HISTORICAL MATERIALS/TECHNIQUES

WOODEN SUPPORTS

Contents

The History of Wooden Supports

A support is the surface that physically supports the painting. The use of wood as a support for paintings dates to at least the second century in Egypt.  Wood remained the favored support for traditional painters until the sixteenth century, when fabric supports then became more popular due to their easy portability and reduced cost. Although wooden panels were used less frequently by artists after the seventeenth century, they continue to be valued for their rigidity and stability.

Types of Wood Used

Throughout history, several types of wood have been used by artists. Wood choice is generally dictated by accessibility, cost, and workability. In some instances wooden supports can be linked to specific regions; for example European poplar (populus alba and populus nigra of the salicaceae species) was commonly used in Southern Europe while artists working in Northern Europe tended to use oak (quercus species). Other types of wood used as supports include beech, lime, spruce, pine, chestnut, cherry, mahogany, and cypress.

There are two general types of wood: hardwood and softwood. Hardwood comes from deciduous trees that drop their leaves every year while softwood comes from conifer trees that have needles. Some examples of hardwoods are mahogany, walnut, oak, birch, and maple. Some softwoods are pine, spruce, cedar, fir, and Douglas-fir.

Preparation of Wooden Supports

The orientation of a cut from the tree trunk will ultimately influence the long-term stability and preservation of the panel. The most common types of cuts are tangential and radial; radial cuts were often preferred due to their characteristic resistance to warping (see slideshow above).

Before a wooden panel can safely be used as a painting support, the wood must be allowed to dry and lose its residual moisture. This was traditionally done by allowing the panel to naturally dry out over a period of years. Guild restrictions often stipulated the length of time that a panel was to be aged before it could be use, which could be as long as ten years. The wood planks could then be split or cut into the appropriate sizes. The surface of the panel was prepared by scraping it smooth using a wood plane. Small panels could be constructed from a single piece of wood; while larger panels were created from multiple planks of wood adhered together. Wooden planks were commonly glued together with animal glue or an adhesive composed of casein and lime. Wooden battens, cleats, and other mechanical devices were used to help hold multiple planks together and to diminish extreme warping. The frames of early panel paintings were generally engaged; meaning the panels were glued into the frames before subsequent sizing and ground layers were applied. Bare wood can be seen around the edges of these panels if they have been removed from their engaged frames. The backs of many panels were left rough and show evidence of the original tool marks. Flaws in the panel may have required local patches to prevent the flaws from distorting the painting surfaces. Panel makers may have covered these blemishes with fabric, metal foil, or a thick putty. There is evidence that lead-containing paint was applied to the backs of some panels to discourage insect infestation.

After achieving the desired panel size, wooden supports generally require a size layer to reduce and even out the panel’s absorbency. Collagen glue could be extracted from many sources, including the bones of fish and the skin, hooves, or bones or animals. Animal skin was the most common source of size. Sometimes fibers, strips of fabric, and whole pieces of fine, open weave fabric were adhered to the panel as buffers to diminish the possibility of cracks in the panel extending through to the ground and paint layers.

Aging, Restoration, and Conservation of Wooden Supports

​Wooden supports are prone to several types of degradation; insect infestation, extreme fluctuations in humidity/temperature (causing warping and cracking), and structural damages are all common examples. In the past, restorers attempted to combat warping by thinning the original wooden support and then adhering a lattice-like structure, called a “cradle,” to the verso of the panel. These “cradles” were composed of vertical and horizontal wooden bars.  One set would be attached to the panel following the direction of the grain (e.g. if the grain direction was vertical, the vertical cradle members would be adhered vertically to the thinned panel) while the horizontal battens were intended to remain mobile (although as soon as the panel warped slightly, the horizontal battens became “locked.”). Past restorers believed that cradles would mitigate extreme warping of the original wooden support, and the process became common in the 14th century. However, cradling can be stressful and potentially harmful to the paint and ground layers, and thinning the original wooden support prevents us from learning about a painting’s history (e.g. from dendrochronolgy or the study of maker’s marks, etc.). For these reasons, conservators today use other methods to prevent warping and movement of wooden panels. If a panel exhibits damage from moisture or structural issues, conservators aim to not remove any original material but work towards preserving what remains. For example, if a panel shows signs of active infestation, a painting can be placed in an anoxic (oxygen-free) chamber thus suffocating whatever living organism is inside.

Dendrochronology

Dendrochronology is the biological science in which the number of rings on a tree is used to determine the age of a particular piece of wood by comparison to dated standards. Such analysis can aid scholars when attempting to date an artwork or even to pair two or more panels that may have once been connected (e.g. altarpieces, diptychs, pendants, etc.). However, the original felling date of the tree combined with the period of time the wood was stored prior to use can complicate exact dating of the execution of the painting on the support. While such analysis cannot always provide a precise answer, hundreds of paintings on oak, beech, and conifer have been successfully dated re. the date of the felling of the tree; the painting cannot have been created earlier than that date although it could have been painted significantly later

For softwood or conifer supports (e.g. spruce, fir, or pine) the growth rings can be characterized by different-sized cells produced during the early and late part of the growing season.  Hardwood trees are divided into two groups: ring-porous (e.g. oak, ash, elm) and diffuse porous (beech, popular, lime). The former group generates pronounced rings due to the formation of large earlywood vessels for water distribution followed by the formation of a more compact latewood (see slideshow above). In diffuse-porous trees the vessels are evenly distributed throughout each ring, making it more difficult to approximate the original felling date of the tree.

For more information about dendrochronology check out the PDF below or open the hyperlink to learn more about preparing and caring for wooden panel paintings.

Related Links and Resources

Dendrochronology – Yale Center for British Art

The Structural Conservation of Panel Paintings – Getty Conservation Institute

Dendrochronology of Panel Paintings – Cornell University

References

Bisacca, George and Ciro Castelli. “Italian Panel Paintings.” In The Conservation of Easel Paintings, 72-86. Abingdon, England: Routledge, 2012.

Bomford, David, Jill Dunkerton, Dillian Gordon, Ashok Roy, and Jo Kirby. Italian Painting Before 1400: Art in the Making. London: National Gallery London Publications, 1989.

Cennini, Cennino. The Craftsman’s Handbook “Il Libro dell’ Arte. Translated by Daniel V. Thompson. 1933. Reprint. New York: Dover Publications, 1960.

Dunkerton, Jill, Susan Foister, Dillian Gordon, and Nicholas Penny. “Techniques.” In Giotto to Dürer: Early Renaissance Painting in the National Gallery, 153-159. New Haven: Yale University Press, 1991.

Dunkerton, Jill, Susan Foister, and Nicholas Penny. “Preparing the Panel.” In Dürer to Veronese: Sixteenth-Century Painting in the National Gallery, 211-222. New Haven and London: Yale University Press and National Gallery Publications, 1999.

Kirsh, Andrea and Rustin S. Levenson. “Supports,” In Seeing through Paintings, 5-68. New Haven: Yale University Press, 2000.

Klein, Peter. “Wood Identification and Dendrochronology.” In The Conservation of Easel Paintings, 51-72. Abingdon, Oxon England: Routledge, 2012.

Wadum, Jørgen and Noëlle Streeton. “History and Use of Panels or Other Rigid Supports for Easel Paintings.” In The Conservation of Easel Paintings, 51-115. Abingdon, Oxon England: Routledge, 2012.