Tree species that can be used in the construction of a sauna, comparison of their physical properties in terms of suitability
Breed	Density	Heat capacity	Thermal conductivity	Water absorption			Resistance to splitting	Rot resistance	Core color	Notes
				T	R	T+R
Group A: with a resinous odor
Norway spruce (Picea abies)	472	812	0,127	0,26	0,13	Moderately large	2	3	Almost white	Traditional wood for sauna; contains relatively little resin; the smell is not very strong. Sometimes sold together with fir, which has bad smell. Contains small, dark, hard strands, usually scruffy
Lodgepole pine (Pinus contorta)	468	805	0,125	0,23	0,15	Moderately large	3	3	Light red-brown	It has smooth, straight fibers and can be very curled. Has a distinct resinous odor
Lambert's pine, or sugar pine (Pinus lambertiana)	417	717	0,113	0,19	0,09	Small	1	3	Light creamy brown	Very hard wood with a sweet smell of resin
Weymouth black pine (Pinus monticoia)	449	772	0,120	0,24	0,14	Moderately large	2	3	Cream to light	It can be very wilted; contains many dense red fronds. The smell of resin is not very strong
Yellow pine (Pinus ponderosa)	458	788	0,123	0,12	0,13	Moderately small	1	3		A very strong tree with even, straight grain. Has a distinct resinous odor. The most resinous variety that grows in Canada.
Radiata pine (Pinus radiata)	485	834	0,130	0,24	0,16	Big	2	3	Yellow-brown	Only wood from young trees is suitable for a sauna, as it is quite light; old trees can have a density of up to 600 kg/m. cube Moderately resinous and curly; not very durable. The smell of resin is not very strong
Resin pine (Pinus resinosa)	503	865	0,134	0,24	0,16	Moderately large	2	3	Orange to reddish brown	Moderately strong wood, can be heavily saturated with resin. Has a strong resinous odor
Weymouth pine (Pinus strobus)	407	700	0,110	0,20	0,08	Small	2	2	Cream to light reddish brown	A very strong wood with a uniform texture and high resistance to splitting. Has a subtle resinous odor
Scots pine (Picea abies)	521	896	0,139	0,28	0,13	Big	2	3	Pinkish light brown	Traditional wood for sauna; contains many resinous strands with very a large number resin. Has a moderately strong resinous odor
Pseudotsuga taxifolia	528	908	0,140	0,26	0,14	Big	3	2	Orange to red, sometimes yellow	Wood with even grains is very prone to splitting and splintering. It has a characteristic resinous smell, not as pleasant as pine. Wood is corroded by iron
Group B: with a pleasant smell
Mexican cedrela (Cedraia spp.)	488	839	0,130	0,21	0,14	Moderately large	1	1	Reddish light brown	Hardwood. It has a distinct slightly spicy smell. Smooth texture, resistance to splitting. Resin free
Cedrela toona	439	755	0,118	0,20	0,11	Moderately small	1	1	... Same	... Same
Lawson's cypress (Chamaeparis lawsonia)	482	829	0,128	0,23	0,16	Moderately large	1	1	Light yellow to pale brown	Exceptional aroma that lasts for years. Smooth straight fiber texture. Resin free
Franklin's dacrydium (Dacrydium franklinii)	537	924	0,114	0,27	0,14	Big	2	1	Pale yellow to tan	An oily tree with a characteristic pine odor, which can be very strong at first
River cedar, or Californian cedar (Libocedrus decurrens)	409	703	0,111	0,18	0,11	Small	2	1	Red-brown	Excellent uniform texture. Strong spicy odor
Western thuja (Pinus ponderosa)	352	605	0,096	0,16	0,07	Very small	2	1	Tan	Characteristic spicy smell, very soft wood, easy to split. Both types are sold as white cedar
Thuja giant, or folded (Thuja plicata)	375	695	0,102	0,17	0,08	Small	3	1	Reddish brown	Gets dirty with metal and tends to split easily. One of the most strong trees. Characteristic smell of cedar
Group C: mild or odorless
Great fir (Abies spp.)	440	757	0,118	Changeable		Small to moderately large	1 - 3	3	Almost white to pale reddish brown	Several species with the same characteristics are sold under this name. The unpleasant smell of green wood disappears after aging
Palmerston's Agathis (Aqathis paimerstoni)	461	793	0,124	0,17	0,14	Moderately small	2	3	Pale cream to light brown	Local in Australia. Other types of agathis are too dense. Excellent regular fiber structure. Odorless.
Araucaria angustifolia	553	951	0,149	0,31	0,21	Very large	3	3	Variegated: brown to bright red with dark stripes	Local in South America. Usually too dense for a sauna. Odorless
Araucaria cunninghamii	497	855	0,134	0,23	0,18	Big	2	3	Very pale brown to tan	Local in Australia. Only logs from young trees are light enough for a sauna. Excellent regular fiber structure. Odorless
Engelmann spruce (Picea engelmannii)	386	664	0,105	0,22	0,11	Moderately small	2	3	Almost white	Very soft wood with even grain, odorless
Canadian or white spruce (Picea giauca)	471	810	0,126	0,24	0,13	Moderately large	2	3	Almost white	Smooth texture, straight fibers, odorless
Sitka spruce (Picea sitchensis)	450	774	0,120	0,20	0,14	Moderately small	1	3	Light reddish brown	Smooth texture. Elastic wood, odorless
Poplar (Populus spp.)	450	774	0,120	Changeable		Moderately large to large	3	3	Grayish white to pale brown	Solid wood. American and European varieties have the same properties: a very good fibrous structure without strands. Very resistant to splitting
Evergreen sequoia (Seguoia sempervirens)	458	788	0,123	0,14	0,09	Very small	1	1	Cherry to deep red-brown	Wood with straight grain; prone to splintering, resistant to rot and extreme temperatures. Sweat and metal stains may form. Very durable
Linden (Tillia spp.)	417	717	0,112	0,31	0,22	Very large	3	3	Creamy white to creamy brown	Heavy wood. Excellent even texture and straight grain
Triplochiton scleroxylon	384	661	0,103	0,18	0,11	Small	2	3	Yellowish	Durable wood. Smooth, beautiful fibers, very resistant to splitting
Western hemlock (Tsuga herarophylla)	474	815	0,128	0,25	0,12	Moderately large	3	3	Light red brown	Smooth fibers. Non-resinous. Faint sour odor when the wood is fresh

1. Density is given at 15% moisture content and represents average value for each breed. The density of these wood species varies widely depending on the geographic area where it grew and also depending on where the sample was cut from the log. The values ​​given in columns 2 and 3, calculated from density, also have an average value for each breed.

2. These values ​​indicate the amount of heat in kJ required to raise the temperature of 1 m of wood by 1°. The heat capacity of soft wood with 2% moisture content and at 90°C is approximately 1.72 kJ/kg°C. The lower the number in this column, the better.

3. Thermal conductivity (K) of wood is given at 2% moisture content and at 90°C, which corresponds to normal conditions in the sauna while using it. The lower the digital value, the better.

4. Water absorption of wood, tangential and rational, is given as a percentage of its value at 20% moisture content for every 1% decrease in moisture content. The percentage of water absorption is determined by adding the water absorption in the tangential and radial directions (T+R) as follows: 0.25 - very small; 0.25-0.28 - small; 0.30-0.34 - moderately small; 0.35-0.39 - moderately large; 0.40 is big. A small change in humidity is preferable.

5. To compare the resistance of wood to splitting due to drying (compression), the corresponding properties of tensile forces acting perpendicular to the grain were expressed as a function of their percentage designation of tangential moisture movement. The obtained figures were classified into the following three categories: 1 - high resistance to splitting, 2 - medium, 3 - low. How less value in this column, so much the better.

6. Rot resistance has been classified into three categories as follows: 1 - rot resistant, 2 - moderately resistant, 3 - non-rot resistant.

The varieties listed below, although similar in some properties to the varieties listed in Table 1, are not suitable for building a sauna
Abies alba	European white fir, or comb fir	Unpleasant sour smell
Cedrus spp.	Thuja gigantea	Lots of knots, very dense, with a strong smell
Chamaeparis nootkaneusis	Nootka cypress	Unpleasant smell
Luniperus virginiana	Juniperus virginiana, or pencil tree	Lots of knots, high density
Larix deciolua	European larch	High density, easy to split
Larix occidentalis	Western larch	Too tight
Pinus banksiana	Banks Pine	Too resinous, too many knots
Pinus palustris	Swamp pine
Pinus pinaster	Maritime pine	High density
Pinus rigidola	Pine hard	Too dense, very resinous
Pinus serotina	Late pine	High density
Pinus spp.	Caribbean pine	Too dense, very resinous
Pinus virginiana	Virginia pine	High density
Taxodium distichum	Swamp cypress ascending	Unpleasant musty smell

Each type of wood, in addition to its special properties, also has a unique individual smell. It can be very persistent and strong, or, on the contrary, subtle - but it is certainly present in any case. Experts are able to determine the identity of a wood material, focusing only on how it smells.

Perhaps some people are familiar with the smell of wood that reigns in a carpentry workshop - it is quite characteristic, reminiscent of turpentine. At the same time, however, if, for example, pine is being sawed at this moment, the pine aroma drowns out everything else. There are some other tree species with the same feature.

By the way, the ability to retain odor must be taken into account if you order furniture or other items made of natural wood. Sometimes it lasts for quite a long time. What determines whether the wood will smell intensely after cutting or not? As a rule, it’s all about the amount of resin and other substances (including tannins).

The heartwood of wood smells the strongest because it is there that the amount of odorous substances reaches its maximum concentration. A tree that has just been cut down has the strongest smell, but then the smell becomes weaker and may even change. Rosewood and buckout have, say, a vanilla scent. In practice, pleasant woody odors are taken into account when making containers for products, such as honey and butter.

Juniper and cypress, lemon tree, orange tree, and tulip tree smell pleasant. Thuja smells of bergamot, rosewood smells of roses, acacia smells of violets or raspberries, star anise smells of anise, peach smells of almonds, yellow tree- lemon or musk. Pleasant and also useful. Because they work as a natural antiseptic, purifying the air from harmful impurities and microorganisms. It is easy to breathe in rooms made of natural wood, which is beneficial for people and pets.

Teak smells like rubber, balsam poplar smells like tanned leather, and camphor laurel smells like camphor. Sterculia and paulownia have very unpleasant odors, as well as ginkgo, winged lophyra and some others. All these trees grow in other countries and even on other continents.

By the way, this is why you shouldn’t get too carried away with the exotic when decorating and purchasing interior items. At first, it would be useful to ask what kind of wood it is and where it comes from, to find out everything about it if it belongs to unfamiliar species.

Camphor wood, teak, and juniper retain the scent after drying. Disappears in acacia, walnut, oak, and alder.

If the smell of the wood has changed, this most likely indicates that the process of rotting has begun. Another case is juniper, which has long dried up in the forest and has been endlessly exposed to various precipitation, frost, etc. And, nevertheless, if you break off a branch from it, a strong aroma will be felt immediately. Moreover, if you wet the cut area, it will become even more intense. True, it also happens that mushrooms that have a destructive effect on wood give it a pleasant aroma. Let's say the pine needles have a vanilla smell.

Oak, cedar, and cherry also have wood that has a fairly persistent, unique odor. True, it is not so easy to describe it in words. The classification of odors according to their strength has not yet been sufficiently developed, but there is some data on this topic. They go in descending order:

• Pine (very strong odor, 2000 mg/l air)
• Juniper
• Pine resin
• Birch

By the way, in terms of intensity, substances such as ethyl alcohol, vinegar, chloroform, and musk follow the trees. Compared to the above plants, their odor strength is rather weak.

The smell of wood depends on the resins it contains, essential oils, tannins and other substances. Conifers - pine and spruce - have a characteristic smell of turpentine. Oak smells of tannins, while backout and rosewood smell of vanilla. Juniper smells pleasant, so its branches are used to steam barrels. The smell of wood is of great importance when making containers. When freshly cut, wood has a stronger odor than after drying. The kernel smells stronger than the sapwood. Individual species can be identified by the smell of wood.

2.5. Macrostructure

Macrostructure. To characterize wood, it is sometimes sufficient to determine the following macrostructure indicators.

The width of the annual layers is determined by the number of layers per 1 cm of a segment measured in the radial direction on the end section. The width of the annual layers affects the properties of wood. For coniferous wood, an improvement in properties is noted if there are at least 3 and no more than 25 layers in 1 cm. In deciduous ring-vascular species (oak, ash), the increase in the width of the annual layers occurs due to the late zone and therefore the strength, density and hardness increase. For wood of deciduous scattered vascular species (birch, beech) there is no such clear dependence of properties on the width of the annual layers.

The content of late wood (in%) is determined on samples from coniferous and ring-vascular deciduous wood. The higher the latewood content, the greater its density, and therefore the higher its mechanical properties.

The degree of equilayering is determined by the difference in the number of annual layers in two adjacent sections 1 cm long. This indicator is used to characterize the resonant ability of spruce and fir wood.

When processing wood with cutting tools, hollow anatomical elements (vessels) are cut and irregularities are formed on the surface of the wood. In species such as oak, ash, and walnut, the amount of structural irregularities is significant. Since the wood of these species is used for finishing products, before polishing it is necessary to reduce the size of these irregularities. For this purpose, a special operation is performed, which is called pore filling.

2.6. Wood moisture content

The moisture content of wood is understood as the ratio of the amount of moisture removed to the mass of wood in an absolutely dry state. Wood moisture content is expressed in %.

Absolutely dry wood in small samples can be obtained by drying it in special cabinets. In nature and in production, wood always contains some amount of moisture. Moisture in wood permeates cell membranes and fills cell cavities and intercellular spaces. Moisture that permeates cell membranes is called bound or hygroscopic. Moisture that fills cell cavities and intercellular spaces is called free, or capillary. When wood dries, first free moisture evaporates from it, and then hygroscopic moisture. When moistening wood, moisture from the air permeates 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, rafting, rain).

The total amount of moisture in wood consists of free and bound moisture. The maximum amount of free moisture depends on how large the volume of voids in the wood is that can be filled with water. The condition of wood in which the cell membranes contain the maximum amount of bound moisture, and the cell cavities contain only air, is called the hygroscopic limit. Thus, the humidity corresponding to the hygroscopic limit at room temperature (20°C) is 30% and practically does not depend on the breed. When hygroscopic humidity changes, the dimensions and properties of wood change dramatically. The following stages of wood moisture are distinguished: wet - exposed to water for a long time, humidity above 100%; freshly cut - humidity 50-100%; air-dry - for a long time stored in air, humidity 15-20% (depending on climatic conditions and time of year); room-dry - humidity 8-12% and absolutely dry - humidity 0%. The moisture content in the trunk of a growing tree varies along the height and radius of the trunk, and also depending on the time of year. The moisture content of pine sapwood is three times higher than the moisture content of the core. In deciduous trees, the change in humidity along the diameter is more uniform. Along the height of the trunk, the moisture content of the sapwood in conifers increases up the trunk, but the moisture content of the core does not change. In deciduous trees, the moisture content of the sapwood does not change, but the moisture content of the core decreases up the trunk. Young trees have higher humidity and its fluctuations throughout the year are greater than older trees. The greatest amount of moisture is contained in the winter (November-February), the minimum - in the summer months (July-August). The moisture content in the trunks changes throughout the day: in the morning and evening the humidity of the trees is higher than during the day.

To determine the moisture content of wood, gravimetric and electrical methods are used. With the weight method, samples of prismatic wood measuring 20x20x30 mm are cut, cleaned of sawdust and burrs, after which they are immediately weighed with an error of no more than 0.01 g. Then they are placed in a drying cabinet and kept at a temperature of 103 + 2 ° C. The temperature should not be raised above 105°C to avoid the release of resin (from conifers) and decomposition of the wood. The first weighing of the sample is carried out depending on the type of wood 6 hours after the start of drying (samples of oak and ash wood after 10 hours), the second and subsequent ones - every 2 hours. Dry the sample to a constant weight, i.e. until upon further weighing, its mass will cease to change.

Wood moisture content W, determined by weight, is calculated as a percentage using the formula

W=[(m1-m2)/m2]x100,

where m1 is the mass of the wood sample before drying, g; m2 is the mass of the same sample in an absolutely dry state, g. The advantage of the weight method is a fairly accurate determination of wood moisture content for any amount of moisture. Its disadvantage is the duration of sample drying (from 12 to 24 hours).

With the electrical method, wood moisture content is determined using an electric moisture meter. The operation of this device is based on measuring the electrical conductivity of wood depending on changes in its humidity. The working part of the most common electric moisture meter is needles with electrical wires connected to them. The needles of an electric moisture meter (sensor) are inserted into the wood to a depth of 8 mm and an electric current is passed through them, while the actual moisture content of the wood is immediately shown on the dial of the device. The advantage of the electrical method is the speed of determination and the ability to check the moisture content of wood of any size. Disadvantages - determination of humidity only at the point of contact of wood with the sensor; low accuracy. In the measurement range up to 30% humidity, the error is 1-1.5%, above 30 ±10%.

This is a set of characteristics that are easy to identify without disturbing the integrity of the lumber and which allow one to be distinguished from another. 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 - all wood really has a smell. Odorless wood also has its own smell, it is simply not detected by the human sense of smell.

The smell of wood associated with the presence of tannins, resins and essential oils in the material. The intensity and durability of the aroma depends on their quantity.

Almost all freshly cut 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. Not all types of wood can boast of having a persistent odor for a long time, even after drying.

The smell of wood is an important physical property.

What does the smell of wood tell us:

About the belonging of lumber to a certain species. Experienced craftsmen can accurately name the type of wood just by smell;

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

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

The heart of the wood has the most intense odor; it contains the maximum concentration of tannins and essential substances.

The smell of wood has not only distinctive, but also beneficial properties. Along with the scents in environment substances with antiseptic and bactericidal properties are released, helping to purify the air in the room. That’s why it’s so easy and free to breathe in a house made of wood.

What is the smell of different types of wood?

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 wood odors can be divided into pleasant and unpleasant. The wood of juniper, cypress, citrus trees, rosewood, acacia and peach has such a pleasant, attractive smell for humans. But teak, laurel and poplar wood has a pungent and unpleasant odor. Coniferous wood has the most persistent odor due to a large number 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 lasts for a fairly long period.

As for hardwoods, they smell weaker; the intensity and persistence of the smell is affected by the amount of tannins in the wood. For example, linden wood smell very durable and preserves even after drying and processing. The substance is responsible for the smell of linden. - phraseol, of which there is a lot in the structure of the tree. This smell is familiar to everyone - sweet with honey notes. It is from linden wood that barrels for storing honey are made.

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

The smell of birch wood practically undetectable to humans. Therefore, such wood is often used to make dishes or containers for storing cereals.

Irina Zheleznyak, Staff correspondent for the online publication "AtmWood. Wood-Industrial Bulletin"

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PHYSICAL PROPERTIES OF WOOD

These include: appearance, smell, macrostructure indicators, humidity and associated 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.Wood color.
Under color wood understand a certain visual sensation, which depends mainly on spectral composition the light flux reflected by it. Color is one of the most important characteristics appearance wood It is taken into account when choosing species for interior decoration, furniture manufacturing, musical instruments, artistic crafts, etc.
The wood of oak, beech, white acacia, and velvet tree has the greatest shine among domestic species; from foreign ones - satinwood and mahogany (mahogany) wood.
Wood color shades have a wide range. It must be remembered that the color of wood can vary not only depending on the species, but within one species there can be several dozen variants of tonal relationships. This factor is influenced climatic conditions, in which the tree and other natural factors grew. Identifying and using a color palette is a crucial moment in the design search. The color of wood is given by coloring tannins found in its fiber. Wood species with warm shades predominate (yellow, ocher, red, red-brown, brown), but there are green, blue, purple and black wood species, which are considered exotic in our country.
Color shades various breeds can be classified into main groups, where one color of wood will be predominant:
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, rowan (brown-brown), acacia (yellow-brown), Anatolian walnut ( greenish-brown);
brown - cherry (yellowish-brown), apple (yellowish-pinkish-light brown), apricot, walnut(light (dark) brown);
red - yew, maclura, paduk, mahogany;
red-violet - amaranth;
pink - cherry laurel (yellowish-pink), pear, alder, plane tree (dark pink);
orange - buckthorn;
purple - lilac, privet (kernel);
black - stained oak, ebony, Macasar;
greenish - persimmon, pistachio.
2. Wood shine- this is the ability to reflect light flux from a surface in a certain direction. Different breeds have different shine; To a large extent, this property is manifested in beech, maple, plane tree, and white acacia. Poplar, linden, aspen, and teak have a matte (satin) sheen; silky - willow, elm, ash, bird cherry; golden - cherry; silver - Siberian cedar; moire - birch, gray maple, cherry laurel.
The shine of the 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 crowded the core rays are located (for example, in maple ), the greater the shine of the wood. The distribution of gloss over the surface is uneven and depends on the type of cut: in the radial plane it is stronger, in the transverse plane it is weaker.
The light and shadow tints in some species are clearly visible only in a 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 use of wood species.
3. Wood texture.
Wood texture 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 breeds wood and cutting direction. It is determined by the width of the annual layers, the difference in the color of early and late wood, the presence of medullary rays, large vessels, and irregular arrangement of fibers (wavy or tangled). Coniferous species in a tangential section have a beautiful structure due to the sharp difference in the color of early and late wood. Deciduous species with pronounced annual layers and developed medullary rays (oak, beech, maple, elm, elm, plane tree) have a very beautiful structure of radial and tangential sections. There is a particularly beautiful pattern on sections of wood with a directional and confused (twisted) arrangement of fibers (burls, growths), as well as with traces of dormant buds (eyes). Softwoods and softwoods have simpler and less varied patterns than hardwoods. The decorative value of wood is determined by its texture, which is enhanced and revealed with transparent varnishes.

Wood texture
Table 1.

Wood name	Texture
White acacia	Stripes, rings, thin lines
	Dark brown stripes, dashes
Common birch	Moire pattern, silky shine
Karelian birch	Pattern in the form of brown convolutions or dashes, bright
	Shiny specks, dark thin strokes
	Sound breed, striped
	The texture is weak
	Large texture with annual layers, large vessels, core rays in the form of flames, dark strokes
	Moire texture with silky shine
Russian maple	Delicate pink texture, silky shine
Maple: sycamore and bird's eye	Silky shine
lemon tree	Ribbon texture
Mahogany	Band structure
	Texture is expressed
Walnut	Beautiful texture with dark veins
	The texture is weak
Rosewood	The texture is large, expressive with dark short lines
	With small pores, weakly expressed
	Texture with barely noticeable veins, weakly expressed
	The texture is large and expressive. Reminds the texture of a nut
	The texture is weakly expressed, homogeneous
	The texture is sharply expressed in the form of stripes

The smell of wood.

The smell of wood depends on the amount of essential oils, resins and tannins. Wood from a tree that has just been felled or has been mechanically processed has a strong odor; conifers have a stronger odor than hardwoods.
The characteristic smell of turpentine is found in conifers - pine and spruce. Oak smells of tannins, while backout and rosewood smell of vanilla. You can determine the type of wood by the smell of wood.

Macrostructure

The macrostructure is characterized by the width of the annual layers, determined by the number of layers per 1 cm of a segment measured in the radial direction on a 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), the increase in the width of the annual layers occurs due to the late zone and therefore the strength, density and hardness increase. The wood of deciduous scattered vascular species (birch, beech) does not have a clear dependence of its properties on the width of the annual layers. Based on samples of coniferous wood and ring-vascular deciduous species, the latewood content is determined as a percentage. The higher the latewood content, the greater its density and, therefore, the better the mechanical properties.

Humidity.

The moisture content of (absolute) wood is the ratio of the mass of moisture contained in a given volume of wood to the mass of absolutely dry wood, expressed as a percentage.
Moisture in wood permeates 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 moisture. When moistening wood, moisture from the air permeates 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, without being in direct contact with water, cannot have a moisture content above the hygroscopic limit - state of wood in which the cell membranes contain maximum quantity bound moisture, and in the cavities of the cells there is only air.
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 o C with the complete release of all hygroscopic moisture is called absolutely dry wood.
In practice, wood is distinguished: room-dry (with a humidity of 8-12%), air-dry artificially dried (12-18%), atmospheric-dry wood (18-23%) and damp (humidity exceeds 23%).
Wood from a tree that has just been cut down or has been in water for a long time is called wet, its moisture content is up to 200%. There is also operational humidity, which corresponds to the equilibrium moisture content of wood under specific conditions.

Average humidity in freshly cut condition, %
Table2.

Breed
Larch
Scots pine
Siberian cedar pine
Small-leaved linden
Common ash

Shrinkage.

Shrinkage is a reduction in the linear dimensions and volume of wood during drying. Drying begins after the complete removal of free moisture and the beginning of the removal of bound moisture.
Shrinkage by different directions 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 reduction in wood volume due to the evaporation of bound moisture is called volumetric shrinkage.
When sawing logs into boards, allowances are made for shrinkage so that after drying the lumber and workpieces have the specified dimensions.

Drying of wood (from water-saturated state to completely dry)
Table3.

Type of wood
	Longitudinal	In tangential direction	Radial direction
Balsa wood
Beech white
Beech
Larch
Pine (regular)
Resinous pine

Internal stresses

Stresses that arise without the participation of external forces are called internal. The reason for the formation of stress when drying wood is the uneven distribution of moisture.
If tensile stresses reach the limit of the wood's tensile strength across the grain, cracks may appear: at the beginning of the drying process on the surface of the log, and at the end - inside.
Internal stresses remain in the dried material and cause changes in the size and shape of parts during mechanical processing of wood. Residual stresses are removed by additional processing of lumber (steam humidification).

Warping.

When wood dries or gets wet, the cross-sectional shape of the board changes. This change in shape is called warping. Warping can be transverse and longitudinal. Transverse is expressed in a change in the cross-sectional shape of the board. This happens 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 shrink more than the inner ones, which have a radial direction. The closer the board is to the core, the greater its warping.
The boards can bend along their length, taking on an arched shape or the shape of a helical surface (winged). The first type of longitudinal warping occurs in boards containing core and sapwood (the shrinkage of core and sapwood along the length of the fibers is slightly different). Winging is observed in lumber with tangentially inclined fibers. To prevent warping, proper laying, drying and storage of wood is necessary.

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 increasing humidity to the hygroscopic limit; an increase in free moisture does not cause swelling. Just like shrinkage, the greatest swelling of wood is observed in the tangential direction across the grain, and the least - along the grain.

Water absorption.

Water absorption is the ability of wood, due to its porous structure, to absorb droplet-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 humidity and for comparison, density values ​​always lead to the same humidity - 12%.
There is a close relationship between the density and strength of wood. Heavier wood is generally more durable.
The density value varies within very wide limits. Based on density at a humidity of 12%, wood can be divided into three groups:
- low-density species (510 kg/m3 or less): pine, spruce, fir, cedar, poplar, linden, willow, alder, chestnut, walnut;
- medium density species (550...740 kg/m3): larch, yew, birch, beech, elm, pear, oak, elm, elm, maple, plane tree, rowan, apple, ash; - species with high density (750 kg/m3 and above): white acacia, iron birch, hornbeam, boxwood, saxaul, pistachio, dogwood.

Wood density (g/cm3)
Table 4.

Siberian fir
Sequoia evergreen
Mahogany
horse chestnut
Edible chestnut