This is a set of characteristics that are easy to identify without violating the integrity of the lumber and which allow you to distinguish one species from another. To the main physical properties include color, texture and the smell of wood.

What does the smell of wood mean?

Each type of wood has its own unique smell. We were not mistaken - indeed, all wood has a smell. Odorless wood also has its own smell; it is simply not captured by the human sense of smell.

The smell of wood associated with the presence of tannins, resins and essential oils. The intensity and persistence of the aroma depend on their quantity.

Almost all freshly felled wood has a rich and distinct aroma, but during drying it weakens significantly or disappears altogether, for example, like teak, juniper, acacia, walnut or oak wood. The presence of a persistent odor for a long time, even after drying, not all types of wood can boast.

The smell of wood is an important physical property.

What does the smell of wood tell us:

On the belonging of lumber to a particular breed. Experienced craftsmen can accurately name the type of wood only by smell;

About the quality of wood. Wood affected by fungi or rot changes its smell, for example, the smell of pine wood when rotting, it acquires sweetish vanilla notes;

About the scope. There is wood that loses its smell after drying and no impact on the material will bring it back, but there is one that smells quite strongly after processing or begins to smell stronger under the influence of heat. Moreover, not everyone the smell of wood pleasant to humans, some breeds have a persistent pungent and unpleasant odor. Knowing all these nuances, you can choose the right material for yourself and avoid the discomfort associated with the smell of wood.

The core of wood has the most intense smell, it is in it that the maximum concentration of tannins and essential substances is found.

The smell of wood has not only distinctive, but also beneficial features. Together with fragrances environment substances with antiseptic and bactericidal properties are released, help to purify the air in the room. Therefore, in a house made of wood, it is so easy and free to breathe.

What is the smell of wood of different species

The smell of wood different breeds inimitable and unique. Some of them are typical and familiar to everyone, some are difficult to describe in words and compare with something.

All the smells of wood can be conditionally divided into pleasant and unpleasant. The wood of juniper, cypress, citrus trees, rosewood, acacia and peach has a pleasant, attractive smell for a person. But the wood of teak, laurel and poplar has a sharp and unpleasant odor. Wood has the strongest odor. conifers due to the large amount of resins in the composition. The smell of pine wood is the strongest, fragrant and fresh in intensity. In second place is juniper wood, its smell also persists for a fairly long period.

Concerning hardwood, then they smell weaker, the intensity and durability of the smell is affected by the amount of tannins in the wood. For example, scent of linden wood very resistant and remains even after drying and processing. The substance is responsible for the smell of linden. - phraseol, which is a lot in the structure of the tree. This smell is familiar to everyone - sweet with honey notes. Barrels for storing honey are made from linden wood.

The smell of oak wood sour, smells of tannins. Oak wood is well suited for the production of barrels for storing beer or cognac, the aroma of wood, mixed with alcohol, gives it a unique shade.

The smell of birch wood almost imperceptible to humans. Therefore, such wood is often used for the production of dishes or containers for storing cereals.

Irina Zheleznyak, Correspondent of the online publication "AtmWood. Wood-Industrial Bulletin"

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Each type of wood has its own specific smell. In some types of wood, it can be very weak, almost indistinguishable to humans. Smells come mainly from gums, resins, essential oils and other substances contained in wood. The core has a stronger odor, because. contains the largest amount of these substances. The smell of wood is stronger immediately after felling the tree. After drying, it becomes weaker, and in some tree species it changes altogether.

Aromas of some tree species

The strongest odor has coniferous wood containing resin. The smell of hardwood is much weaker and depends on the presence of tannins in it.
In conifers, the smell of turpentine predominates. Juniper has a pleasant, strong smell. Rosewood and backout smell like vanilla, while teak smells like rubber. Oak has the smell of tannins, while balsamic poplar and sophora kernels smell like dressed leather. Interestingly, coniferous wood affected by the fungus Trametes odorata changes its smell and smells of vanilla.

When the smell of wood matters

It is very important to take into account the smell of wood when choosing a material for decorative and artistic work, when making containers for storing and packaging food products from it. For example, it is customary to make barrels for honey from linden. For wine and beer, it is best to make barrels from Mongolian oak. Butter easily absorbs foreign odors and for its transportation over long distances, it is best to use a container made of Australian wood coniferous tree Araucaria Cunningham. It is light, dense, does not let in extraneous aromas.

PHYSICAL PROPERTIES OF WOOD

These include: appearance, smell, macrostructure indicators, humidity and related changes (shrinkage, swelling, cracking, warping), density, electrical, sound and thermal conductivity.

Appearance of wood

The appearance of wood is characterized by the following properties: color, gloss, texture and macrostructure.
1. Color of wood.
Under color woods understand a certain visual sensation, which depends mainly on the spectral composition of the light flux reflected by it. Color is one of the most important characteristics appearance wood. It is taken into account when choosing breeds for interior decoration, making furniture, musical instruments, art crafts, etc.
The wood of oak, beech, white acacia, velvet wood is distinguished by the greatest brilliance from domestic species; from foreign - satin wood and mahogany (mahogany).
Color shades of wood have a wide range. It must be remembered that the color of wood can vary not only depending on the species, but within the same species there can be several dozen variants of tonal ratios. This factor is influenced climatic conditions in which a tree grew and others natural factors. Identifying and using a color palette is a critical moment in a design quest. Coloring wood is given by coloring tannins found in its fiber. Dominated tree species with warm shades (yellow, ocher, red, red-brown, brown), but there are green, blue, purple and black woods that are considered exotic in our country.
The color shades of various species can be classified into main groups, where one color of wood will prevail:
yellow - birch, spruce, linden, aspen, hornbeam, maple, fir, ash (whitish yellow with light shades of pink and red), barberry (lemon yellow), mulberry (golden yellow), hawthorn, Karelian birch, lemon tree, acacia (sapwood), bird cherry (reddish brownish yellow), ailanthus (pinkish yellow);
brown - cedar, poplar, elm kernel (light brown), beech, larch, alder, pear, plum (reddish-pinkish-brown), chestnut, mountain ash (brown-brown), acacia (yellow-brown), Anatolian walnut ( greenish brown);
brown - cherry (yellowish brown), apple tree (yellowish-pinkish-light brown), apricot, Walnut(light (dark) brown);
red - yew, maklura, paduk, mahogany;
red-violet - amaranth;
pink - laurel cherry (yellowish pink), pear, alder, plane tree (dark pink);
orange - buckthorn;
purple - lilac, privet (core);
black - bog oak, ebony, macassar;
greenish - persimmon, pistachio.
2. Glitter wood- this is the ability to reflect the light flux from the surface in a certain direction. Different breeds have different luster; to a large extent, this property is manifested in beech, maple, plane trees, white acacia. Poplar, linden, aspen, teak have a matte (satin) sheen; silky - willow, elm, ash, bird cherry; golden - cherry; silver - Siberian cedar; moire - birch, gray maple, laurel cherry.
The brilliance of wood depends not only on the presence and size of the core rays, but also on the nature of their placement along the cuts: the larger the core rays (for example, in oak) and the denser the wood, i.e., the more densely the core rays are located (for example, in maple ), the more significant will be the shine of the wood. The distribution of gloss over the surface is not the same and depends on the type of cut: in the radial plane it is stronger, in the transverse plane it is weaker.
Chiaroscuro overflows in some rocks are clearly visible only in the longitudinal section of the trunk, in others - in all sections. They significantly affect the decorative qualities of wood, enhancing or weakening its expressive sound, so the shine of wood is taken into account when compiling mosaic sets.
Distinctive features and application of tree species.
3. Wood texture.
The texture of wood is the natural pattern of wood fibers on the treated surface, due to the peculiarities of its structure. Texture depends on features anatomical structure individual species of wood and the direction of the cut. It is determined by the width of the annual layers, the difference in the color of early and late wood, the presence of core rays, large vessels, and the wrong arrangement of fibers (wavy or confused). Conifers on a tangential section due to a sharp difference in the color of early and late wood have a beautiful structure. Hardwoods with pronounced annual layers and developed core rays (oak, beech, maple, elm, elm, plane tree) have a very beautiful structure of radial and tangential sections. A particularly beautiful pattern on cuts of wood with a directional and tangled (loose) arrangement of fibers (burls, growths), as well as with traces of dormant buds (eyes). Softwood and soft hardwood have a simpler and less varied pattern than hard hardwood. The decorative value of wood is determined by the texture, which is enhanced and revealed with transparent varnishes.

Wood texture
Table 1.

The smell of wood.

The smell of wood depends on the amount of essential oils, resins and tannins. The wood of a freshly felled tree or immediately after its mechanical processing has a strong odor, softwoods have a stronger odor than hardwoods.
The characteristic smell of turpentine in conifers is pine, spruce. Oak has the smell of tannins, bakout and rosewood - vanilla. By the smell of wood, you can determine its breed.

macrostructure

The macrostructure is characterized by the width of the annual layers, determined by the number of layers per 1 cm of the segment, measured in the radial direction on the transverse section. Coniferous wood has higher physical and mechanical properties if there are at least 3 and no more than 25 layers in 1 cm. In deciduous ring-vascular species (oak, ash), an increase in the width of the annual layers occurs due to the late zone and, therefore, strength, density and hardness increase. The wood of deciduous scattered vascular species (birch, beech) does not have a clear dependence of properties on the width of the annual rings. According to the samples of wood of coniferous and ring-shaped deciduous species, the content of late wood is determined as a percentage. The higher the content of late wood, the greater its density and, therefore, the better the mechanical properties.

Humidity.

Humidity (absolute) wood is the ratio of the mass of moisture in a given volume of wood to the mass of absolutely dry wood, expressed as a percentage.
Moisture in wood impregnates cell membranes (bound or hygroscopic) and fills cell cavities and intercellular spaces (free or capillary).
When wood dries, first free moisture evaporates from it, and then hygroscopic. When wood is moistened, moisture from the air impregnates only the cell membranes until they are completely saturated. Further moistening of wood with filling of cell cavities and intercellular spaces occurs only with direct contact of wood with water (soaking, steaming). It follows from this that once dried wood, not being in direct contact with water, cannot have a moisture content above the hygroscopic limit. - the state of wood, in which the cell membranes contain the maximum amount of bound moisture, and only air is in the cell cavities.
The complete saturation of wood with water is called the hygroscopic limit. This stage of humidity, depending on the type of wood, is 25-35%.
Wood obtained after drying at a temperature of 105 ° C with the complete release of all hygroscopic moisture is called absolutely dry wood.
In practice, wood is distinguished: room-dry (with a moisture content of 8-12%), air-dry artificial drying (12-18%), atmospheric-dry wood (18-23%) and wet (humidity exceeds 23%).
Wood from a tree that has just been felled or has been for a long time in water is called wet, its humidity is up to 200%. There is also an operational humidity corresponding to the equilibrium moisture content of wood in specific conditions.

Average humidity in fresh cut condition, %
Table 2.

Shrinkage.

Shrinkage is the reduction in linear dimensions and volume of wood during drying. Drying begins after the complete removal of free moisture and from the beginning of the removal of bound moisture.
Shrinkage in different directions is not the same. On average, complete linear shrinkage in the tangential direction is 6...10%, in the radial direction - 3...5%, and along the fibers - 0.1...0.3%.
The decrease in the volume of wood during the evaporation of bound moisture is called volumetric shrinkage.
When sawing logs into boards, allowances for shrinkage are provided so that after drying, the lumber and blanks have the specified dimensions.

Shrinkage of wood (from water-saturated state to absolutely dry)
Table3.

Internal stresses

Stresses that arise without the participation of external forces are called internal. The reason for the formation of stresses during the drying of wood is the uneven distribution of moisture.
If the tensile stresses reach the tensile strength of the wood across the fibers, then cracks may occur: at the beginning of the drying process on the surface of the assortment, and at the end - inside.
Internal stresses are stored in the dried material and cause changes in the size and shape of parts during machining wood. Residual stresses are removed by additional processing of lumber (steam humidification).

Warping.

When the wood dries or moistens, the cross-sectional shape of the board changes. This change in shape is called warping. Warping can be transverse and longitudinal. The transverse is expressed in a change in the shape of the section of the board. This is due to the difference in shrinkage in the radial and tangential directions. Core boards decrease in size towards the edges: boards whose outer part is located closer to the tangential direction dry out more than the inner ones, which have a radial direction. The closer the board is to the core, the greater its warpage.
The boards can bend along the length, taking an arcuate shape or the shape of a helical surface (winged). The first type of longitudinal warping is found in boards containing heartwood and sapwood (shrinkage of the heartwood and sapwood varies somewhat along the length of the fibers). Winging is observed in lumber with a tangential inclination of the fibers. Proper stacking, drying and storage of wood is essential to prevent warping.

Swelling.

Swelling is an increase in the linear dimensions and volume of wood with an increase in the content of bound moisture. Swelling is observed with an increase in humidity to the limit of hygroscopicity; an increase in free moisture does not cause swelling. As well as shrinkage, the greatest swelling of wood is observed in the tangential direction across the fibers, and the smallest - along the fibers.

Water absorption.

Water absorption - the ability of wood, due to its porous structure, to absorb drop-liquid moisture. Water absorption occurs when wood comes into direct contact with water. At the same time, the content of both bound and free moisture in the wood increases.

wood density

The density of wood depends on moisture content and for comparison, the density values ​​always lead to a single moisture content of 12%.
There is a close relationship between the density and strength of wood. Heavier wood tends to be more durable.
The density value varies over a very wide range. By density at a moisture content of 12%, wood can be divided into three groups:
- rocks with a low density (510 kg / m 3 or less): pine, spruce, fir, cedar, poplar, linden, willow, alder, chestnut, walnut;
- rocks of medium density (550 ... 740 kg / m 3): larch, yew, birch, beech, elm, pear, oak, elm, elm, maple, plane tree, mountain ash, apple tree, ash; - breeds with high density(750 kg / m 3 and above): white acacia, iron birch, hornbeam, boxwood, saxaul, pistachio, dogwood.

Density of wood (g / cm 3)
Table 4