Glossary
Term | Definition |
---|---|
Arris |
Intersection of the face and edge of a piece of wood. |
Backsawn timber |
Timber that is sawn so that the growth rings are inclined at less than 45 degrees to the wide face. |
Bound moisture |
Moisture which is bound up in the cell walls of wood fibres. |
Bow |
Curve in the lengthwise direction of a board causing the wide face to move away from a flat plane. |
Cambium |
Thin layer of tissue between the bark and sapwood that subdivides to form new wood and bark cells. |
Check |
Separation of fibres along the grain – generally caused by drying stresses – but not extending from one surface to another. |
Collapse |
Flattening of cells during the drying process, caused by the cell walls buckling under the changing pressure. |
Compression |
Force that tends to crush the wood fibres. |
Cup |
Deviation across the surface of a board that causes it to curve away from a flat plane. |
Decay |
Decomposition of wood, caused by fungi. |
Density |
Mass, or weight, of a block of wood, expressed in kilograms per cubic metre. |
Durability |
Natural resistance of timber to fungi and insects. |
Earlywood |
Less dense part of a growth ring – also called 'springwood'. |
Equilibrium moisture content (EMC) |
Moisture content in balance with the surrounding atmosphere. |
Fibre saturation point |
Point in seasoning where the cell cavities are free from water but cell walls are still saturated with bound water – generally about 25-30% moisture content. |
Free moisture |
Moisture which is present in the cell cavities of wood. |
Grain |
General direction of the wood fibres. |
Green |
Unseasoned timber. |
Growth rings |
Rings on the cross section of a trunk marking cycles of growth. |
Gum vein |
A ribbon of gum between growth rings. |
Gum |
A natural substance, also called kino, produced in trees as a result of fire or mechanical damage. |
Hardwood |
Timber classified botanically as 'angiosperms', with a cell structure characterised by 'pores' (also called 'vessels'). |
Heartwood |
Wood containing dead cells that make up the centre part of the tree, and often filled with phenolic compounds, gums and resins. |
Honeycombing |
Drying defect that results in internal cavities. |
Kiln |
Enclosure used for drying timber under controlled conditions. |
Knot |
Cross section of a branch that has been surrounded by wood tissue in the stem. |
Latewood |
Denser wood in a growth ring – also called 'summerwood'. |
Moisture content (MC) |
Weight of moisture contained in a piece of timber – expressed as a percentage of the weight of the woody substance. |
Pith |
Soft core in the centre of a tree trunk or branch. |
Quartersawn timber |
Timber that is sawn so that the growth rings are inclined at more than 45 degrees to the wide face. |
Sapwood |
Outer layers of wood in the growing tree containing living cells. |
Seasoned timber |
Timber that has been dried to within a specific moisture content range – generally 10% to 15%, unless otherwise specified. |
Shake |
Separation of wood fibres caused by stresses in the standing tree or during the felling or processing stages – but not caused by drying stresses. |
Shrinkage |
Reduction in dimension or volume that occurs when the moisture content is reduced below fibre saturation point. |
Softwood |
Timber classified botanically as 'gymnosperms', with a cell structure that does not contain pores. |
Split |
Defect that occurs when stresses cause the wood fibres to separate and form cracks that run from one surface to another. |
Spring |
Lengthwise curve of the edge of a piece of timber, not affecting the face. |
Tension |
Force that tends to pull wood fibres away from each other. |
Unseasoned timber |
Timber that has not been seasoned. |
Wane |
Presence of the original underbark surface, with or without bark, on the face or edge of a board. |
Want |
Absence of wood, other than wane, from the face or edge of a board. |
Warp |
Variation from a true surface, including bow, cup and twist, generally caused by irregular seasoning. |