Contenido

En composición media se constituye de un 50 % de carbono (C), un 42 % de oxígeno (O), un 6 % de hidrógeno (H) y el 2 % restante de nitrógeno (N) y otros elementos.[6]​.

Los componentes principales de la madera son la celulosa, un polisacárido que constituye alrededor de la mitad del material total, la lignina (aproximadamente un 25 %), que es un polímero resultante de la unión de varios ácidos y alcoholes fenilpropílicos y que proporciona dureza y protección, y la hemicelulosa (alrededor de un 25 %) cuya función es actuar como unión de las fibras. Existen otros componentes minoritarios como resinas, ceras, grasas y otras sustancias.

Cellulose

Cellulose is a structural polysaccharide formed by glucose that is part of the wall of plant cells. Its empirical formula is (CHO), with the minimum value of n = 200.

Its functions are to serve as a skeleton for the plant and to provide plant protection. It is very resistant to chemical agents, insoluble in almost all solvents and also unalterable in dry air, its chipping temperature under pressure of one bar "Bar (pressure unit)") is approximately 232.2 °C.

Cellulose is a structural polysaccharide in plants since it is part of the supporting tissues. The wall of a young plant cell contains approximately 40% cellulose; wood 50%, while the purest example of cellulose is cotton with a percentage greater than 90%.

Although it is made up of glucose, most animals cannot use cellulose as a source of energy, since they do not have the enzyme necessary to break the β-1,4-glycosidic bonds; However, it is important to include it in the human diet (dietary fiber) because when mixed with feces, it facilitates digestion and defecation, as well as prevents bad gas.

In the intestines of ruminants, other herbivores and termites there are microorganisms, many methanogens, that have an enzyme called cellulase that breaks the β-1,4-glucosidic bond and when the cellulose molecule is hydrolyzed, glucose becomes available as a source of energy.

There are microorganisms (bacteria and fungi) that live freely and are also capable of hydrolyzing cellulose. They have great ecological importance, as they recycle cellulosic materials such as paper, cardboard and wood. Among them, the fungus Trichoderma reesei") stands out, capable of producing four types of cellulases: the 1,4-β-D-glucancelobiohirolases CBH i and CBH II and the endo-1,4-β-D-glucanase EG I and EG II. Using biotechnological techniques, these enzymes are produced that can be used in paper recycling, reducing the economic cost and pollution.

The wood arrives and is stripped of bark and chipped, and thrown into the storage boiler and from there to a washing classification where it is selected and bleached, later dried and packaged. The leftovers go to silos that will later be used to provide energy.

Depending on the purpose of the paper, different methods are used to obtain the pulp for its manufacture:

• - Kraft process or Kraft pulping, it is treated with sodium sulfide solution and sodium hydroxide in a 1:3 ratio for 2-6 h at temperatures of 160-170 °C. Then, while boiling, sodium sulfate is added, which subsequently turns into sodium sulfide and is eliminated.

• - Soda method: sodium hydroxide is used to digest the material.

• - Sulfite method: it is digested with calcium bisulfite solution with free sulfur dioxide, and the lignins are transformed into soluble lignosulfonates.

Lignin

Lignin is a polymer present in the cell walls of organisms of the kingdom Plantae and also in the Dinophytas of the kingdom Chromalveolata. The word lignin comes from the Latin term lignum, which means 'wood'; Thus, plants that contain a large amount of lignin are called woody. Lignin is responsible for thickening the stem.

Lignin is used by the plastics industry.[7]​.

Las propiedades físicas de la madera varían según la especie del árbol origen e incluso dentro de la misma especie por las condiciones del lugar de crecimiento. Aun así hay algunas características cualitativas comunes a casi todas las maderas.

La madera es un material anisótropo en muchas de sus características, por ejemplo en su resistencia o elasticidad.[8]​.

Si al eje coincidente con la longitud del tronco le nombramos como axial y al eje que pasa por el centro del tronco (médula vegetal) y sale perpendicular a la corteza le llamamos transversal, podemos decir que la resistencia de la madera en el eje axial es de 20 a 200 veces mayor que en el eje transversal.[8]​.

La madera es un material ortótropo ya que su elasticidad "Elasticidad (mecánica de sólidos)") depende de la dirección de deformación.

Tiene un comportamiento higroscópico, pudiendo absorber humedad tanto del ambiente como en caso de inmersión en agua, si bien de forma y en cantidades distintas.[9]​.

La polaridad "Polaridad (química)") de la madera le hace a fin con otros productos polares como agua, barnices, pegamentos con base de agua, etc.[10]​.

La densidad de la madera varía notablemente entre especies. Una vez secas, hay especies que apenas alcanzan los 300 kg/m³ (Cecropia adenopus) mientras que otras pueden llegar a superar los 1200 kg/m³ (Schinopsis balansae).[11]​ No obstante la densidad habitual de la mayoría de especies se encuentra entre los 500 y los 800 kg/m³ (peso seco). La densidad también puede variar significativamente en una misma especie, o incluso en un mismo árbol, en función de la altura del fuste y de la distancia al centro del tronco.

Wood hardness

According to its hardness, wood is classified as:.

• - Hard woods: are those that come from slow-growing trees, so they are denser and withstand inclement weather better than soft woods. These woods generally come from deciduous trees, but they can also be evergreen, which take decades, and even centuries, to reach the sufficient degree of maturity to be cut and used in the production of furniture or beams for farmhouses or single-family homes. They are much more expensive than soft ones, because their slow growth causes them to be scarce, but they are much more attractive to build furniture with. They are also widely used to make wood carvings or any product in which quality solid wood is necessary. Trees that are classified within this type: beech, oak, walnut, maple "Acer (plant)"), hornbeam, teak, lapacho, etc.

• - Softwoods"): includes the wood of trees belonging to the order of conifers and other fast-growing ones. The great advantage they have with respect to hardwoods is their lightness and much lower price. They do not have as long a life as the hardwoods. The handling of softwoods is much simpler, although it has the disadvantage of producing a greater quantity of splinters. The lack of grain of this wood makes it less attractive, which is why it is almost always It is necessary to paint, varnish or stain it. Some widely used softwoods are: pine, fir, birch, poplar, cypress, balsa, etc.

Chestnut has a medium hardness and is very flexible, so it can be included in both groups.

The first wood product produced by man dates back to 5,255 BC. C.[12]​ Since then it has received various uses:.

• - Falling, cutting or felling: loggers with axes or electric or gasoline saws cut the tree, removing the branches, roots and bark so that it begins to dry. It is usually recommended that trees be cut in winter or fall. It is mandatory to replant more trees than those that were cut.

• - Transport: it is the second phase and it is in which the wood is transported from its cutting place to the sawmill and in this phase many things influence such as the orography and the existing infrastructure. Normally it is done by pulling with animals or machinery, but there are cases in which there is a river nearby and it is used to carry them. If there is a good current of water, the logs are released, being careful not to get stuck, but if there is little current, they are tied together, making rafts that are guided to where necessary.

• - Sawning: in this phase the wood is taken to sawmills. The sawmill divides the log into pieces, depending on the use that will be given to it later. They usually use different types of saws such as reciprocating, band, circular or roller saws. Some sawmills combine several of these techniques to improve production.

• - Drying: this is the most important process for the wood to be in good condition.

Chipboard or chipboard

It is obtained from small shavings or sawdust,[14]​ glued under pressure in a proportion of 85% shavings and 15% glue mainly. They are manufactured in different types depending on the size of their particles, their distribution throughout the board, as well as the adhesive used for their manufacture. In general, soft woods are used rather than hard ones due to the ease of working with them, since it is easier to press soft wood than hard wood.

Chipboards are stable materials with a uniform consistency, they have completely smooth surfaces and are suitable as bases for veneers. There is a wide range of these boards ranging from wood-based, paper or plastic laminates. Most chipboards are relatively brittle and have lower tensile strength than plywood because the others have perpendicularly overlapping layers of veneer that offer more strength.

This material is recommended for building all types of furniture (functional or artistic).

These boards are affected by excess humidity, presenting expansion in their thickness, an expansion that is not recovered with drying. It is not suitable for outdoors or for places in humid conditions, this type of wood swells immediately in minimal contact with water. In continuous humid conditions the boards swell to such an extent that they fall apart. However, models are manufactured with some resistance to humid conditions.

Although you should avoid placing screws along the edges of this type of sheet, if necessary, the diameter of the screws should not be greater than a quarter of the thickness of the board, to avoid cracking in the veneer on the faces.

In addition there are different types of chipboard:.

• - Oriented fiber chipboard, also known as OSB (oriented strand board*). Three-layer material made from large shavings, placed in transverse directions, simulating the structural effect of plywood. It is known by one of its trade names Aspenite.

• - Decorative chipboard that is manufactured with selected wood faces, plastic laminates or melamine. To finish the edges of these sheets, edge covers are sold that come with the same finish as the faces.

• - The three-layer agglomerate that has a core plate made up of large particles that are arranged between two layers of finer, high-density particles. Its surface is smoother and recommended for receiving paints.

• - The agglomerate of a layer that is made from particles of similar size distributed uniformly. Its surface is relatively coarse. It is recommended for veneer but not for painting directly on it.

Veneer boards

A solid wood board or sheet is relatively unstable and will experience contraction and expansion movements, mostly in the direction of the wood fibers, for this reason it is likely to suffer distortions. To counteract this effect, plywood is constructed by gluing the layers with the fibers transversely over each other, alternately. Most plywood is made up of an odd number of layers to form a balanced construction. The outer layers of a board are called faces and their quality is rated by a letter code that uses A as the best quality, B as intermediate and C as the lowest quality. The best quality side of a board is known as the "front side" and the lowest quality side is known as the "back side" or back. On the other hand, the central layer is called "soul." This is done to increase the strength of the board or piece being made.

Precomposed veneer is called a thin sheet of wood that is obtained by laminating a block of veneers starting from the edge of the block, that is, through the layers of wood pressed together. The strips of the original veneers are converted into the grain of the precomposed veneer, obtaining a grain that is perfectly straight or homogeneous.

By manipulating the contour of the sheets to be pressed, very varied configurations and very attractive appearances can be obtained. Some or all of the constituent sheets can be dyed before joining them, so that very striking appearances or colors are obtained.

Fiber boards

Fiberboards are constructed from wood that has been reduced to its basic fibrous elements and subsequently reconstituted to form a stable and homogeneous material. They are manufactured of different density depending on the pressure applied and the binder used in their manufacture.[15]​.

They can be divided into two main types, those of high density, which use the binders present in the wood itself, which in turn are divided into hard and semi-hard, and those of medium density, which use chemical agents foreign to the wood as a binder for the fibers.

They are divided into several types:[15]​.

• - Hard fiber boards.

• - Semi-hard boards, among which are low-density boards (DB) that range between 6 mm and 12 mm and are used as coverings and for control panels, and high-density boards (DA), which are used for interior coverings.

• - Medium density fiber boards characterized by having both sides smooth and manufactured using a dry process. The fibers are glued together using a synthetic resin adhesive. These boards can be worked as if they were solid wood. They make an excellent base for veneers and take "Paint (material)" paints well. They are manufactured in thicknesses between 3 mm and 32 mm.

• - Fiber boards.

• - Pavements: Wood has been used as a material in wooden pavements since ancient times, due to its ductility and insulation, but it was not until the century that it spread throughout Europe. Examples include parquet, Cosmatesque flooring and marquetry.

• - Kitchenware: crockery, cutlery.

• - Carpentry.

• - Medicine.

Wood deterioration is a process that alters its characteristics. In broad terms, it can be attributed to two primary causes:

• - biotic (living) agents.

• - abiotic (non-living) agents (can be physical, chemical, atmospheric).

In most cases, wood deterioration is a continuum, where the degrading actions are one or more agents that alter the characteristics of the wood to the degree required for other agents to attack. The inspector's familiarity with spoilage agents is one of the most important aids to effective inspection. With this knowledge, the inspection can be approached with a careful view of the processes involved in the damage and the factors that favor or inhibit its development.

• - Annex:Woods").

Literature

• - The online version is a partial view of the book.

• - Wikimedia Commons hosts a multimedia gallery on Wood.

• - Wiktionary has definitions and other information about wood.

Contenido

En composición media se constituye de un 50 % de carbono (C), un 42 % de oxígeno (O), un 6 % de hidrógeno (H) y el 2 % restante de nitrógeno (N) y otros elementos.[6]​.

Los componentes principales de la madera son la celulosa, un polisacárido que constituye alrededor de la mitad del material total, la lignina (aproximadamente un 25 %), que es un polímero resultante de la unión de varios ácidos y alcoholes fenilpropílicos y que proporciona dureza y protección, y la hemicelulosa (alrededor de un 25 %) cuya función es actuar como unión de las fibras. Existen otros componentes minoritarios como resinas, ceras, grasas y otras sustancias.

Cellulose

Cellulose is a structural polysaccharide formed by glucose that is part of the wall of plant cells. Its empirical formula is (CHO), with the minimum value of n = 200.

Its functions are to serve as a skeleton for the plant and to provide plant protection. It is very resistant to chemical agents, insoluble in almost all solvents and also unalterable in dry air, its chipping temperature under pressure of one bar "Bar (pressure unit)") is approximately 232.2 °C.

Cellulose is a structural polysaccharide in plants since it is part of the supporting tissues. The wall of a young plant cell contains approximately 40% cellulose; wood 50%, while the purest example of cellulose is cotton with a percentage greater than 90%.

Although it is made up of glucose, most animals cannot use cellulose as a source of energy, since they do not have the enzyme necessary to break the β-1,4-glycosidic bonds; However, it is important to include it in the human diet (dietary fiber) because when mixed with feces, it facilitates digestion and defecation, as well as prevents bad gas.

In the intestines of ruminants, other herbivores and termites there are microorganisms, many methanogens, that have an enzyme called cellulase that breaks the β-1,4-glucosidic bond and when the cellulose molecule is hydrolyzed, glucose becomes available as a source of energy.

There are microorganisms (bacteria and fungi) that live freely and are also capable of hydrolyzing cellulose. They have great ecological importance, as they recycle cellulosic materials such as paper, cardboard and wood. Among them, the fungus Trichoderma reesei") stands out, capable of producing four types of cellulases: the 1,4-β-D-glucancelobiohirolases CBH i and CBH II and the endo-1,4-β-D-glucanase EG I and EG II. Using biotechnological techniques, these enzymes are produced that can be used in paper recycling, reducing the economic cost and pollution.

The wood arrives and is stripped of bark and chipped, and thrown into the storage boiler and from there to a washing classification where it is selected and bleached, later dried and packaged. The leftovers go to silos that will later be used to provide energy.

Depending on the purpose of the paper, different methods are used to obtain the pulp for its manufacture:

• - Kraft process or Kraft pulping, it is treated with sodium sulfide solution and sodium hydroxide in a 1:3 ratio for 2-6 h at temperatures of 160-170 °C. Then, while boiling, sodium sulfate is added, which subsequently turns into sodium sulfide and is eliminated.

• - Soda method: sodium hydroxide is used to digest the material.

• - Sulfite method: it is digested with calcium bisulfite solution with free sulfur dioxide, and the lignins are transformed into soluble lignosulfonates.

Lignin

Lignin is a polymer present in the cell walls of organisms of the kingdom Plantae and also in the Dinophytas of the kingdom Chromalveolata. The word lignin comes from the Latin term lignum, which means 'wood'; Thus, plants that contain a large amount of lignin are called woody. Lignin is responsible for thickening the stem.

Lignin is used by the plastics industry.[7]​.

Las propiedades físicas de la madera varían según la especie del árbol origen e incluso dentro de la misma especie por las condiciones del lugar de crecimiento. Aun así hay algunas características cualitativas comunes a casi todas las maderas.

La madera es un material anisótropo en muchas de sus características, por ejemplo en su resistencia o elasticidad.[8]​.

Si al eje coincidente con la longitud del tronco le nombramos como axial y al eje que pasa por el centro del tronco (médula vegetal) y sale perpendicular a la corteza le llamamos transversal, podemos decir que la resistencia de la madera en el eje axial es de 20 a 200 veces mayor que en el eje transversal.[8]​.

La madera es un material ortótropo ya que su elasticidad "Elasticidad (mecánica de sólidos)") depende de la dirección de deformación.

Tiene un comportamiento higroscópico, pudiendo absorber humedad tanto del ambiente como en caso de inmersión en agua, si bien de forma y en cantidades distintas.[9]​.

La polaridad "Polaridad (química)") de la madera le hace a fin con otros productos polares como agua, barnices, pegamentos con base de agua, etc.[10]​.

La densidad de la madera varía notablemente entre especies. Una vez secas, hay especies que apenas alcanzan los 300 kg/m³ (Cecropia adenopus) mientras que otras pueden llegar a superar los 1200 kg/m³ (Schinopsis balansae).[11]​ No obstante la densidad habitual de la mayoría de especies se encuentra entre los 500 y los 800 kg/m³ (peso seco). La densidad también puede variar significativamente en una misma especie, o incluso en un mismo árbol, en función de la altura del fuste y de la distancia al centro del tronco.

Wood hardness

According to its hardness, wood is classified as:.

• - Hard woods: are those that come from slow-growing trees, so they are denser and withstand inclement weather better than soft woods. These woods generally come from deciduous trees, but they can also be evergreen, which take decades, and even centuries, to reach the sufficient degree of maturity to be cut and used in the production of furniture or beams for farmhouses or single-family homes. They are much more expensive than soft ones, because their slow growth causes them to be scarce, but they are much more attractive to build furniture with. They are also widely used to make wood carvings or any product in which quality solid wood is necessary. Trees that are classified within this type: beech, oak, walnut, maple "Acer (plant)"), hornbeam, teak, lapacho, etc.

• - Softwoods"): includes the wood of trees belonging to the order of conifers and other fast-growing ones. The great advantage they have with respect to hardwoods is their lightness and much lower price. They do not have as long a life as the hardwoods. The handling of softwoods is much simpler, although it has the disadvantage of producing a greater quantity of splinters. The lack of grain of this wood makes it less attractive, which is why it is almost always It is necessary to paint, varnish or stain it. Some widely used softwoods are: pine, fir, birch, poplar, cypress, balsa, etc.

Chestnut has a medium hardness and is very flexible, so it can be included in both groups.

The first wood product produced by man dates back to 5,255 BC. C.[12]​ Since then it has received various uses:.

• - Falling, cutting or felling: loggers with axes or electric or gasoline saws cut the tree, removing the branches, roots and bark so that it begins to dry. It is usually recommended that trees be cut in winter or fall. It is mandatory to replant more trees than those that were cut.

• - Transport: it is the second phase and it is in which the wood is transported from its cutting place to the sawmill and in this phase many things influence such as the orography and the existing infrastructure. Normally it is done by pulling with animals or machinery, but there are cases in which there is a river nearby and it is used to carry them. If there is a good current of water, the logs are released, being careful not to get stuck, but if there is little current, they are tied together, making rafts that are guided to where necessary.

• - Sawning: in this phase the wood is taken to sawmills. The sawmill divides the log into pieces, depending on the use that will be given to it later. They usually use different types of saws such as reciprocating, band, circular or roller saws. Some sawmills combine several of these techniques to improve production.

• - Drying: this is the most important process for the wood to be in good condition.

Chipboard or chipboard

It is obtained from small shavings or sawdust,[14]​ glued under pressure in a proportion of 85% shavings and 15% glue mainly. They are manufactured in different types depending on the size of their particles, their distribution throughout the board, as well as the adhesive used for their manufacture. In general, soft woods are used rather than hard ones due to the ease of working with them, since it is easier to press soft wood than hard wood.

Chipboards are stable materials with a uniform consistency, they have completely smooth surfaces and are suitable as bases for veneers. There is a wide range of these boards ranging from wood-based, paper or plastic laminates. Most chipboards are relatively brittle and have lower tensile strength than plywood because the others have perpendicularly overlapping layers of veneer that offer more strength.

This material is recommended for building all types of furniture (functional or artistic).

These boards are affected by excess humidity, presenting expansion in their thickness, an expansion that is not recovered with drying. It is not suitable for outdoors or for places in humid conditions, this type of wood swells immediately in minimal contact with water. In continuous humid conditions the boards swell to such an extent that they fall apart. However, models are manufactured with some resistance to humid conditions.

Although you should avoid placing screws along the edges of this type of sheet, if necessary, the diameter of the screws should not be greater than a quarter of the thickness of the board, to avoid cracking in the veneer on the faces.

In addition there are different types of chipboard:.

• - Oriented fiber chipboard, also known as OSB (oriented strand board*). Three-layer material made from large shavings, placed in transverse directions, simulating the structural effect of plywood. It is known by one of its trade names Aspenite.

• - Decorative chipboard that is manufactured with selected wood faces, plastic laminates or melamine. To finish the edges of these sheets, edge covers are sold that come with the same finish as the faces.

• - The three-layer agglomerate that has a core plate made up of large particles that are arranged between two layers of finer, high-density particles. Its surface is smoother and recommended for receiving paints.

• - The agglomerate of a layer that is made from particles of similar size distributed uniformly. Its surface is relatively coarse. It is recommended for veneer but not for painting directly on it.

Veneer boards

A solid wood board or sheet is relatively unstable and will experience contraction and expansion movements, mostly in the direction of the wood fibers, for this reason it is likely to suffer distortions. To counteract this effect, plywood is constructed by gluing the layers with the fibers transversely over each other, alternately. Most plywood is made up of an odd number of layers to form a balanced construction. The outer layers of a board are called faces and their quality is rated by a letter code that uses A as the best quality, B as intermediate and C as the lowest quality. The best quality side of a board is known as the "front side" and the lowest quality side is known as the "back side" or back. On the other hand, the central layer is called "soul." This is done to increase the strength of the board or piece being made.

Precomposed veneer is called a thin sheet of wood that is obtained by laminating a block of veneers starting from the edge of the block, that is, through the layers of wood pressed together. The strips of the original veneers are converted into the grain of the precomposed veneer, obtaining a grain that is perfectly straight or homogeneous.

By manipulating the contour of the sheets to be pressed, very varied configurations and very attractive appearances can be obtained. Some or all of the constituent sheets can be dyed before joining them, so that very striking appearances or colors are obtained.

Fiber boards

Fiberboards are constructed from wood that has been reduced to its basic fibrous elements and subsequently reconstituted to form a stable and homogeneous material. They are manufactured of different density depending on the pressure applied and the binder used in their manufacture.[15]​.

They can be divided into two main types, those of high density, which use the binders present in the wood itself, which in turn are divided into hard and semi-hard, and those of medium density, which use chemical agents foreign to the wood as a binder for the fibers.

They are divided into several types:[15]​.

• - Hard fiber boards.

• - Semi-hard boards, among which are low-density boards (DB) that range between 6 mm and 12 mm and are used as coverings and for control panels, and high-density boards (DA), which are used for interior coverings.

• - Medium density fiber boards characterized by having both sides smooth and manufactured using a dry process. The fibers are glued together using a synthetic resin adhesive. These boards can be worked as if they were solid wood. They make an excellent base for veneers and take "Paint (material)" paints well. They are manufactured in thicknesses between 3 mm and 32 mm.

• - Fiber boards.

• - Pavements: Wood has been used as a material in wooden pavements since ancient times, due to its ductility and insulation, but it was not until the century that it spread throughout Europe. Examples include parquet, Cosmatesque flooring and marquetry.

• - Kitchenware: crockery, cutlery.

• - Carpentry.

• - Medicine.

Wood deterioration is a process that alters its characteristics. In broad terms, it can be attributed to two primary causes:

• - biotic (living) agents.

• - abiotic (non-living) agents (can be physical, chemical, atmospheric).

In most cases, wood deterioration is a continuum, where the degrading actions are one or more agents that alter the characteristics of the wood to the degree required for other agents to attack. The inspector's familiarity with spoilage agents is one of the most important aids to effective inspection. With this knowledge, the inspection can be approached with a careful view of the processes involved in the damage and the factors that favor or inhibit its development.

• - Annex:Woods").

Literature

• - The online version is a partial view of the book.

• - Wikimedia Commons hosts a multimedia gallery on Wood.

• - Wiktionary has definitions and other information about wood.