and contracts with those changes. Depending on how the panel was made, it can also warp and change shape more obviously, and in the worst cases can rot or be consumed by insects or fungus. Some have had to be transferred to stretched canvas when their panels have failed altogether.

Despite these dangers, many extremely old paintings have survived very well, thanks to their wooden support. Margarito d’Arezzo’s egg tempera Virgin and Child Enthroned is now well over eight hundred years old.

Preparing wood panels for painting is a painstaking process if you want the best results. The wood itself must be of high quality, without knots or other defects which will cause problems. It should be predominantly heartwood rather than sapwood, cut radially, and carefully seasoned for anything between two and fifteen years.

For paintings of any size, it then needs to be joined to other pieces to form the whole panel. Typical oak boards are 25-30 cm (10-12 inches) across, and 0.8-3 cm (0.3-1.2 inch) thick. These were normally glued together, often using dowels to maintain alignment during joining. Panel-making was a recognised craft with high levels of skill.

The surface to be prepared for painting, and sometimes its reverse too, is then sealed with a size consisting mainly of glue, sometimes with the addition of resin and linen too. The ground is laid on top of that, and may consist of up to a dozen or even fifteen layers of chalk or gypsum with binder as a gesso. More recently oil grounds, consisting of white or tinted oil paint, have been used instead, as have layers of specially-formulated acrylic paint, known misleadingly as acrylic gesso.

There are many different formulae and processes for laying down grounds, which vary according to the type of paint to be applied.

Egg tempera paintings, such as The Wilton Diptych from about 1395-9, are notoriously brittle, and are still best made on a traditional gesso on a well-prepared panel. As the detail below shows, over the centuries they develop fine cracks which often align with grain and structure within the underlying wood, as it has expanded and contracted with the seasons.

Many of the most famous early oil paintings, such as the ‘Arnolfini Portrait’ by Jan van Eyck, are still on their original wood panels, in this case made from oak felled in the woods of northern Europe.

A surprisingly wide range of different wood has been used with success. Antonello da Messina’s Saint Jerome in his Study is painted on lime or linden.

Some artists stuck meticulously to one type of wood through their entire career, but Leonardo da Vinci’s surviving works use a range. His portrait of Ginevra de’ Benci above is on poplar, while his Lady with an Ermine below is on walnut – both typically used in southern Europe, because of their local or trade availability.

Hieronymus Bosch characteristically painted on oak, as in his famous triptych The Garden of Earthly Delights from about 1495-1505. Meticulous examination of the supports in his works has enabled them to be dated more precisely, and several have been recognised as later copies thanks to dendrochronology.

Literally the biggest problem with painting on wood panels is when they become large. Botticelli’s Primavera is slightly more than two by three metres (6.5 x 10 feet), which is heavy and difficult to make sufficiently rigid without adding further to its weight. This is made worse by the addition of gesso to prepare for egg tempera paint.

Rubens used both panels and stretched canvas for his finished works. His huge triptych in the Cathedral of Our Lady Antwerp has as its centre panel the Descent from the Cross which is over four by three metres (13 x 10 feet). At the other end of the scale are his quick oil sketches made on much smaller panels of wood.

After 1600, the use of wood panels declined quite markedly. Some artists still used them for easel paintings, and small lightweight wood panels were and remain popular for plein air landscape painting, particularly when fitted into pochade boxes.

During the nineteenth century, a new type of wood panel was developed, using several thin layers of wood laminated together: plywood. This was manufactured using rotary lathes, and by the end of that century had become popular with oil painters.

Henry Ossawa Tanner’s plein air oil painting of a Gateway, Tangier from about 1910 is a good and relatively early example of a plywood support.

Another enthusiastic user of plywood panels was the great Polish Symbolist Jacek Malczewski.

Many great artists continue to paint on wood or plywood panels, which are just as suitable for modern media such as acrylics, used here by Jeremy Gardiner in his Summer Solstice, Lundy North Lighthouse from 2016, which uses a poplar panel.