Wood & Veneer

Chabros is considered as a trademark in the region, as its product lines of Veneer & Wood range from standard to the exotic from Different origins around the globe. Throughout its affiliates all over the world, Chabros procures raw material of high standards and qualities to meet the demands of its clients.

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Please find below some useful information about Wood & Veneer.

ANATOMY OF THE TREE

Trees have the longest lifespan of all higher forms of life. The oldest survivor is the Bristlecone pine (Pinus longeava), which grows in the White Mountains of California; it is 5,000 years old. Conifer trees, which we call softwoods emerged 725 million years ago, eventually covering two-thirds of the earth’s surface. These magnificent evergreens towered above other land plants for a further 90 million years before the first birds, snakes and dinosaurs appeared. The Angiospermae, which we call hardwoods, are the broad-leaved, flowering and fruit-bearing trees which first emerged about 140 million years after the conifers.

Upheaval of the earth’s crust, and subsequent severe climatic changes, drastically reduced them and extensive treeless savannah plains and prairies took their place.

Today, the evergreen conifers form large forests in the cool northern regions, including fir, spruce, larch, cedar yew, and the true pines.

SOFTWOODS AND HARDWOODS

These names refer to structural differences, not ones of softness and hardness. Some hardwoods, such as balsa and poplar, are much softer than botanical softwoods like yew or pitch pine. Gymnospermae – the softwoods – are naked seeded trees, which means the seeds are not enclosed in a pod. They are cone-bearing, with evergreen needles or scale-like leaves, and grow in the cool temperate northern regions. Conifers supply the bulk of the world’s commercial timber.

The hardwoods – Angiospermae – hide their seeds in fruit seed cases. These broad-leaved trees produce fruits and flowers and are deciduous, which means in temperate zones they shed their leaves every autumn.

There are two kinds of hardwood: those that carry their seeds in single-lobe cases, such as the palm tree, are called monocotyledoneae, those whose seeds cases have two lobes are dicotyledoneae. The majority of our valuable commercial hardwood come from this latter group.

The dicotyledoneae also sub-divide into two types. Polypetalous species possess both a calyx and a multi-petalled corolla, and produce beautiful flowers and fruits. Apple, among, pear, peach, and cherry are polypetalous, as are horse chestnut, maple and mahogany. Those in the apetalous group have inconspicuous flowers, lack the corolla and often the calyx, but they are strongest and most durable woods.

Timbers such as hickory, birch, alder, beech, oak, elm and walnut comes from apetalous trees.

WOOD

SELECTING WOOD

SELECTING WOOD
Timber suppliers, usually stock the softwoods most commonly used for carpentry and joinery – spruce, fir and pine. They are generally sold as dimension stock or dressed stock, the trade terms for sawn or surface-planed sections cut to standard sizes. One or more faces may be surfaced.

Most hardwoods are sold as boards of random width and length, although some species can be bought as dimension stock. Dimension timber is sold in 300mm or 1ft units.

Whichever system you use, you always allow extra length for waste and selection. When working out your timber requirements, remember that planning removes at least 3mm (3/16in) from each face of the wood, making the actual width and thickness less than the nominal (sawn) size quoted by the merchant. The length, however, is always as quoted.

Grading wood

Grading wood

Softwoods are graded for evenness of grain and the amount of allowable defects, such as knots. For general woodworking, the ‘appearance’ and ‘non-stress’ grades are probably the most useful. Stress-graded softwoods are rated for structural use where strength is important. The trade term ‘clear timber’ is used for knot-free or defectfree wood, but is not usually available from suppliers unless specified.

Hardwoods are graded by the area of defect-free wood – the greater the are, the higher grade. The most suitable grades for general woodworking are ‘firsts’ and FAS (‘firsts and seconds’).

Although specialists firms supply wood by mail order, personal selection is the best option. Take a block plane with you when buying timber, so you can expose a small area of wood to check color and grain.

MOVEMENT, MOISTURE AND SEASONING

MOVEMENT, MOISTURE AND SEASONING

Timber is hygroscopic; it picks up and releases moisture. While water is evaporating and from the center of the cells, no change in dimension is noticeable, but once the moisture content (MC) goes below about 30% – fibre saturation point – water is leaving the cell walls, which means that they will shrink and come closer together. They do not reduce significantly in length however, which accounts for the fact that timber movement is measurable across the grain, and negligible along it.

Solid wooden furniture will always move according to season and atmosphere – centrally heated homes cause problems for antiques and construction and finishing should take these vagaries into account. But this distortion is a matter of concern while wood is ‘seasoning’ – drying – as well as the effect it may have on a wooden structure or one which incorporates wood. There are differentials in drying rates and amounts within the wood itself; denser latewood with thicker cell walls shrinks proportionately more than thin-walled early wood, for instance, and pronounced radial cell systems such as the rays in oak serve to inhibit radial shrinkage, while tangential distortion continues apace. A square section of timber will become rhomboid while drying, flat – sawn boards cup away from the tree’s heart, and quarter-sawn boards (radially cut) shrink most evenly.

Such differentials cause enormous stresses inside the wood, and it is practically impossible to season a log in the round without at least a radial shake or split across the rings and along the grain. Ring or cup shakes, which follow the rings, and heart shake, which occurs in the centre of the log, are also likely. To minimize these distorting forces, the tree is converted before seasoning.
No-one who uses solid timber in a professional capacity should be without a moisture meter. Simply pressing two needles into the surface of the timber and then pushing a button enables the moisture content to be read directly from a scale. An average of 10% plus or minus 2% (for some species a slightly higher percentage is not a problem) would be appropriate for joinery in a continuous 20-24 centigrade (70-75 F) environment – the warmest likely for a home or office. Even when the timber is to be used in a more humid situation, such as a kitchen or bathroom, it may well be subject to a period of storage or display in warm dry shops or showrooms, and so should be dried to these levels.

KILN DRYING

KILN DRYING

While most kiln drying of timber is carried out in bulk by professional timber dryers, since the method involves the use of expensive and sophisticated equipment, there are smaller workshop-sized methods which involves temperature-controlled de-humidification. The timber is stacked, each layer separated by smaller pieces of dry, clean softwood placed at regular intervals to support the timber and help prevent distortion. This is known as ‘sticking’ and enables air to flow all around the timber.

The stacks are then placed in the kilns, which are sealed units within which both temperature and humidity levels can be controlled. These may vary according to the species and size of stack being dried. The choice of drying schedule – the combination of temperature, humidity and duration of kilning – is an important factor in ensuring the quality and cost-effectiveness of each batch. Too fast can be as bad as too slow.

Throughout the drying process, the timber in the kiln is checked at regular intervals to ensure that all is going smoothly and to avoid any possible degrade, such as splitting and case-hardening, where the outer surface of the timber dries too quickly in relation to its centre.

CONVERTING WOOD

CONVERTING WOOD

Although it can take many years for a tree to grow to a commercially viable size, modern forestry methods can cut down, top and debark a straight-growing tress, such as pine, in a matter of minutes. In addition, the laborious task of sawing logs into boards or beams by hand in a saw-pit has been superseded: today milling is a highly mechanized process, where logs are converted into sawn timber by a computer-controlled bandsaws or circular saws.

Milling Timber

Milling Timber
Most usable commercial wood comes from the trunk of the tree. Although larger limbs can be cut into logs, asymmetric growth rings in branches or slanted trunks usually produce ‘reaction wood’, which is unstable and warps and splits easily.

In softwood the annual-ring growth is mainly on the underside of the branch and produces ‘compression wood’; in hardwoods, the growth is mainly on the upper side and is called ‘tension wood’. Good quality felled trees are cut into logs or butts and transported to local sawmills for conversion into rough-sawn timber. Top-quality hardwood logs with large even boles fetch high prices and are usually converted into veneer. Tree trimmings and subgrade wood are generally used for manufactured boards and paper products.

Types of cut

Types of cut

The main cuts produced by modern machine methods are ‘plain-sawn’ and‘quarter-sawn’. Plain-sawn boards are cut at a tangent to the annual-growth rings, to display a decorative and distinctive elliptical figure. Quarter-sawing reveals a straight figure that is sometimes, in hardwoods such as oak, crossed with a ribbon-like ‘flake’ figure.
Different terms are used for boards within the two categories. Plain-sawn timber is also known as flat-sawn, flatgrain or slash-sawn timber. Quartersawn timber includes rift-sawn, combgrain, edge-grain and vertical-grain.

Plain-sawn boards in Britain and elsewhere in Europe have growth rings meeting the face of the board at an angle of less than 45 degrees. In quarter-sawn boards, the angle of growth rings to the face of the board is greater than 45 degrees. Plain-sawn boards in North American have growth rings meeting the face at an angle of less than 30 degrees.

Boards where the rings meet at an angle between 30 and 60 degrees are called riftsawn; these boards display straight figure with some ray-cell patterning and are sometimes referred to as comb grain. True quarter-sawn boards are cur radially, with the annual rings perpendicular to the board’s face, but in practice boards with the rings at an angle of not less than 60 degrees are classified as quarter-sawn.

Converting a log
The stability and figure of wood are determined by the relationship of the plane of the sawcut to the annual-growth rings. The most economical method of converting a log is to cut it ‘through and through’ (1). In this process, parallel cuts are mad through the length of the log to produce plain-sawn, rift-sawn and a few quarter-sawn boards.

Plain-sawn logs (2) are partly cut through and through, producing a mixture of plain-sawn and rift-sawn boards. There are number of ways to cut a log so that it produces quarter-sawn boards. The ideal method is to cut each board parallel with the rays, like radiating spokes of a wheel, but this is wasteful of timber and is not used commercially.

The usual method is to cut the log into quarters and convert each quadrant into boards (3). Commercial quarter-sawing first cuts the log into thick sections and then into quartered boards (4).

Of all the cutting methods, quarter sawing produces boards that are the most stable, but this exacts a price. Quarter sawing is the most wasteful way to cut a log, it’s time consuming, expensive and you need a larger log to produce reasonably wide boards.

 

VENEER

ALL ABOUT VENEER

ALL ABOUT VENEER

Veneers are very thin sheets or ‘leaves” of wood that are cut from a log for construction or decorative purposes. Whether selected for their natural colour and figure or worked into formal patterns, veneers bring a unique quality to furniture and woodware. With the widespread use of stable man-made boards for groundwork and the development of modern adhesives, today’s veneered products are superior to solid wood for certain applications.
Veneering has been a method of maximizing the use of rare, exotic and expensive timber from as early as pre-Egyptian times. Until comparatively recently, saw-cutting was the only method of producing the leaves, which would usually be as thick as 3mm (1/8 in). With sophisticated modern production methods, thickness can be brought down to as little as 0.6mm which is the Euro/ American Standard (thinner is possible but is not practical/recommended for face applications), which obviously achieves great efficiency in terms of area covered.

For straight forward decorative purposes, veneers also have a conservation side-effect in that timber species under threat of extinction can be made to last far longer. For the exporting country, veneer production means work for local labour, added value and a higher return on an indigenous resource. For the individual furniture maker, the relative cheapness of the material makes it attractive, an advantage with especially exotic timbers, but veneering is a labour-intensive craft. Such economics make huge sense in large-scale manufacturing, where mechanized application processes virtually eliminate the need for highly skilled craftspeople.

Constructional veneers go into the production of plywood, blockboard, and other laminated timber products, but appearance is not the main criterion in such uses, and manufactured boards do not depend on valuable woods, other than visual selection for the facing plys, which are better quality than the internal ones. There is, however, a high demand for pre-veneered boards, which are faced with high value and exotic timbers.

Used in furniture and paneling, they combine the advantages of beautiful hardwoods with the structural stability and comparative cheapness of sheet material. The wonderful figuring of truly decorative veneers is a quality for which the best logs of a batch are often earmarked. Other characteristic, which would be considered defects in a log for conversion into timber, can make veneer yet more highly prized; colour variation, growth irregularities, even diseases, can be turned to advantage. Burrs, birds’eye and crotch timber – from the junction between branch and trunk – would make no sense in a structural component, but a great one in decorative face applications. Such effects are best exploited on flat cut veneer, which is made by slicing a square-cut baulk, first softened with steam or hot water. The block is mounted on a carriage which carries it against a large blade and pressure plate, much like the mouth of a giant plane, thickness by thickness. This flat – cut method produces a figure exactly like that of an ordinary board, with the visual advantage that the pattern repeats from sheet to sheet. Thence comes the traditional ‘book matching’, where consecutive leaves can be laid on, say, a pair of doors to give a mirror – image effect.

The knife and pressure plate is also used in the various forms of rotary veneer production’ a log mounted eccentrically and turned against the blade will produce an unusual decorative face pattern unobtainable in any form of board, while constructional veneers for ply are rotary cut from a centrally mounted log. This is more economic because the sheet is continuous. Builder’s constructional plywood (’shuttering’) made from veneers cut in this way, exhibits the strange characteristic of repeating flaws, like a wallpaper= pattern.

VENEER PRODUCTION

VENEER PRODUCTION

Highly sophisticated production techniques are used to satisfy the growing demand for veneer. Every stage in the manufacture of veneer requires specialist knowledge.

Choosing Logs
The process starts with the log buyer, who must have the skill and experience to assess the condition and commercial viability for veneer within a log, basing this solely on an external examination. By looking at the end of the log, the buyer has to determine the quality of the wood, the potential figure of the veneer, the colour, and ratio of sapwood to heartwood. Other factors – such as the presence and extent of staining and weaknesses or defects in the form of shakes, ingrown bark, excessive knots or resin ducts – will also affect the value or suitability of the log and must be taken into consideration. Much of this information will be revealed by the first cut through the length of the log – but the log must be purchased before this cut can be made.

Treating Logs

Before they are converted into veneer, logs are softened, either by immersion in hot water or by being steamed. Depending on the cutting method, the log may be treated whole or it may first cut into flitches by a huge bandsaw. The time taken for this softening is controlled by the type and hardness of the wood and the thickness of the veneer to be cut. The process can take days or weeks. Some pale woods, such as maple and sycamore, are not pretreated because the softening process would discolour the veneer.

Cutting Veneer
Another skilled production expert in the veneer cutter, who decides the best way to convert the log so that it will provide the maximum number of high-quality leaves. Most veneer logs are cut from the main stem of the tree between the root butt and the first branch.

The bark is removed and the log is checked for foreign matter, such as nails or wire. As soon as decorative veneers are cut, they are taken from the slicer and stacked in sequence. This stack, or set, then passes through a machine drying process before being graded.

Although most species are clipped on a guillotine to trim them to regular shapes and sizes, others, such as yew or burr veneer, are kept as when cut from the log.

Grading decorative veneer
Veneers are inspected for natural or milling defects, thickness, colour and type of figure, then graded and priced according to their size and quality. The veneers from a log may vary in value: better or wider ones, graded as face quality, have a higher value than the narrower or poorer backing quality (also known as balancing veneer). The veneers are kept in multiples of four for matching purposes and bound into bundles of 16, 24, 28 or 32 leaves. The bundles are then stacked in the order they were sliced from the log, and stored in a cool warehouse, ready for sale.

VENEER CUTTING METHODS

VENEER CUTTING METHODS
Plain Slicing – Flat Cutting :
This method of cutting produces what’s known as “cathedral” grain effect or “crown cut”.

Quarter Slicing :

Quarter Slicing a log results in straight uniform grain known as “quarter cut”. One-fourth of a log is brought down against a stationary knife to slice pieces perpendicular to the annual growth rings. In some species like white oak, red oak, cherry and sycamore, this produces a distinct ray fleck or silver grain pattern (flakes).

Rotary Slicing :
Rotary – Sliced veneer can be sufficiently wide to provide a full sheet or a one-piece face. This method is used mostly in birch ply production.

Half – Round Slicing :
The motion in half – round slicing basically is a combination of rotary and plain slicing. The resulting veneer is similar to plain slicing except that the “cathedral” patterns have more rounded tops.

Back Cutting
(Back Half-Round) :
Half-round logs are mounted on a stay-log with the heartwood facing outwards. This method is used for cutting the decoratively figured butts and curls.

TYPES OF VENEER

TYPES OF VENEER

Veneer figure derives both from the wood’s natural features and from where and how it is cut. The description can refer to the method of cutting, such as ‘crown-cut’; or to the part of the tree from which the veneer comes, as in ‘burr’ veneer.

Buying Veneer
Each veneer is unique and unlikely to be matched from other bundles, so a generous allowance for wastage should be made when the area needed for a project is calculated. Leaves are traditionally price by the square root, although the thickness may be given in metric measurements. Some merchants supply pre-cut lengths at a set price per piece.

For matching purposes, veneers are almost always kept in the order they were sliced from the log, so leaves and bundles are taken from the top of the stack. Suppliers do not normally pull out selected leaves, as doing so reduces the value of the veneer flitch.

Mail-order veneer

Full veneer supplied by mail orders is usually rolled for dispatch. Smaller pieces, such as burrs, or curls, may be flat packed; if they are sent with a package of rolled veneer, they maybe dampened to allow them to bend without breaking. A rolled package should be opened carefully, to prevent it in springing open and damaging the fragile veneer inside. End splits, particularly on light-coloured woods, must be repaired promptly with gummed paper tape, to prevent dirt getting into the split. Veneer that is still curled after being unpacked can be either dampened with steam from a kettle or passed through a tray of water, and then pressed flat between sheets of chipboard. Damp veneer left between boards may develop mildew.

Because wood is light-sensitive and can lighten or darken (according to species), veneers should be stored flat and protected from dust and strong light.

It’s essential when supplying wood by mail order to have trust in your specialist wood supply firm to guarantee maximum output of communication and in result maximum return of supply.

BURR OR BURL VENEER
Burr or burls are abnormal growth on tree trunks. The fragile veneers cut from them display an attractive pattern of tightly packed bud formations that appear as rings and dots. Burr veneer is highly priced for furniture, turnery and woodware, and is therefore relatively expensive. It is supplied in irregular shapes in various sizes.

BUTT VENEER
Butt veneers are cut from butts (stumps). Half round cutting on a rotary lathe produces highly figured veneers caused by distorted grain. These are fragile veneers, and may have holes where small pieces have become detached. To repair very small holes, matching filler can be applied after the veneer is laid.

CROWN-CUT VENEER
Tangentially cut flat-sliced veneers are known as ‘crown-cut’. They have an attractive figure of bold sweeping curves and ovals along the center of the leaf, with striped grain nearer the edges. They are used for furniture-making and interior wall paneling.

CURLY-FIGURED VENEER
FIGURED OR FIDDLEBACK VENEER
Wavy-grained woods produce curly-figured veneers, with bands of light and dark grain running across the width of the leaf. ‘Fiddleback’ sycamore and ripple ash are typical examples: the former gets its name from its use in making violin backs. Curly-figured veneer is employed to give a distinctive horizontal decorative effect – for instance, on cabinet doors and panels.

CURL/CROTCH VENEER
When the ‘crotch’ or fork of a tree, where the trunk divides, is cut perpendicularly, an attractive ‘curl figure’ is revealed. The distorted diverging grain of the wood produces a lustrous upward sweeping plume pattern known as ‘feather figure’, often used on panelled cabinet doors.

FREAK-FIGURED VENEER
Veneers displaying various unusual patterns are rotary-cut from hardwood logs with irregular growth. Bird’s-eye maple and masur birch are well-known examples of such freak-figured veneers. The distinctive brown marks of masur birch are caused by woodboring larvae that attack the cambium layer of the growing tree. Woods with irregular grain also produce veneers with ‘blistered’ and ‘quilted’ figures.

RAY-FIGURED VENEER
When quarter-cut, woods that have a pronounce ray-cell structure, such as oak and plane, display striking figure. Quarter-cut plane veneer, with speckled or fine-wavy grain figure, is known as lacewood. Distinctive wide ray cells in oak produce ‘ray-fleck’ or ‘splash’ figure, long in demand for furniture-making and paneling.

STRIPED OR RIBBON VENEER
Where the radial cut is taken across the width of the growth rings, quarter-cut veneers usually display a striped or ‘ribbon’ figure. On woods that grow with interlocked reverse-spiral grain, the stripes appear to change from light to dark, depending on the degree of reflectivity of the cells (end-on cells absorb light) and the angle from which they are viewed.

COLOURED VENEER
Specialist veneer suppliers sell artificially coloured veneers made from light-coloured woods such as sycamore and poplar. ‘Harewood’ is sycamore that has been treated chemically, turning it silver grey to dark grey. Other colours are produced by pressure-treating dyed veneers to achieve maximum penetration of the dye.

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