Veneer
| Infobox on Veneer | |
|---|---|
| Example of Veneer |  |
| Facts | |
| Origin | - |
| Stowage factor (in m3/t) | - |
| Humidity / moisture | 10 - 15% |
| Ventilation | - |
| Risk factors | See text |
Veneer
Description
In woodworking, veneer refers to thin slices of wood, usually thinner than 3 mm, that are typically glued onto core panels (wood, particle board or medium-density fiberboard) to produce flat panels such as doors, tops and panels for cabinets, parquet floors and parts of furniture. They are also used in marquetry. Plywood consists of three or more layers of veneer, each glued with its grain at right angles to adjacent layers for strength. Veneer beading is a thin layer of decorative edging placed around objects, such as jewelry boxes. Veneer is also used to replace decorative papers in Wood Veneer HPL. Veneer is also a type of manufactured board.
Veneer is obtained either by "peeling" the trunk of a tree or by slicing large rectangular blocks of wood known as flitches. The appearance of the grain and figure in wood comes from slicing through the growth rings of a tree and depends upon the angle at which the wood is sliced. There are three main types of veneer-making equipment used commercially:
- A rotary lathe in which the wood is turned against a very sharp blade and peeled off in one continuous or semi-continuous roll. Rotary-cut veneer is mainly used for plywood, as the appearance is not desirable because the veneer is cut concentric to the growth rings.
- A slicing machine in which the flitch or piece of log is raised and lowered against the blade and slices of the log are made. This yields veneer that looks like sawn pieces of wood, cut across the growth rings; such veneer is referred to as "crown cut".
- A half-round lathe in which the log or piece of log can be turned and moved in such a way as to expose the most interesting parts of the grain.
Each slicing processes gives a very distinctive type of grain, depending upon the tree species. In any of the veneer-slicing methods, when the veneer is sliced, a distortion of the grain occurs. As it hits the wood, the knife blade creates a "loose" side where the cells have been opened up by the blade, and a "tight" side.
The finest and rarest logs are sent to companies that produce veneer. The advantage to this practice is twofold. First, it provides the most financial gain to the owner of the log. Secondly, and of more importance to the woodworker, it greatly expands the amount of usable wood. While a log used for solid lumber is cut into thick pieces, usually no thinner than 3 cm, veneers are cut as thin as 0.6mm. Depending on the cutting process used by the veneer manufacturer, very little wood is wasted by the saw blade thickness, known as the saw kerf. Accordingly the yield of a rare grain pattern or wood type is greatly increased, in turn placing less stress on the resource. Some manufacturers even use a very wide knife to "slice off" the thin veneer pieces. In this way, none of the wood is wasted. The slices of veneer are always kept in the order in which they are cut from the log and are often sold this way.
Types of veneer
There are a few types of veneers available, each serving a particular purpose.
- Raw veneer has no backing on it and can be used with either side facing up. It is important to note that the two sides will appear different when a finish has been applied, due to the cell structure of the wood.
- Paper backed veneer is as the name suggests, veneers that are backed with paper. The advantage to this is it is available in large sizes, or sheets, as smaller pieces are joined together prior to adding the backing. This is helpful for users that do not wish to join smaller pieces of raw veneers together. This is also helpful when veneering curves and columns as the veneer is less likely to crack.
- Phenolic backed veneer is less common and is used for composite, or manmade wood veneers. Due to concern for the natural resource, this is becoming more popular. It too has the advantage of being available in sheets, and is also less likely to crack when being used on curves.
- Laid up veneer is raw veneer that has been joined together to make larger pieces. The process is time-consuming and requires great care, but is not difficult and requires no expensive tools or machinery. Veneers can be ordered through some companies already laid up to any size, shape or design.
- Reconstituted veneer is made from fast-growing tropical species. Raw veneer is cut from a log, and dyed if necessary. Once dyed, the sheets are laminated together to form a block. The block is then sliced so that the edges of the laminated veneer become the “grain” of the reconstituted veneer.
- Wood on Wood Also called 2-ply is a decorative wood veneer face with a utility grade wood backer applied at an opposing direction to the face veneer.
There are a number of "patterns" common to veneered work. This refers to the way the veneers are laid up.
A: Book matched: where the veneers are opened from the flitch much like the pages of a book.
B: Slip matched: where the pieces are joined together in the order they come from the flitch, and have the same face kept up.
C: Radial matched: where the veneer is cut into wedge shaped pieces and joined together.
D: Diamond matched: where the pattern formed is diamond shaped.
Advantages of using veneer
Furniture made with wood veneer uses less wood than the same piece of furniture made with solid wood. Some projects built using wood veneer would not be possible to construct using solid lumber, owing to expansion and contraction caused by fluctuation of temperature and humidity.
Application
Veneer is primarily manufactured for the furniture industry. A distinction is drawn between face veneers and cross-ply veneers, depending upon their intended use. Since face veneers determine the appearance of the product, sliced and rotary cut veneers are used for this purpose. Cross-ply veneers act for example as intermediate layers in plywood in order to suppress swelling and shrinkage of the lumber.
Shipment / Storage / Risk factors
Breakage may occur due to poor packing, and is more likely in crates than in boxes. Cracks along the grain may also be caused by poor packing, but may also be caused by drying out. Care should be taken in establishing the cause. Warping can occur if moisture is absorbed, although wood that is of even growth and well cut will not normally distort on absorbing moisture. Mould damage may be the result of inherent moisture due to improper treatment. Contact with metal is liable to cause staining of the veneer with consequent loss in value.
There are three causes for waviness of veneer:
•*If the veneers are dry and also exhibit no moisture stains or rings, a production error (excessively rapid drying) may have been the cause.
- If stains and rings are visible, but the veneer is nevertheless dry and wavy, it is to be suspected that the veneer has become damp during storage and has redried.
- If the veneer is still wet and wavy, the damage may have occurred during transport or storage. In the latter case, the truck or container must have been leaky or loading was carried out in rain.
If the product is dry for shipment, ventilation is not normally required.