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Wood School

Glossary of timber related terms

Here you can find  a glossary of terms found on this and other websites including those relating to:

Timber – weight, shape and form

Botanical Name – This is the only definitive way to name a timber.  Vernacular and trade names are notoriously inaccurate in this regard.  It is also possible to assume some familial similarities between timbers in the same genus.

Density – In our catalogue we give the densities of the timbers in kilograms per cubic meter.  Water has a density of 1000kg/m3 so any timber with a higher density than that will sink in water.

The density of the timber can be used as an indication of the hardness, strength and comparative workability of a timber.

Two square Edged – Most imported timbers come to us sawn with two square edges.  This saves on shipping space and excludes infestations of bark dwelling insects.  In higher grade it can normally be assumed that most objectionable defects such as sapwood, heart shake, ring shake and most knots will also have been removed.  Packs of 2SE lumber are usually made up from boards yielded from many different logs and colour and grain matching are often necessary.

One square edged – Some larger logs are sawn this way for the convenience of the sawmill and to make the boards easier to handle.  The log is first sawn down the middle and then each half log is milled to boards square to the original sawn face leaving one edge square and one edge waney.  It can be assumed that some objectionable defects and sapwood will be present.

Through And Through – A simple milling method typically used in the cutting of smaller diameter logs and almost universally used by UK sawmills for native hardwoods.  Planks are sawn in sequence from the ‘crown’ of the log and have two waney edges.  All objectionable defects will still be present.

Squared logs – A method sometimes used to present small exotic timber logs.  Four faces are cut around the log to remove worthless sapwood and to expose the beauty of the wood within.  This method also makes logs stackable and stops them from rolling about during shipment.

Cylinders – Lathe turned logs with most of the sapwood removed.  A method normally associated with Lignum Vitae.

Flitch – A trimmed up portion of a log usually of heavy section produced with the intention of further conversion into veneer or more finely wrought pieces of solid material.  Sometimes also referred to as billets or cants.

Dimension Stock – 2 Square edged boards or squares sawn to fixed sizes suitable for specific purposes.  For the sake of convenience we usually price this sort of stock per piece.

150mm wide and wider, 1900mm long and longer – an indication of board size that is self-explanatory.  It can be assumed that a smaller minimum specification will also indicate a smaller maximum board size.

Part Seasoned – The wood is in the course of being air dried and would require further drying to be reliable for any use.  Moisture content will be above 16%.

Kiln Dried – The wood has been subjected to one of several different drying procedures that leave it with a moisture content suitable for interior work.  Moisture content between 6 and 11% depending on country of origin.

Air Dried – The wood has reached the end of the natural seasoning process and will have moisture content perfect for exterior work but for interior work will need extra drying in a kiln or an acclimatisation period inside a heated room to make it reliable in service.  Moisture content is normally between 12 and 16%.

MBFT – Thousand board feet – a volume measure used in the USA when dealing with larger quantities of wood.  This measure is equivalent to 2.36M3 and 83.333Ft3

M3 – Cubic meter – a volumetric measure of timber useful in large transactions and standard in the UK hardwood trade but a big unfriendly unit of measure for small transactions.

The simplest way to calculate the volume of a board in M3 is to treat length, width and thickness as meters or part meters, for example a board 3.3meters long by 250 mm x 26mm would be 3.3 x 0.25 x 0.026 = 0.02145m3

Ft3 – Cubic foot – a traditional imperial volumetric measure of timber that remains in use because it is more user friendly for small transactions and because some of us do not know how to move on.  There are 35.315 Ft3 to the M3.

The simplest way to calculate the volume of a board in Ft3 is to multiply length, width and thickness in inches and divide by 1728.  There are probably other simple ways but that is what I use.

BDFT – Board foot - A unit of volumetric measure for hardwoods very widely used in the USA.  It is the equivalent of a piece of wood 12 x 12 x 1”.  There are 12 board feet in one cubic foot and about 424 board feet in one cubic meter.

Ft2 – Square foot– an imperial measure representing the equivalent of 12 x 12” widely used for veneer and thin stock.  There are 10.78 Ft2 to the M2.

M2 – Square meter – a metric measure representing the equivalent of 1000mm x 1000mm widely used for veneer and thin stock.

Kg – Kilogram – some timbers are sold by weight because an accurate measure of volume is not practical.  For the mathematically minded it is possible to calculate the equivalent price per  Ft 3 by multiplying the density in kg per M3 by 28 the multiplying by the price per kg and dividing by 1000.  Metric calculation is simpler, multiply the density in kg per M3 by the price per kg and you have the price per M3.

Hoppus measure – a form of measurement specific to round logs, it creates an allowance of about 27%  for waste in conversion.  The calculation is length in feet to the nearest  ½ foot x quarter girth x quarter girth divided by 144.  Sounds archaic but is still used in the home grown hardwoods industry.

String measure –a form of measure specific to round logs making no allowance for waste in conversion effectively treating the log as a cylinder.  Widely used in Europe.

Figure in wood – terms used to describe ornamental markings or designs in wood.

Ripple -  a beautiful wood figure caused by the buckling of wood fibres in the growing tree.  The fibres buckle in an even wave like pattern and become more intense as the tree matures suggesting that the fibres are getting longer year by year as would be natural to create height in the tree but are held back by the core and the problem is solved by the extra distance travelled as the fibres buckle in this way.

Ripple figure is most famous in Maple or Sycamore and will be familiar as a book match on the backs of violins, hence the alternative name for this figure ‘fiddleback’.  Other names used for it include flamed, curly and tiger but those terms can be confusing because they are sometimes used to describe other types of figure in wood.

Fiddleback – Another term for ripple figure deriving from the frequent use of book matched panels of rippled maple or sycamore for violin backs.

Flame – A term used by some to describe ripple figure e.g. flamed maple, but also used by others to describe curl figure e.g. flame mahogany.  The use of this term should be discouraged because it is confusing.

Curly – The term preferred in the USA to describe ripple figure e.g. curly maple.  It should not be confused with term curl e.g. curl mahogany that is in proper use in the UK to describe a different type of figure.

Tiger – A term sometimes used in the USA to describe ripple figure e.g. Tiger maple.  It should not be confused with ‘tigerwood’, another American term sometimes used as an alternative name for Goncalo alves (Astronium fraxinifolium)

Quilt – Quilt or quilted figure has the appearance of folds, waves or blisters and shows best on crown or slab cut faces.  The likely cause might be the same as for ripple figure but the outcome different.  It is quite a rare figure and is associated with North American maples, where currently the main use is for guitars, and with old growth European Ash (Hungarian Ash ) that went through a vogue in the late 19th century for furniture.

Blister – Another term used to describe quilted figure.

Pommelle – Another term to describe quilted figure but associated only with Sapele and Honduras Mahogany.

Block Mottle – The fibres are buckled in a way that results in the wood apparently being patterned with almost geometrically shaped blocks due to intermittent changes in the direction of the grain when viewed on radial surfaces.  Causes are probably similar to ripple figure.  This type of figure is frequently associated with Makore.

Beeswing – A miniature version of block mottle usually combined with a tight interlocked grain and very often seen and admired in Sri Lanka Satinwood.

Curl – a beautiful feathery figure in the wood formed for a short distance at the junction point where the main stem of the tree divides evenly to two branches.  Usually presented as veneer and associated with Mahogany and Walnut.

Crotch – The point where the main stem of the tree divides evenly to two branches.  Crotch figure is another term for curl figure.

Swirl – the figure in veneers taken from the zone just beyond where the best curl figure veneers are taken.  The resulting figure is like crown figure but much more spectacular.

Crown – the figure in wood produced by the growth rings on tangentially cut boards.  The centre of the board shows the annual rings as elongated ovals and parabolas with the edges of the board usually showing the annual rings as straighter lines.

Flat – Flat sawn – Figure is the same as crown

Slab – Slab sawn – Figure is the same as crown.

Plain – Plain sawn – figure is the same as crown.

Rotary cut – Only associated with veneer cutting and plywood.  The logs are peeled in one continuous piece around the circumference of the tree following the annual rings.  The figure looks like the contour lines on a map and are consistent across the entire width.  Birds eye maple veneers are prepared this way.  Kevasingo is specifically Bubinga that has been rotary peeled for the elaborate patterns that can result.

Quarter – the figure in wood produced by the growth rings on radially cut boards.  The growth rings run as more or less straight parallel lines.  The figure is sometimes enhanced by colour variations in the wood and when accurately quarter cut an additional pattern can be produced by the medullary rays variously known as silver grain, flower, silky or lace.

Rift – another term for quarter sawn.  Used by some to describe wood less exactly cut on the quarter and therefore lacking the showiness of the medullary ray figure.

Silver grain – The figure in wood produced by the medullary rays when the wood has been accurately quarter sawn.  Most often associated with oak.

Flower – Another term for silver grain.

Lace – The figure in wood produced by the medullary rays when the wood has been accurately quarter sawn, but specifically used where the medullary rays are very numerous.  This term is most commonly associated with the quarter cut wood of the London Plane tree.

Silky – another term for lace figure.  This term is most commonly associated with Australian timbers such as Silky Oak.

Ribbon – The figure that results from spiral growth in the tree that regularly changes direction every few years or so.  For a period the spiral growth will be clockwise, then anti clockwise, and so on.  Ribbon figure is common in tropical hardwoods and scarce in temperate hardwoods.  It is often seen in quarter cut pieces of sapele and mahogany.

Interlock – Interlocked grain and interlock describe the same feature as ribbon figure.

Waney edge – The waney edge is the part of a board that was originally the outside part of the tree with the bark on it.  T & T sawn boards have 2 waney edges, 1SE boards have 1 waney edge.  Waney edged boards are mostly associated with homegrown or locally sourced wood where considerations such as shipping and the spreading of diseases do not come in to play.  Waney edge is not strictly speaking a type of wood figure but it is sometimes used as an interesting visual effect for table tops and rustic work.

Natural edge – This term describes much the same thing as waney edge but it is mostly associated with turned wooden bowls where the outside layer of the tree has been used as the rim of the bowl.  Good effects are achieved using natural edge using burrs and using small diameter logs.

Burr – Abnormal growth resulting from an area of the trunk of the tree sending out a multitude of dormant buds in increasing amounts year by year.  Burrs usually appear as a bark covered blister or bulge on the outside of a tree.  Sometimes burrs are concentrated at the base of a tree, sometimes the entire bole of a tree can be burr.  Some valuable burrs grow underground as a root ball.  Examples of this would be Thuya burr and Briar.

Burr figure shows as hundreds of closely packed small knots surrounded by contorted and gnarly wood tissue.  The best presentation of burr figure is on tangential faces where the small knots are seen head on.

Burl – What an American calls burr figure.

Cluster – Boards or veneers where small patches of burr are separated by non-burry wood that is contorted or rippled.

Cat’s paw – very small patches of burr are spread all over a board with normal wood in between.  Oak is often associated with this term.

Pippy – Many small individual knots are scattered over a board to decorative effect.  Usually associated with Oak and Yew.

Masur – The German language term for burr – or –

In the case of Masur Birch it is a figure found in a genetic variant of European birch – Betula pendula var. Carelica.  The figure shows as twists and contortions combined with darker zones that are either pith flecks or ingrown bark pockets.  Quite unique and technically not a burr at all.

Bird’s eye – A type of figure usually associated with American rock maple (Acer saccharum) but also occasionally found in other species.  It is formed when the cambium (the growing layer of the tree between the sapwood and the bark) is damaged in multiple small areas causing pits to develop where the wood has not formed.  The cambium then repairs itself and the subsequent layers of growth follow the contours created by these small pits and continue to do this for many years.

Not to be confused with any burr or burr derived figures.

As yet no one has conclusively explained why this happens to the tree, I once heard that it was normal to find several trees together with bird’s eye figure but this could imply cross infection, genetics, or growth conditions as the cause.

Tiger claw – Rather specific to Sonokeling rosewood, an area of abnormal figure and ingrown sap caused by injury to the cambium ( growing layer ) of the tree by an animal of some kind.  Defect or figure depending on your point of view.

Gum vein – The equivalent of a resin pocket but specific to hardwoods rather than softwoods.  Often associated with Zebrano where the gum sows as a black crystalised substance in a pocket in the wood and frequently found in a range of Australian trees such as Salmon gum and Jarrah.  Defect or figure depending on your point of view.

Pith fleck – Not in any way connected to the pith of a tree which is the small point of soft tissue at the very centre of a log.  Pith flecks show as irregular discoloured streaks of tissue in wood and are probably caused by damage to the cambium ( growing layer 0 of the tree by insects.  Common in Birch and American cherry. 

Heart and sap – Sapwood is the outer part of the living tree that contains the living cells in the growing tree (Alburnum), heart wood is the inner part of the tree (Duramen) not normally made up of living cells.  Many trees such as Sycamore, Beech and Ash do not show a visible difference in colour between the sapwood and heartwood.  Sapwood is normally shades of yellowish or greyish white and timbers with strong  colour to the heartwood can show quite dramatic variations.  The width of the sapwood in a tree can vary from a few millimetres to several centimeters.  Sapwood and heartwood have different properties to each other and this is most dramatically revealed in the English longbow where the heartwood works brilliantly in compression and the sapwood is brilliant in tension.  The rule of thumb however is that the sapwood has fewer virtues than the heartwood and may give trouble over time.  European walnut sapwood for example is a worm magnet, the heartwood is not, for that reason it would be better excluded form a piece.

Heart and sap figure is where the sapwood edge is used for dramatic effect in a piece for example as a table edge or in matched sequences of 2 or more when veneering a panel.

TO BE CONTINUED

This is a work in progress and additions will be made from time to time. Future items will include:

Medullary ray

Silk

Radial

Tangential

Ring porous

Diffuse porous

Spring growth

Summer growth

Early wood

Late wood

Lace

Wormy

Tiger

Stripe

Fumed

Brown

Bog

Lustre

Chatoyance

Figure

Texture

Iron stain

Plum pudding

Watermark

Spider web

Partridge

Masur

Olive

Porcupine

Knotty

End grain

Spalted

Defect in timber

Heart shake

Ring shake

End shake/end check

Surface check

Hairline cracks

Honeycomb

Collapse

Case hardening

Ingrown bark

Worm

Dote

Blue stain

Decay

Fungal stain

Spalt

Wind

Twist

Warp

Knots

Sound knots

Spike knots

Pin knots

Dead knots

Gum vein

Resin pocket

Rind gall

Cross grain

Spiral growth

Short Grain

Run out

Wandering heart

Tension wood

Compression wood

Cup

Bow

Crook

Price – A defect in wood that can never be overcome.