Grade classification of oak furniture panels allows the customer to define the wood quality level and characteristics of the presented wood defects (if available). To find out more details on this issue, first of all it is necessary to understand what wood defects it is referred to. Let’s consider the most common thereof.
POSSIBLE WOOD FLAWS IN OAK FURNITURE PANELS
- Presence of knots. To assess the grade of wood it is necessary to estimate the number of knots and their size, as well as their appearance and intergrowth. Knots tend to fall out, that damages the structure and appearance of the material. Furthermore, the presence of knots complicates the processing of wood and affects its strength properties.
- Cracks. To determine the wood grade, sizes of cracks and their location should be taken into account. Usually, the presence of such defect is due to the violation of the drying technology.
- Fibres. Specialists assess the direction of the wood fibers and their location (insofar they deviate from the straight line). Inclination of fibres influencing the wood durability and strength usually depends on growth conditions of a tree. At the same time, the deviation of fibres from a straight line in most cases is the result of warping and shrinkage.
- Heartwood. Depending on the condition, the heartwood could complicate processing of the finished product or cause its cracking. In addition, the heartwood has generally a different color shade.
- Sapwood. Experts call so young layers of wood, which can reduce its strength due to the high water content. They also differ from the main trunk in color and may be affected by fungi or insects.
- Biological contamination (in particular, rotting). This effect is usually caused by fungi that destroy wood. To prevent rotting of wood, it is important to carefully monitor its insulation from moisture. To determine the wood grade, the presence of biological contamination, its extend or the total absence of decay is primarily evaluated.
- Deformations. Specialists determine the presence of deformations, their properties and size. Typically, the deformations that complicate the processing of wood arise from technology violations in the manufacture of furniture panels
There are also a number of defects that could affect the grade of wood. For example, inbark, false hearts, dual heartwoods, water heart and others.
CHARACTERISTICS OF CERTAIN TYPES OF WOOD DEPENDING ON GRADE
There are two types of furniture panels marked according to the grades of each side of the product: edge-glued and finger-joint furniture panels. Each of them bears marks AA, AB or BB – depending on the grades of sides of the finished product. In case a furniture panel is finger-joint, the marking begins with letter C.
1. Edge-glued furniture panels:
- AA Grade. Lamellas are selected for maximal matching in color, saw cut and nature of the texture. Any defects are not acceptable.
- AB Grade. In contrast with AA grade, the other side may have sapwood as well as sound light tight intergrown knots up to 5 mm.
- BB Grade. Lamellas are not selected by color and texture, the nature of cutting is only acceptable. Sound light and tight intergrown knots up to 5 mm and brown staining are allowed on one of the panels sides. The other side may have brown staining without any other flaws.
- BC Grade. Lamellas are not selected according to grain or texture, significant differences in color shades are allowed. There may be some defects which do not affect either the aesthetics or the performance characteristics. For example, the presence of sapwood and knots of up to 30 mm are considered acceptable.
2. Finger-joint furniture panels:
- AA Grade. Lamellas may be of various grains, color und cut. However, absence of defects on both sides is of crucial importance.
- AB Grade. No color, grain or cut type matching. One side may not have any flaws, and on the other side sapwood as well as sound light well intergrown knots up to 5 mm are allowed.
- BB Grade. Joining and gluing is carried out without color and cut scheme. One side may have brown stains and significant contrast color change. The other surface may have sound light tight knots up to 5 mm in size in combination with contrast color changes and sapwood.
- BC Grade. Wood color variations, texture and grain are ignored for the C grade panel. Lamellas may have such defects as sapwood or knots (which size does not exceed 30 mm). At the same time these (or other minor) defects should not adversely reflect on the quality of the material or its operational characteristics.