Selecting Wood for Painting Panels

Beginning with this installment, this series of articles discusses the technique of making icons in great detail, from obtaining the wood for the painting panel to putting on the final picture varnish or olifa of icons. A guide to wood properties and selecting the optimal wood for painting panels. This is the first in a series of articles on painting icons, beginning with selecting the panel, preparing it for painting, and the painting technique. Although this series of articles applies specifically to the preparation and painting of icons, it has a wider application for preparing solid wood panels for painting.


Before approaching the examination of the stages of icon painting, I want to remind all of those reading these words of the following: Since ancient times, icon painting has been considered a spiritual pursuit; therefore, the work of the iconographer must not be placed among the ranks of a hobby, or as a way to kill time. Iconography is a spiritual skill; therefore, the iconographer must understand spiritual things, which is utterly impossible if they do not attend divine service and do not participate in church life. The icons written by this iconographer will be ordinary images, perhaps even good ones, but frequently deprived of the spiritual content inherent in icons written with the observance of all the requirements of those presented to the iconographer.

Chapter 43 of the Stoglav indicates that to be an iconographer, it is necessary to be "humble, meek, reverent, not to be given to idle talk, not to be derisive, not to be quarrelsome, not to be envious, not to be a drunkard, not to be a thief, not to be a murderer; to especially be virtuous of spirit and body with godly fear, and painters should frequently come to the spiritual fathers and in everything consult with them, and profess, and follow their admonition and study to live in fasting, prayer and abstention with humbleness." Very few people at present, who consider themselves to be iconographers, meet these requirements perfectly. Therefore, after selecting the craft of iconographer, it is vital to make an effort with all of one's forces to be worthy of this work, to imitate the ancient masters who achieved perfection not only in painting icons but also in spiritual perfection.

While working on an icon, it is essential to remember prayer. Since the primary purpose of an icon is to contribute to prayer, prayer during work on an icon will help to overcome many difficulties. Furthermore, the words of the prophet of Jeremiah should be remembered, "Cursed is he who does the work of the LORD with slackness." (Jeremiah 48:10—RIV).

Selection of Wood for Painting

Approaching the painting of an icon or any other painting on a support, is necessary to prepare it for the ground. The forms of supports can be quite diverse (we will discuss this at length in another article). However, the type of wood typically used depends upon what is locally available to the painter. Not every wood is suitable for use as a painting panel; therefore, one should consider the selection of wood in greater detail. In ancient Rus, the production of icon boards was done by a doshchanik (дощаник). Doshchaniki, like all other masters, were well-informed relative to the properties of wood and were specialists in this field. In our time, most icon boards are manufactured by iconographers themselves.

Only dry wood is to be used for an icon board. One should consider that freshly-felled wood contains free or capillary water bound in its cell cavities and water in the cell walls. Whereas capillary water can be removed from the wood by air drying in a matter of one to two days, evaporation of water in the cell walls may take more than a year, depending upon the dimensions of the cut board and the density of the wood.

Wood from a freshly-felled tree must not be dry sanded or finished and must be kept in a place protected from drafts for at least one year. To avoid splitting, it is advisable to cover the transverse cuts of the wood with oil paint. Kilns are today widely used to hasten the process of drying. Although the results of kiln drying are not damaging, nevertheless kiln-dried wood does not have some of the properties inherent in air drying.

While selecting wood, it is necessary to know some things about its structure and properties. It is possible to distinguish the following layers in the transverse section of a tree (Fig. 1).

bark (phloem) 
sapwood (alburnum) 
heartwood (duramen) 

Fig. 1. The transverse section of a tree trunk, showing: 1. bark (phloem) 2. sapwood (alburnum) 3. heartwood (duramen), and 4. pith

Structure of Trees

Bark (phloem)

The tissue outside the wood of trees, consisting of phloem and other outer tissue.


All wood growth takes place in the cambium between the sapwood and the phloem. Constantly increasing in size, the cambium gives rise to wood cells from its inner face and bark cells from its outer face.

Sapwood (alburnum)

The outer wood of a tree trunk consisting of living wood cells that both conduct water and provide structural support.

Heartwood (duramen)

The wood at the center of a tree trunk consisting of dead wood cells heavily thickened with lignin and providing structural support. Many heartwood cells contain oils, gums, and resins that darken the wood.

As trees age their wood is divided into sapwood and heartwood by a process of lignification. The sapwood in the outer layers of the tree trunk contains living wood cells, carrying out water transport and storage functions, and therefore containing more moisture. For the most part, the heartwood in the center section of the tree trunk contains only dead wood cells and as consequence has less moisture. In essence, lignification is the process by which living storage cells die off. If lignification is accompanied by the deposit of colored extractives, as is the case with oak, pine and walnut, colored heartwood is formed. Many of the substances deposited in the heartwood have fungicidal and insecticidal properties. They increase considerably the natural durability of the heartwood. The ranks of durable woods are therefore dominated by those with colored heartwood, while the less long-lasting woods mostly do not have colored heartwood. All dark colored heartwood is not resistant to decay, and some nearly colorless heartwood is decay resistant, as in northern white cedar. However, none of the sapwood of any species is resistant to decay. Heartwood extractives may also affect wood by (a) reducing permeability, making the heartwood slower to dry, (b) increasing stability in changing moisture conditions, and (c) increasing weight (slightly). However, as sapwood changes to heartwood, no cells are added or taken away, nor do any cells change shape. The basic strength of the wood is essentially not affected by the transition from sapwood cells to heartwood cells.

Woods are classified as follows according to the kind of heartwood they form:

  • trees with regular colored heartwood formation, including oak, pine, walnut and willow;
  • trees with light heartwood, in which the heartwood cannot be distinguished from the sapwood by color, but has a lower water content, including spruce, fir red beech and lime; and
  • trees with delayed heartwood formation, in which there are no differences of color or moisture between the heartwood and sapwood, and signs of lignification can only be identified with a microscope. The only wood from this group used in panel painting is poplar.

The other cell complexes in wood include medullar rays, vertical storage cells and resin ducts. The pith, or medulla, acts as a store for nutrients, particularly in young trees. This dead storage tissue has a small diameter of only a few millimeters. Medullar rays are narrow bands of various forms and sizes that radiate from the core, and in some woods are not visible to the unaided eye. Icon paintings on wood that still contain medullar tubes tend to crack.

Growth Rings

In most species in temperate climates, the difference between wood that is formed early in a growing season and that formed later is sufficient to produce well-marked annual growth rings. The age of a tree at the stump or the age at any cross section of the trunk may be determined by counting these rings. However, if the growth in diameter is interrupted, by drought or defoliation by insects for example, more than one ring may be formed in the same season. In such an event, the inner rings usually do not have sharply defined boundaries and are termed false rings. Trees that have only very small crowns or that have accidentally lost most of their foliage may form an incomplete growth layer, sometimes called a discontinuous ring. The inner part of the growth ring formed first in the growing season is called earlywood and the outer part formed later in the growing season, latewood. Earlywood is characterized by cells with relatively large cavities and thin walls. Latewood cells have smaller cavities and thicker walls. The transition from earlywood to latewood may be gradual or abrupt, depending on conditions within a tree and among species. Hardwood fibers average about 1 mm (1/25 in.) in length; softwood fibers range from 3 to 8 mm (1/8 to 1/3 in.) in length.

Hardwoods and Softwoods

Trees are divided into two broad classes, usually referred to as hardwoods and softwoods. These names can be confusing since some softwoods are actually harder than some hardwoods, and conversely some hardwoods are softer than some softwoods. For example, softwoods such as longleaf pine and Douglas-fir are typically harder than the hardwoods basswood and aspen. Botanically, hardwoods are Angiosperms; the seeds are enclosed in the ovary of the flower. Anatomically, hardwoods are porous; that is, they contain vessel elements. A vessel element is a wood cell with open ends; when vessel elements are set one above another, they form a continuous tube (vessel), which serves as a conduit for transporting water or sap in the tree. Typically, hardwoods are plants with broad leaves that, with few exceptions in the temperate region, lose their leaves in autumn or winter. Most imported tropical woods are hardwoods. Botanically, softwoods are Gymnosperms or conifers; the seeds are naked (not enclosed in the ovary of the flower). Anatomically, softwoods are nonporous and do not contain vessels. Softwoods are usually cone-bearing plants with needle- or scale-like evergreen leaves. Some softwoods, such as larches and bald cypress, lose their needles during autumn or winter.


Depending on their density, hardwoods can be subdivided into medium heavy, heavy, very heavy, and woods that actually sink in water called ironwoods. Hardwoods are usually limited to flowering trees and shrubs because their wood contains water-conducting cells (tracheids and vessel elements) plus tightly-packed, thick-walled fiber cells that are lacking in the wood of conifers. Generally the cone-bearing trees, such as pines (Pinus), spruce (Picea), fir (Abies), and redwood (Sequoia), are considered to be softwoods because their wood is composed essentially of water-conducting cells (tracheids) without wood fiber cells. The weight and hardness of wood is attributed to the density of the cells, the amount of lignin in the cell walls, and the percentage of tiny air spaces or pores within the cell walls. The classification and separation of these categories is based on specific gravity.


The hardness of wood is measured as its resistance to the penetration of a foreign body into its surface. Due to its cellular structure, wood has a very uneven texture, so that it can be difficult to measure hardness. One method used is the Brinell test; 4 Brinell hardness HB (kg/mm2) is measured at 12% moisture content. All measures of hardness should only be regarded as approximations, however. The hardness numbers of all woods are equally dependent on gross density and wood moisture content.

For panel paintings it is sufficient to distinguish between panels made of harder and softer grades of wood (note: these are not the same as hardwoods and softwoods), in order to be able to predict how a panel will react to painting and climatic changes.

Among woods used in icon painting, fir, pine spruce, poplar, willow, and lime are graded as soft grades, while oak, red beech and walnut as hard grades.

Factors in the Deformation of Wood Panels

When selecting wood for an icon panel you should carefully consider the position of the cut wood relative to the tree layers. As can be seen from the illustration (Fig. 2), the deformation of a board upon drying is dependent upon its position in the layers of wood; therefore while selecting wood for a large icon panel consisting of several boards it is necessary to consider the direction of their subsequent deformation.

Wood is distinguished in one of three different directions: transverse, tangential and radial.

Fig. 2. Tendency to warp is dependent upon the boards position in the layers of the tree.

Transverse cuts run at right angles to the trunk axis, across the fibers, which means that cells and cell complexes running parallel to the axis are severed.

Tangential cuts run parallel to the trunk axis and tangential to the growth rings. This means that medullar rays are cut through at right angles. Most planks are cut tangentially. The growth rings form a U-shaped pattern in tangentially cut wood.

Radial cuts run parallel to the trunk axis and the medullar rays. Woods that form clear growth rings, such as oak, show a stripy pattern when they are cut radially. The medullar rays are cut lengthwise. This creates shiny bands and scaly patches called "ripple marks."

Transverse cut

Tangential cut

Fig. 3. Panels with transverse (top), tangential (middle) and radial cuts (bottom)

Types of Wood



Cypress (Cupressus) is an ideal wood for use in icon boards. The wood is hard, remarkably fine and close in grain, very durable, has a yellowish, pale brown, or pinkish, reddish-brown color with occasional streaking or variegation, and a characteristic fragrant scent. The texture is fine and uniform, and the grain is usually straight. The density of air-dried wood is 512 kg/m3 (32 lb/ft3), and the strength is comparable with that of yellow-cedar (Chamaecyparis nootkatensis) or western hemlock (Tsuga heterophylla). The wood is easy to work with hand and machine tools. Cypress air dries very rapidly with little or no end- or surface-checking. The merits of cypress are moderately low shrinkage (but somewhat higher than that of the cedars), resistance to warping and atmospheric changes in temperature and humidity. It is resistant to insect infestations, which is explained by the presence in the wood of aromatic resins, which discourage insect attack. A drawback of cypress is that it forms a large number of twigs.


The hardwood lime (Tilia) is one of the best types of wood for icon boards from trees growing in temperate climates. The heartwood of lime is pale yellowish brown with occasional darker streaks. It has wide, creamy white or pale brown sapwood that merges gradually into heartwood. The wood of the lime tree has a fine, uniform texture, and is straight grained and easy to work with tools. It is soft, possesses low density and, therefore, is lower in weight, which in iconography is important since painting icon requires that the board be maintained in an inclined horizontal position while being worked on, which icon painters find necessary to turn frequently. Shrinkage in width and thickness during drying is rated high, but it seldom warps, making ideally is suited for icons with carved adornments, since it is one of the best woods for carving. The deficiency of lime is its susceptibility to insect infestations. Sometimes one may find icon boards made from lime with thin sheets of cypress glued to the back sides, and also boards coated with substances that discourage insect attacks.

Some West European manuscripts of the 17th century provide recipes for treating boards to protect them from insect damage. While these recipes greatly vary, most have in common one substance, garlic juice. Many old icon boards have a dark brown or black color on the back side. Investigations show that these panels were impregnated with substances similar to the recipes mentioned in the manuscripts, and also the brown coloration is due to its being impregnated with drying oil that affords a certain protection from insect attack and atmospheric moisture. Since the first century it was already known that the wood of some trees is not susceptible to insect attacks because of the presence of aromatic substances, which discourage insects. Such types of wood were given preference in panel paintings. It was much later that the back side of icons were frequently coated with oil paint, which besides giving a certain protection from insects, protected board from warping by preventing its one-sided drying. However, this method of protection from warping is not completely effective.

Returning to the description of the selection of wood for icon boards it is worthwhile to note that the two types of wood described above, although ideal for use in iconography, are not used frequently, since cypress is almost inaccessible and lime is relatively expensive. Therefore, most icon boards are made from less expensive and more easily accessible wood.

Alder, Red

Red alder (Alnus rubra) is a hardwood. The wood of red alder varies from almost white to pale pinkish brown, and there is no visible boundary between the heartwood and sapwood. Red alder is moderately light in weight and intermediate in most strength properties but low in shock resistance. It has relatively low shrinkage. The color of alder in its freshly-felled state is white, but it darkens upon exposure to air and becomes a yellowish-red. Growth rings are indistinct, and medullar rays are not visible to the naked eye, and in the transverse section they are revealed in the form of bright, radial lines. The wood is soft, light, subject to little warping, and is very steadfast to humidity.


Ash (Fraxinus) is a hardwood tree with a light brown heartwood that gradually changes color to yellowish-white sapwood. It is dense wood that is heavy, strong, hard, and stiff, and it has high resistance to shock. As a material for icon boards it is not suitable since it checks during drying.


Aspen (Populus) is any of several poplars (especially Populus tremula of Europe and P. tremuloides and P. grandidentata of North America) with leaves that flutter in the lightest wind because of their flattened petioles. It is characterized by softness, lightweight, uniform texture, and resistance to insects. The heartwood of aspen is grayish white to light grayish brown. The sapwood is lighter colored and generally merges gradually into the heartwood without being clearly marked. Aspen wood is usually straight grained with a fine, uniform texture. It is easily worked. It can be used for icon boards, but frequently has hollows and knots, which make it difficult to use in the production of large icon panels.


Birch (Betula) is a hardwood tree with fine, uniform texture. For most species of this tree the wood is heavy, hard, and strong, and it has good shock-resisting ability. The wood is fine and uniform in texture. Birch shrinks considerably during drying. Because of its friability it is barely suitable for icon boards, although it is used. Furthermore, it reacts to changes in temperature and humidity, which leads to warping in large panels of wood. It is susceptible to fungus and insect attacks.


Maple (Acer) is a hardwood. The heartwood is usually light reddish brown but sometimes considerably darker. The sapwood is commonly white with a slight reddish-brown tinge. It is roughly 7 to 13 cm or more (3 to 5 in. or more) wide. Hard maple has a fine, uniform texture. It is heavy, strong, stiff, hard, and resistant to shock and has high shrinkage. The grain of sugar maple is generally straight, but birdseye, curly, or fiddleback grain is often found. Its properties are close to that of alder, but is a harder, stronger wood.


Oak (Quercus) is a hardwood that possesses many good qualities, but it is not suitable for icon boards due to those special features of the wood structure making it liable to crack underneath the ground, and causing its destruction. It is ideal for use as keys in an icon panel. The sapwood is nearly white and roughly 2 to 5 cm (1 to 2 in.) wide. The heartwood is brown with a tinge of red or grayish brown.


Poplar or Yellow Poplar (Liriodendron tulipifera) is a hardwood. The sapwood is white while the heartwood is a light brown. Growth rings are clearly visible in all sections. Yellow-poplar sapwood is white and frequently several centimeters wide. The wood is generally straight grained and comparatively uniform in texture. Slow-grown wood is moderately light in weight and moderately low in bending strength, moderately soft, and moderately low in shock resistance. The wood has moderately high shrinkage when dried from a green condition, but it is not difficult to dry and is stable after drying. Its properties are similar to lime, but it is softer, making less resistant to shocks, which leave dents in the wood. Without taking into account its softness, it is possible to say that poplar in practice is not inferior to lime and can be successfully used as a material for icon boards.


Fir, True

True firs (Abies) are softwoods that are among the softest and lightest of the coniferous species. The wood of true firs is creamy white to pale brown. The heartwood and sapwood are generally indistinguishable. Some species are lightweight, have low bending and compressive strength, are moderately low in stiffness, are soft, and have low resistance to shock.


Larch (Larix) is a softwood tree that has a clearly defined large dark heartwood. The heartwood is yellowish brown and the sapwood, yellowish white. The sapwood is generally not more than 2.5 cm (1 in.) wide. The wood is stiff, moderately strong and hard, moderately high in shock resistance, and moderately heavy. It has moderately high shrinkage. The wood is usually straight grained, splits easily, and is subject to ring shake. Knots are common but generally small and tight. In many respects it is similar to pine (see below), is impervious to fungus, and has exceptional frost resistance.


Pine (Pinus) is a softwood with resin ducts. The sapwood is yellow to white in color with clearly defined growth rings in all transverse sections, and marked with the sharp passage from bright earlywood to dark latewood. The wood has comparatively uniform texture and is straight grained. It is easily kiln dried, has low shrinkage, and ranks high in stability. It is also easy to work and can be readily glued. Many species of pine are lightweight, moderately soft, moderately low in strength, low in shock resistance, and low in stiffness.


Pine and spruce are outwardly different, but are difficult to distinguish in the form of wood. Spruce (Picea) is a softwood that is light in color, and with little difference between the heartwood and sapwood. Most popular species of spruce have about the same properties, and they are not distinguished from each other in commerce. The wood dries easily and is stable after drying, is moderately lightweight and easily worked, has moderate shrinkage, and is moderately strong, stiff, tough, and hard. It has a uniform texture, is white in color with a light yellow-pink nuance.

Pine, fir and larch are among the most frequently used wood in iconography, because of their accessibility and low cost. However, when using these types of wood it necessary to consider that they contain resin ducts, so that with an increase in temperature they may liberate resins that are capable of appearing on the surface of the board, sometimes even through the painting. This defect is practically unavoidable.