Glossary

Annual ring

wood layer created each growth season (in the temperate zone). It is composed of the earlywood and the latewood, which are more or less distinct, depending on species. Annual rings are distinct in softwoods and ring-porous hardwoods. In diffuse-porous hardwoods the borders are less visible. The appearance of the annual rings on the transverse surface is as circles, on the radial surface as parallel lines and on the tangential surface usually as parabolas. Some timbers feature undulated annual rings (on the transverse surface).

Burr

or also called burl. It is a kind of figure. It is a wartlike, deformed growth that occurs usually on the root of trunk. The wavy or twisted fibres result in a characteristic figure.

Diffuse-porous hardwoods

pores of more or less the same diameter (as seen on the transverse surface) are spread evenly over the whole annual ring. No matter if visible to the naked eye or not.

Earlywood

a part of the annual ring that is created at the beginning of the growth season. In the case of the softwoods it is the lighter part of the annual ring (as seen on the transverse surface). In the case of the ring-porous hardwoods it is the zone of visible pores arranged along the annual ring border. In the case of the diffuse-porous hardwoods it is not possible to distinguish the earlywood from the latewood. The transition between the earlywood and the latewood is the important feature for softwoods identification.

False heartwood

is a kind of wood defect. It is affecting timbers that are characterized by the absence of the heartwood. It is a discoloration of the central part of a tree, usually irregular in shape (as seen on the cross-section). It develops because of fungal attack, mechanical injury or other unfavourable factors.

Figure

special or unusual markings that may be found on the surface of wood (typically on side-grain surfaces). It comprises a combination of colour, grain, lustre and can be brought about by peculiarities of normal growth through to defects or abnormalities. Different kinds of figure can appear depending on the way the wood is cut. Burr, bird’s eye or curly are examples of some demanded ant decorative figures.

Grain

the arrangement of the fibres that forms the timber or the pattern produced by fibres on the surface of the timber. The term relates to characteristic pattern of the timber, compared to the term figure that refers to irregularities.

Hardness

additional feature in the terms of timber identification. It does not mean exact measurement of the hardness with special device, but estimation and categorisation into three basic groups (soft – medium hard – hard timbers).

Hardwoods

timber of broadleaved species (Angiospermae), characterised by features that make it possible to distinguish them from softwoods. It is especially more complex structure, often visible rays or pores. More complex structure usually results in more interesting figure. It has nothing to do with the hardness of the timbers from this group. It comprises ring-porous hardwoods, with quite distinct annual rings borders, and diffuse-porous hardwoods, with less visible annual rings borders.

Heartwood

is a central darker part of a stem, compared to the lighter sapwood at the peripheral part. Timbers can differ in colour and width of the heartwood. The transition from the heartwood into the sapwood can be abrupt or gradual.

Latewood

a part of the annual ring that is created in the second half of the growth season. In the case of the softwoods it is the darker part of the annual ring (as seen on the transverse surface). In the case of the ring-porous hardwoods it is the zone of invisible pores. In the case of the diffuse-porous hardwoods it is not possible to distinguish the latewood from the earlywood. The transition between the earlywood and the latewood could be helpful feature for softwoods identification.

Pith

a soft and light tissue that is situated in the centre of a tree. The diameter of the pith is several millimetres, depending on the species. It is usually round (as seen on the cross-section), but some exceptions in the terms of shape are possible.

Pith flecks

distinct dark lines or dots, visible on the all surfaces. They are limited just to one annual ring and the appearance is not much influenced by the surface, so they should be never mistaken with rays.

Pores

a term used for vessels. They are present only in the hardwoods. Visibility of pores depends on species. If visible, the appearance on the transverse surface is as small openings and as grooves on side-grain surfaces.

Radial surface

is produced by sectioning a stem through its pith. It is cut at right angle to the annual rings. The annual rings appear as longitudinal strips.

Rays

bands running from the pith to the bark, perpendicularly to the annual rings. That is the reason they look different depending on the surface. Visibility of rays depends on species. They are visible on the all surfaces in some timbers, only on the radial surface and in some species they are not visible.

Resin canals

present only in some softwoods. There are more or less visible depending on species. The resin canals are visible on the side-grain surfaces as short lines or as light dots on the transverse surface. Occurrence of the resin pockets or the resinosis can be regarded as the evidence of the resin canals presence.

Resin pocket

small holes filled with resin. The occurrence of the resin pocket is characteristic for softwoods with the resin canals presence.

Resinosis

local increase in resin content in timber due to the injury. It results in colour changes of the timber. It is affecting softwoods with the presence of the resin canals.

Ring-porous hardwoods

the annual ring features the presence of pores of two different diameters. The large ones are visible to the naked eye and they are arranged along the annual ring border in the earlywood. The pores of the small diameter are located in the latewood and they are not visible to the naked eye. In some timbers the small pores form characteristic bands that are well visible.

Sap stain

a bluish discoloration of the sapwood. It is caused by the growth of fungi in the interior and on the surface of wood. It is quite frequent in the case of pine, but it can also affect the sapwood of other timbers (e.g. spruce).

Sapwood

is a peripheral lighter part of a stem, compared to the darker heartwood at the central part. Besides colour, the width of the sapwood and its transition into the heartwood are the features of interest.

Semi-ring-porous woods

a transitional group between the ring-porous and the diffuse porous hardwoods. They exhibit a gradual transition of pore size from the earlywood to the latewood (walnut) or greater concentration of pores into the earlywood (cherry).

Softwoods

timber of coniferous species (Gymnospermae), characterised by features that make it possible to distinguish them from hardwoods. It is especially marked difference between the light earlywood and the dark latewood. That is the reason the annual rings borders are quite distinct. Rays are not visible to the naked eye. Pores are not present. In some species the resin canals are present.

Surfaces

because of the arrangement of the annual rings in a tree, it is necessary to consider the wood structure from three-dimensional view. Three basic sections (planes) with different orientation to the stem axis (pith) are possible to cut through the stem, providing three basic surfaces – transverse, radial and tangential surface.

Swirl

growing irregularity, characteristic for some timbers. Fibres are growing unevenly, not following the direction of the stem axis,. The cross-section of the stem differs from circular shape.

Tangential surface

is produced by sectioning a stem parallel to the stem axis (pith), but not passing through it. It is cut at a tangent to the annual rings. The annual rings appear usually as curves.

Transverse surface

is produced by sectioning a stem perpendicularly to the stem axis (pith). The annual rings appear usually as cirles.

Vessels

a kind of components forming timber that are present only in the hardwoods. The equivalent term that is used more frequently for vessels is pores.

Weight

additional feature in the terms of timber identification. It does not mean exact measurement of the weight with special device, but estimation and categorisation into three basic groups (light – medium heavy – heavy timbers).