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Glossary

Veneer cutting methods

The method used to cut veneers is an important factor in producing the various visual effects. Two logs of the same species, but with their veneers cut differently, will have entirely different visual characteristics. Generally, there are three major methods of the veneer cutting: rotary peeling, slicing and half-round slicing. These methods produce different grain patterns regardless of the wood species involved.

Rotary peeling

Rotary peeling

The log is mounted centrally in the lathe and turned continuously against a knife. The veneer is “unrolled’ much like a ribbon. Since the cut follows the log’s annual growth rings, a bold variegated grain marking is produced. Rotary peeled veneer is exceptionally wide. The veneer is then clipped to width and objectionable defects are removed. This is the common procedure for manufacture of commercial veneers for construction-grade plywood from softwood species. This method is also used for producing veneer from some hardwood species.

Slicing

Slicing is used to produce decorative veneers. There are various methods of veneer slicing such as quarter cut, crown cut, half-round and rift cut.

Quarter cut

Quarter cut

The quarter log or flitch is mounted on a metal frame so that the growth rings of the flitch strike the knife at approximately right angles, producing a series of stripes, straight in some timbers or varied in others. This cut requires the largest diameter logs, usually from tropical species. In this method, the average inclination of the growth rings to the wide surface is greater than 45 degrees.

Crown cut or flat cut

Crown cut or flat cut

The half log or flitch, is mounted on a metal frame with the heart side flat against the guide plate. The frame moves up and down against a knife in a straight plane parallel to a line through the centre of the flitch.

As each slice of veneer is removed from the flitch, the knife moves forward the same distance as the thickness of the veneer that is removed. This is repeated until the entire flitch is converted into veneer. As the veneer is removed from the flitch, it is kept in the same sequence, and the flitch is literally re-built in veneer form. This is important for its future use. The grain pattern gradually changes from one piece to the next and follows the grain of the log as it changes.

This cut of veneer is ideally suited for wall panels and furniture because of the consistency in its grain and the ability to match sequences of leaves in “book- and end-matches”. In Australia, an equivalent term “back-sawn” is used for solid timber cut in such a way that wide surface of the board is a tangential plane to the growth rings.

Half-Round Slicing

Half-Round

This method is a variation of rotary cutting. Segments or flitches of the log are mounted offcentre in the lathe and then rotated against a knife and a pressure bar. This results in the veneer being cut in a curved manner slightly across the annual growth rings. The veneer visually shows modified characteristics of both rotary and flat sliced methods.

This method produces a wider sheet of veneer from a given size of log compared to a flatslicing method. As a result, smaller logs can be used for veneer production. This technique is ideally suited for the production of veneer from plantation logs of a relatively young age and smaller diameters.

Rift-Cut Slicing

Rift-Cut

Rift cut veneer is produced in the various species of oak. Oak has medullary ray cells, which radiate from the centre of the log like curved spokes of a wheel. The rift or comb grain effect is obtained by cutting at an angle of about 15 degrees off the quartered position to avoid the flake figure of the medullary rays.

Veneer joining

Veneer leaves need to be joined together to form a “layon” in order to create the width necessary to cover the surface of substrate material which is to be veneered. Jointed veneer leaves should be suitably matched for figure and colour according to purchaser requirement.

Veneer matching

Matching is the term used to describe the method by which the individual leaves are jointed edge to edge into a layon. The method of match determines the final appearance of the panel. Careful choice of veneer colour and grain pattern may produce highly decorative effects. There are several methods of veneer matching, which are described below.

Book matching

Book matching

This method is based on the mirror image principle. To produce this image successive veneer leaves in a flitch are turned over like the pages in a book, and edge-joined in this manner. Since the reverse side of one leaf is the mirror image of the succeeding leaf, the result is a series of pairs. Book matching may be used with plain, quarter or rift sliced veneers.

When two sheets of veneer are book-matched, the "tight" and "loose" faces alternate in adjacent leaves. They reflect light and accept stain differently, and this may result in a noticeable colour variation in some species, which is often called a “picket fence” effect in Australia or a “barber pole effect” in America.

A book-match is commonly seen on furniture where veneer with a strong figure, such as swirl mahogany or walnut is used. This creates a dramatic visual effect on a cupboard door or tabletop.

Slip matching

Slip matching

Successive veneer leaves in a flitch are “slipped’ one alongside the other and edgeglued in this manner. The result is a series of grain repeats, but no pairs. The danger with this method derives from the fact that grain patterns are rarely perfectly straight. Where a particular grain pattern “runs off” the edge of the leaf, a series of leaves with this condition could visually make a panel “lean”. This method gives the veneer layon the uniformity of colour because all faces have the same light refraction. This is in contrast to book matching where alternating leaves are turned over.

Reverse slip matching

Reverse slip matching

This method is generally used with crown cut veneers. Veneer leaves are slip matched, then every second leaf is turned end to end. The method is used to balance crowns in the leaves so that not all the crowns appear at one end.

Random matching

Random matching

In this method individual leaves are random matched with the intention of dispersing characteristics such as knots or gum veins more evenly across the sheet. The advantage of random matching is that veneers from several logs may be used in the manufacture of a set of panels.

Herringbone matching

Herringbone matching

Veneer strips are used and matched to both sides of a centre line, at an angle to it. The resulting appearance is reminiscent of the bones in a fish as they are attached to the backbone.

Diamond and reverse diamond matching

Diamond and reverse diamond matching

Diamond matching is a variation of quarter matching which can be used to advantage when the veneer is straight grained with not too much figure. The sheets are cut on an angle and quarter-matched to produce a diamond figure. Reverse diamond matching uses the same principle with the same kind of veneers, but the grains are matched to produce an “X” pattern rather than a closed diamond.

The above methods are frequently used for matching veneers. However, other individually designed matching methods can be used to develop beautiful unique patterns by utilizing exquisite patterns and colours of veneers.

Inlay

Cabinetmakers often frame a highly decorative wood grain with a plainer grain to accent it. To delineate it, a narrow strip or dark or patterned veneer is cut in along the joint line. This technique is called inlay. It has also come to mean cutting patterns into the basic veneer as well.

Marquetry

Veneer faces of various kinds are made up with small segments of veneer cut into patterns and fitted together. Often many different species and grain patterns, including many of the most exotic grains, are used in the marquetry work. Beautiful effects can be obtained using the marquetry technique It is generally applied in furniture manufacture and can be quite ornate.

Balanced construction

A construction such that forces induced by uniformly distributed changes in moisture will not cause warpage. In veneered panels, a construction in which back and face veneers are essentially equal in thickness, grain direction and properties is normally balanced construction.

Balance match

One or more pieces of uniform size used in a single face.

Bird’s eye

A figure created by local sharp depressions in the annual rings accompanied by considerable fibre distortions.

Blister

Spot or area where veneer does not adhere. Blisters are considered a bond line failure.

Book match

Adjacent sheets from a flitch, opened like a book, with the figure on the back of the first sheet matched to the figure on the face of the next sheet. The fibres of the wood, slanting in opposite directions in the two sheets, create a characteristic light and dark effect when the surface is seen from an angle.

Burl (burr)

A hard, woody, abnormal growth or excrescence on trunk or branch formed by the local development of numerous dormant buds and often caused by injury to the tree.

Burl figure

A localised distortion of the grain generally rounded in outline. Frequently includes one or more clusters of several small adjoining conical protuberances, each usually having a core or pith, but no appreciable end grain.

Centre match

An even number of pieces of equal size matched with a joint formed in the centre of the panel.

Seasoning checks

Small slits running parallel to the grain of wood, caused chiefly by strains produced in seasoning.

Peeler or slicer checks

Closely spaced checks originating from one side of a veneer, usually the surface nearest the pith of the tree. Caused by stressing during veneer cutting (peeling or slicing).

Compression wood

Abnormal wood that can occur in non-pored timbers, characterized anatomically by short thick-walled cells showing spiral markings. The wood is denser, more brittle and prone to greater longitudinal shrinkage than normal wood.

Continuous match

Each panel face is arranged from as many veneer sheets as necessary for the specified panel width. If a portion of a veneer is left over, it becomes the start of the next panel face.

Core

The inner part of a veneered panel or plywood between face and back. Particleboard, MDF, sawn timber, hardboard, veneers or other material can be used as cores.

Cross-banded

A veneered panel in which the grain direction of the veneers is parallel to the shorter panel dimension.

Crotchwood

Crotchwood comes from the portion of a tree just below the point where it forks into two limbs. The grain is crushed and twisted, creating a variety of plume and flame figures, often resembling a well-formed feather. The outside of the block produces a swirl figure that changes to full crotch figure as the cutting approaches the centre of the block.

Crown cut

Sliced from a billet with successive veneers parallel to the axis of the billet and kept in sequence as cutting progresses across the diameter (see Figure 3). This method is also known as Flat Cut. In Australia, an equivalent term “back-sawn” is used for solid timber cut in such a way that the wide surface of the board is a tangential plane to the growth rings.

Curly

Figure which occurs when the fibres are distorted producing a wavy or curly effect in the veneer. Primarily found in North American maple and birch.

Defect, open

Open checks, splits, joints, knotholes, cracks, loose knots, gaps, voids or other openings interrupting the smooth continuity of the wood surface.

Discolouration

Stains in wood substances. Common veneer stains are sap stains, blue stains, stains produced by chemical action caused by iron in the cutting knife coming into contact with the tannic acid of the wood, chemical reaction between extractives in wood and glue or finish.

End match or Butt

Veneers as described for book matched, but the ends of the sheets are also matched.

Extractives

Many species have a high tannin content, which reacts with iron to form black and insoluble iron tannates if the wood is in a wet or humid conditions. Any contact with iron can cause problems, therefore it is essential that special care be taken during storage and manufacture of these types of veneers, veneered panels and products. All external fixings and metal joints should be of heavily galvanised steel or of non-ferrous metals.

Face veneer

Better quality veneers used to cover the visible surfaces of a panel.

Figure

The pattern produced in a wood surface by annual growth rings, rays, knots, deviations from natural grain, such as interlocked and wavy grain, and irregular colouration.

Fiddle-back figure

A fine, strong, even, ripple figure in veneers. The figure is often found in red gum, myrtle, mahogany and maple, but also occurs in other species.

Flitch

A section of log made ready for slicing into veneers, or the bundle of sliced veneers.

Grain

The direction, size, arrangement and appearance of the fibres in timber and veneer.

Grain slope

Expression of the angle of the grain to the long edges or the length of the veneer.

Gum pockets

Well defined openings between rings of annual growth containing gum or evidence of prior gum accumulations.

Gum veins

A ribbon of resin between growth rings − a common feature of eucalypts. Gum forms as a protective response to injury to the tree, such as from insect attack, fire or mechanical damage.

Half-round veneer

Veneer produced in the same manner as rotary cutting, except that the piece being cut is secured to a “stay log”, a device that permits the cutting of the log on a wider sweep than when mounted with its centre secured in the lathe. A type of half-round cutting can be used to achieve “flat cut” veneer.

Hardwood

Lumber or veneer produced from broad-leafed or deciduous trees in contrast to softwood, which is produced from evergreen or coniferous trees.

Heartwood

The non-active centre of a tree, generally distinguishable from the outer portion (sapwood) by its darker colour.

Interlocked grain

The angle of the fibres periodically changes or reverses in successive layers.

Joint

The line between the edges or ends of two adjacent sheets of veneer in the same plane.

Joint, edge

Joint running parallel to the grain of the veneer or lumber.

Joint, open

Joint in which two adjacent pieces of veneer do not fit tightly together.

Knife marks

A raised or hollowed cross grain cut caused generally by a nick in the peeling or slicing knife.

Knot

A portion of a branch, which is enclosed by the natural growth of the tree, with grains usually running at right angles to that of the piece of wood in which it occurs.

Knot, open

Opening produced when a portion of the wood substance of a knot has dropped out, or where cross checks have occurred to produce an opening.

Loose side of veneer

In knife-cut veneer, that side of the sheet that was in contact with the knife as the sheet was being cut, and containing cutting checks (lathe checks) as a result of bending of the veneer at the knife edge.

Moisture content

The weight of the moisture in wood, expressed as a percentage of its ovendry weight.

Overlap

A condition in which one piece of veneer overlaps an adjacent piece of the same ply.

Quarter-cut

A method of slicing veneers whereby the average inclination of the growth rings to the wide surface is greater than 45 degrees (see Figure 2).

Quilted figure

Although greatly resembling a larger and exaggerated version of pommele or blister figure, quilted figure has bulges that are elongated and closely crowded. Quilted grain looks three-dimensional when seen at its best and is most commonly found in mahogany, maple, sapele and myrtle. It occurs only rarely in other species.

Pommele

This figure resembles a puddle surface during a light rain − a dense pattern of small rings enveloping one another. Some say it has a "suede" or "furry" look. It is usually found in extremely large trees of African species, such as sapele, bubinga and makore. Some domestic species with a sparser, larger figure are referred to as "blistered".

Ribbon grain

The ribbon effect produced by quarter slicing woods with interlocking grain.

Rift cut veneer

A variation on the quarter cut appearance specifically used to eliminate medullary rays in white oak, which results in a broader stripe. Veneer is produced by centring the entire log in a lathe and turning it against a broad cutting knife set into the log at a slight angle (Fig 5).

Rotary veneer

A veneer produced when a log mounted in a lathe is rotated against a cutting blade. This method of peeling is used to produce veneers for plywood manufacture.

Rough cut

Irregular shaped areas of generally uneven corrugation on the surface of veneer, differing from surrounding smooth veneer and occurring as the veneer is cut by the lathe or slicer.

Rubber marks

A raised or hollowed cross grain cut caused by a sliver between the knife and pressure bar.

Sapwood

The living wood occurring in the outer portion of a tree immediately under the bark. Sometimes referred to as “sap”. Generally, it is lighter in colour than the heartwood, the part of the tree used for veneer.

Sliced veneer

Veneer produced by thrusting a log or sawn flitch into a slicing machine, which shears off the veneer in sheets.

Slip match

The top sheet of veneer is slid into position with the sheet beneath it. The face of both sheets are exposed, instead of the back of one sheet and the face of another, as in book matching.

Smooth, tight cut

Veneer carefully cut to minimize peeler or slicer checks.

Softwood

General term used to describe lumber or veneer produced from needle and/or cone bearing trees.

Species

A distinct kind of wood.

Spiral grain

The fibres form a spiral around the circumference of the tree.

Splits

Separation of wood fibre running parallel to the grain.

Telegraphing

Visible irregularities in the surface of the face of the veneered panel or plywood caused by corresponding irregularities in the underlying core such as voids, zigzag stitches etc.

Tension wood

Reaction wood formed typically on the upper sides of branches and leaning or crooked boles of hardwood trees. Characterized anatomically by little or no lignification and by presence of an internal gelatinous layer in the fibres. It has an abnormally high longitudinal shrinkage, tending to cause warping and splitting, and the machined surface tends to be fibrous or woolly especially when green.

Tight side

In knife-cut veneer, the side of the sheet farthest from the knife as the sheet is being cut and containing no cutting checks (lathe checks).

Wavy grain

The fibres form short undulating waves in a regular sequence.