Los insectos están entre los organismos más comunes en la Tierra, y muchas de sus especies poseen la capacidad de utilizar la madera para abrigo o alimento. De los 26 órdenes de insectos, 6 causan daño a la madera. Termitas (Isoptera), escarabajos (Coleoptera), abejas, avispas y las hormigas (himenópteros) son las causas primarias de la mayoría de la destrucción en la madera.

El ataque del insecto es evidente, generalmente, por aparición de túneles o cavidades en la madera, que contienen a menudo polvo o aserrín (heces del insecto) de madera. La presencia de polvo al pie de la madera o aserrín sobre la superficie de la madera son muestras de un ataque.

Termites

There are 2000 species of termites that are distributed in areas where the average annual temperature is 10 °C or higher. In some cases, termites prolong their progression in cooler climates by living in warm man-made structures. They attack most wood species. Termites are social insects, organized into a series of classes that perform specific functions. The leader of the colony is a queen whose sole purpose is to lay eggs. The queen is protected by the soldiers and is strengthened and fed by the workers, who also build the nest and cause damage to the wood. Like all creatures, termites have certain requirements, including high moisture content wood, a convenient food source, a high level of carbon dioxide, and oxygen. Termite colonies range in number up to a million or more.

They implicitly attack any available wood, but require a source of moisture and typically a nest in the ground. They have developed the ability to attack wood above ground by building earth tubes that protect them from light and carry moisture to the wood. Wood damaged by subterranean termites have numerous tunnels through the spring wood but there is no exit hole to the surface to indicate the presence of termites. Often, a sharp tap on the surface of the wood will reveal that there is only a thin plate of wood debris. Termites' underground tunnels fill with a mixture of debris and feces, giving them a dirty appearance.

They are common in the Pacific northwest, although a group is found in the more arid southwest. The most common dampwood species is found along the Pacific coast from northern California to British Columbia. Like subterranean termites, dampwood species need wood that is very wet, and their attack is often associated with damage. These insects are a problem for freshly cut lumber, utility poles, and any untreated wood that is in contact with the ground. The tunnels made by damp wood termites are quite large; like the subterranean species, they tend to avoid the harder summer wood. The tunnels often contain small amounts of sawdust, however the appearance of the wood is somewhat cleaner than that which is attacked by the underground species. Dampwood termite attack can be prevented or stopped by removing the source of moisture or using preservative-treated wood in situations requiring contact with soil.

They are differentiated from subterranean dampwood termites by their ability to attack wood that is extremely dry (5 to 6 percent moisture content). As a result, the attack of dry wood termites is not on pieces that have to be in contact with the ground and are also far from visible sources of moisture. Wood damage from these insects is long smooth tunnels that are free of sawdust or debris. Furthermore, there is no variation in attacks between spring wood and summer wood. Drywood termites frequently clean the nest by chewing on the tunnel surfaces, pounding and dislodging debris, in which infected wood accumulates below. Although the tunnels are resealed, the presence of debris beneath the opening is a good sign of attack. In general, clusters of infections are found in a geographic area, and prevention poses some difficulty. While an infection occurs, the use of structural fumigation has become widespread because it is effective. Fortunately, the drywood termite is confined to a relatively small geographic region.

Beetles

(Coleoptera) represent the largest order of insects that cause substantial damage to wood. Many beetles attack only living trees or cut fresh wood, but are easily combated as their damage can be found during inspection. The larvae of many of these beetles are called woodworm or quera.

They are insects whose larvae attack wood, leaving behind a series of small tunnels packed with excrement. The three families of wood-pulverizing beetles are anobids, bostrichids, and lyctids. These insects cause serious damage to wood and are a particular problem in museums, where wooden artifacts can go unnoticed for long periods. Anobids and bostrichids attack dead branches in damp wood but also attack untreated wood. The damage is worsened by adults that emerge by reinfecting the same piece. of wood.

It is found throughout the world in hardwoods and attacks those with a moisture content above 8 percent. The larvae of these beetles make the tunnel, and also expel the excrement out of the wood. These excrements accumulate at the foot of the affected wood and are a good sign of sprayer infection. The use of preservative treatments on the wood will prevent lyctide infection. However, wood pulverizer beetle attack can become a problem where untreated wood is used in older existing structures.

Also called flathead or metal wood borers, they are almost entirely dependent on trees completing their life cycle. They cause significant damage by attacking living trees, leaving damage that may be evident in lumber or other wood products. This beetle lays its eggs on the bark surfaces or in wounds of the tree. Over the course of their 1 to 3 year life cycles, larvae extensively tunnel in wood, leaving galleries packed tightly with their excrement. The mature larval pupae and the adult chew an escape through a hole forming the exit. In addition to the species that attack live trees, one species, the golden buprestid (Buprestis aurulenta) is capable of attacking live Douglas fir. This beetle causes serious damage to utility poles, where these attacks are often associated with extensive damage.

They include a number of wood degraders that generally have antennae longer than their bodies. They attack wood in all conditions, depending on the species, and cause substantial damage. Some, such as the sugar maple borer and the cottonwood borer, attack only living trees, killing them and reducing the value of the wood.

Dendroctonus ponderosae pierces the pine bark or its wood in recently cut specimens, rapidly degrading the wood.

An interesting attacker of greenwood is the powerful borer, whose larvae attack Douglas fir and pine, producing tunnels nearly an inch in diameter. Although this larva can complete its development in sawn wood, it does not reinfect previously attacked wood.

In addition to longhorn beetles that attack life in recently harvested trees, several species cause damage to serviced timber. Another species, the old house borer, is one of the most destructive wood borers and prefers dry coniferous wood.

carpenter ants

They differ from the insects previously described in that they use wood as shelter rather than food. They are social insects with a complex organization that revolves around the queen. To sustain the colony and raise their young, worker carpenter ants must cover long distances from their nest to obtain food, which may consist of insect secretions and sugary sources. As the colony grows from the original queen by about 100,000 members, the workers gradually enlarge their nest, causing serious internal damage to the wood.

carpenter bees

Like ants, Carpenter Bees use wood only for shelter and to raise their young. In this process, they make a tunnel along the fibers of coniferous woods, creating galleries 13 to 46 cm long by 0.8 to 1 cm wide. Carpenter bees appear remarkably similar to bumblebees but differ slightly in coloration. They are not common, but when infection occurs, the damage can be serious.[2]​

Adults of this species tunnel into wood and lay their eggs in individual cells that are supplied with food for growing larvae. Adults emerge and can reinfect the wood. These insects have also been found attacking wood treated with inorganic arsenicals in soil retentions.

Gran variedad de moluscos y crustáceos atacan a la madera de barcos, pontones, muelles "Muelle (construcción)"), puentes, etc. Son conocidos como perforadores marinos.

Cuando las subestructuras de la madera están situadas en aguas saladas, el daño severo puede ocurrir por el ataque de los perforadores marinos. Los perforadores marinos que causan el daño en la madera, se clasifican en tres grupos basados sobre su morfología y patrón de ataque a la madera: polas, gusanos de barco "Broma (molusco)") y Limnoria.

Poles

They are mollusks, which take refuge in wood and filter food from the surrounding water. They begin life as tiny, free-swimming larvae that eventually settle on a favorable wood surface until they become permanently established. The polas grow approximately 64 mm long and leave an entrance hole in the surface of the wood about 6 mm in diameter. While polas live in wood, the surface eventually weakens and tends to break under the action of the wave. Internal damage is usually identifiable by the characteristic pear shape. Eventually, the area of ​​the wood decreases to the point where it fails. The attack can be prevented with the use of creosote in the wood; However, other wood-degrading organisms in tropical environments are resistant to creosote so dual treatment with creosote and a floating inorganic arsenic is required. In temperate water rocks, burrowing polas also cause damage to concrete structures.

Shipworms or jokes

They are long, mollusks cause internal damage to the wood while leaving only a small hole in the surface as evidence of their attack. Like polas, shipworms begin life as small, free-swimming larvae, then begin their sedentary life inhabiting wood. In the century ship captains exploited this portion of the life cycle by sailing their infected wooden ships in fresh water where trapped shipworms died from lack of salt.

While shipworms settle in the wood, with the caps of their heads they begin to scrape the wood, making a tunnel with a characteristic white coating. The shipworm gradually enlarges the tunnel within the wood, but the initial hole rarely enlarges beyond 15 mm in diameter. For the safety of their burrow in wood, shipworms extend a pair of feathery siphons into the surrounding water. These siphons function as food, oxygen and waste exchangers. At any sign of danger the siphons are contracted and the superficial hole is covered by a hardened platform that protects the organism against attack. Protecting the deck allows the shipworm to survive on the wood out of the water for 7 to 10 days. The small size of the surface hole and the presence of the platform makes visual detection of internal shipworm attack difficult, but advances in acoustic detection have improved the prospects of detecting infections before substantial damage occurs.

Limnoria

They are mobile crustaceans that differ from shipworms and poleworms in their ability to move from one stretch of wood to another during their life cycle. There are 20 species of Limnoria that attack wood in marine waters, but only 3 cause significant damage. Two of these species are capable of attacking only untreated wood, but the other species attacks even creosote-treated wood. In some cases, specimens of this species have been removed from the creosote wood and the preservative could literally be squeezed out of their bodies, yet they continue to attack the wood.

Limnoria damage wood with their small diameter burrow (30 mm), which tunnels near the surface. Although the damage is minimal, the continued removal of wood weakened by wave action exposes new wood to attack. Eventually, the wood area is reduced to the point where the structure fails or must be replaced. A classic example of the Limnoria attack is the hourglass shape that seriously attacks the piece taken over the tidal zone; However, attack can and does extend to the mud line, if oxygen and salinity conditions are suitable.

Aunque el deterioro de la madera se ve tradicionalmente como proceso biológico, la madera se puede también degradar por los agentes físicos y químicos. Los agentes son generalmente de actuar lento, pero pueden llegar a ser absolutamente serios en localizaciones específicas. Los agentes físicos y químicos incluyen abrasión mecánica o impacto, luz ultravioleta, subproductos de corrosión del metal, y ácidos o bases fuertes. El daño por los agentes físicos se puede confundir por ataque biótico, pero la carencia de muestras visibles de los hongos, insectos, o perforadores marinos, más el aspecto general de la madera, puede advertir al inspector por la naturaleza del daño. Aunque destructivo en sus derechos propios, los agentes físicos pueden también dañar el tratamiento de preservación, y exponer a la madera no tratada al ataque de los agentes bióticos.

mechanical damage

They are probably the most significant physical agent of wooden bridge deterioration. It is caused by a number of factors and considerably various in their effects on the structure. The most common mechanical damage is abrasion due to vehicles, which produces worn or damaged surfaces and reduces the section of the wood. Obvious examples of this damage occur in the bridge deck area where abrasion results in surface degradation. More severe mechanical damage can be caused by long-term exposure to vehicle overloads, foundation installations, cataclysms or ice floes in a canal current.

ultraviolet light

It is the origin of the most visible deterioration in wood, resulting from the ultraviolet action of the sun that chemically degrades the lignin near the surface of the wood. Ultraviolet degradation typically causes light woods to darken and dark woods to become darker, but this damage penetrates only a small depth below the surface.

Damaged wood is slightly weaker, but the low depth of the damage means that it has little influence on the strength unless the piece of wood where it is damaged is removed, eventually reducing the dimensions of the piece.

Corrosion

It can be revealing in some situations, particularly in marine environments where galvanic cells due to the metals and salt water that form accelerate corrosion. Degradation begins when moisture in the wood reacts with iron in a bonding mechanism, releasing ferric ions alternately, deteriorating the cell wall of the wood.

As corrosion progresses the bonding mechanism becomes an electrolytic cell with an acidic end (anode) and an alkaline end (cathode). Although the cathode conditions are not severe, the acidity of the anode causes hydrolysis of cellulose and seriously reduces the strength of the wood in the affected area. The wood attacked in this way is often dark and appears soft. In many species of wood, discoloration also occurs where the metal comes into contact with the core of the wood.

In addition to the deterioration caused by corrosion, the high humidity conditions associated with this damage may initially favor the development of the rot fungus. As corrosion progresses, the toxicity of the metal ions and the low pH in the wood eventually eliminates the fungus from the affected area, although rot may continue at some distance from the bonding mechanism. The effect of metal corrosion on wood can be limited by using galvanized or non-metallic joints.

Chemical degradation

In rare cases, the presence of strong acids or bases can cause substantial damage to the wood. Strong bases attack hemicellulose and lignin, leaving the wood a discolored white color. Strong acids attack cellulose and hemicellulose, causing weight and strength losses. Wood damaged by acid is dark in color and looks similar to wood damaged by fire. Strong chemicals will not normally come into contact with, for example, a wooden bridge unless accidental spills occur.

Los insectos están entre los organismos más comunes en la Tierra, y muchas de sus especies poseen la capacidad de utilizar la madera para abrigo o alimento. De los 26 órdenes de insectos, 6 causan daño a la madera. Termitas (Isoptera), escarabajos (Coleoptera), abejas, avispas y las hormigas (himenópteros) son las causas primarias de la mayoría de la destrucción en la madera.

El ataque del insecto es evidente, generalmente, por aparición de túneles o cavidades en la madera, que contienen a menudo polvo o aserrín (heces del insecto) de madera. La presencia de polvo al pie de la madera o aserrín sobre la superficie de la madera son muestras de un ataque.

Termites

There are 2000 species of termites that are distributed in areas where the average annual temperature is 10 °C or higher. In some cases, termites prolong their progression in cooler climates by living in warm man-made structures. They attack most wood species. Termites are social insects, organized into a series of classes that perform specific functions. The leader of the colony is a queen whose sole purpose is to lay eggs. The queen is protected by the soldiers and is strengthened and fed by the workers, who also build the nest and cause damage to the wood. Like all creatures, termites have certain requirements, including high moisture content wood, a convenient food source, a high level of carbon dioxide, and oxygen. Termite colonies range in number up to a million or more.

They implicitly attack any available wood, but require a source of moisture and typically a nest in the ground. They have developed the ability to attack wood above ground by building earth tubes that protect them from light and carry moisture to the wood. Wood damaged by subterranean termites have numerous tunnels through the spring wood but there is no exit hole to the surface to indicate the presence of termites. Often, a sharp tap on the surface of the wood will reveal that there is only a thin plate of wood debris. Termites' underground tunnels fill with a mixture of debris and feces, giving them a dirty appearance.

They are common in the Pacific northwest, although a group is found in the more arid southwest. The most common dampwood species is found along the Pacific coast from northern California to British Columbia. Like subterranean termites, dampwood species need wood that is very wet, and their attack is often associated with damage. These insects are a problem for freshly cut lumber, utility poles, and any untreated wood that is in contact with the ground. The tunnels made by damp wood termites are quite large; like the subterranean species, they tend to avoid the harder summer wood. The tunnels often contain small amounts of sawdust, however the appearance of the wood is somewhat cleaner than that which is attacked by the underground species. Dampwood termite attack can be prevented or stopped by removing the source of moisture or using preservative-treated wood in situations requiring contact with soil.

They are differentiated from subterranean dampwood termites by their ability to attack wood that is extremely dry (5 to 6 percent moisture content). As a result, the attack of dry wood termites is not on pieces that have to be in contact with the ground and are also far from visible sources of moisture. Wood damage from these insects is long smooth tunnels that are free of sawdust or debris. Furthermore, there is no variation in attacks between spring wood and summer wood. Drywood termites frequently clean the nest by chewing on the tunnel surfaces, pounding and dislodging debris, in which infected wood accumulates below. Although the tunnels are resealed, the presence of debris beneath the opening is a good sign of attack. In general, clusters of infections are found in a geographic area, and prevention poses some difficulty. While an infection occurs, the use of structural fumigation has become widespread because it is effective. Fortunately, the drywood termite is confined to a relatively small geographic region.

Beetles

(Coleoptera) represent the largest order of insects that cause substantial damage to wood. Many beetles attack only living trees or cut fresh wood, but are easily combated as their damage can be found during inspection. The larvae of many of these beetles are called woodworm or quera.

They are insects whose larvae attack wood, leaving behind a series of small tunnels packed with excrement. The three families of wood-pulverizing beetles are anobids, bostrichids, and lyctids. These insects cause serious damage to wood and are a particular problem in museums, where wooden artifacts can go unnoticed for long periods. Anobids and bostrichids attack dead branches in damp wood but also attack untreated wood. The damage is worsened by adults that emerge by reinfecting the same piece. of wood.

It is found throughout the world in hardwoods and attacks those with a moisture content above 8 percent. The larvae of these beetles make the tunnel, and also expel the excrement out of the wood. These excrements accumulate at the foot of the affected wood and are a good sign of sprayer infection. The use of preservative treatments on the wood will prevent lyctide infection. However, wood pulverizer beetle attack can become a problem where untreated wood is used in older existing structures.

Also called flathead or metal wood borers, they are almost entirely dependent on trees completing their life cycle. They cause significant damage by attacking living trees, leaving damage that may be evident in lumber or other wood products. This beetle lays its eggs on the bark surfaces or in wounds of the tree. Over the course of their 1 to 3 year life cycles, larvae extensively tunnel in wood, leaving galleries packed tightly with their excrement. The mature larval pupae and the adult chew an escape through a hole forming the exit. In addition to the species that attack live trees, one species, the golden buprestid (Buprestis aurulenta) is capable of attacking live Douglas fir. This beetle causes serious damage to utility poles, where these attacks are often associated with extensive damage.

They include a number of wood degraders that generally have antennae longer than their bodies. They attack wood in all conditions, depending on the species, and cause substantial damage. Some, such as the sugar maple borer and the cottonwood borer, attack only living trees, killing them and reducing the value of the wood.

Dendroctonus ponderosae pierces the pine bark or its wood in recently cut specimens, rapidly degrading the wood.

An interesting attacker of greenwood is the powerful borer, whose larvae attack Douglas fir and pine, producing tunnels nearly an inch in diameter. Although this larva can complete its development in sawn wood, it does not reinfect previously attacked wood.

In addition to longhorn beetles that attack life in recently harvested trees, several species cause damage to serviced timber. Another species, the old house borer, is one of the most destructive wood borers and prefers dry coniferous wood.

carpenter ants

They differ from the insects previously described in that they use wood as shelter rather than food. They are social insects with a complex organization that revolves around the queen. To sustain the colony and raise their young, worker carpenter ants must cover long distances from their nest to obtain food, which may consist of insect secretions and sugary sources. As the colony grows from the original queen by about 100,000 members, the workers gradually enlarge their nest, causing serious internal damage to the wood.

carpenter bees

Like ants, Carpenter Bees use wood only for shelter and to raise their young. In this process, they make a tunnel along the fibers of coniferous woods, creating galleries 13 to 46 cm long by 0.8 to 1 cm wide. Carpenter bees appear remarkably similar to bumblebees but differ slightly in coloration. They are not common, but when infection occurs, the damage can be serious.[2]​

Adults of this species tunnel into wood and lay their eggs in individual cells that are supplied with food for growing larvae. Adults emerge and can reinfect the wood. These insects have also been found attacking wood treated with inorganic arsenicals in soil retentions.

Gran variedad de moluscos y crustáceos atacan a la madera de barcos, pontones, muelles "Muelle (construcción)"), puentes, etc. Son conocidos como perforadores marinos.

Cuando las subestructuras de la madera están situadas en aguas saladas, el daño severo puede ocurrir por el ataque de los perforadores marinos. Los perforadores marinos que causan el daño en la madera, se clasifican en tres grupos basados sobre su morfología y patrón de ataque a la madera: polas, gusanos de barco "Broma (molusco)") y Limnoria.

Poles

They are mollusks, which take refuge in wood and filter food from the surrounding water. They begin life as tiny, free-swimming larvae that eventually settle on a favorable wood surface until they become permanently established. The polas grow approximately 64 mm long and leave an entrance hole in the surface of the wood about 6 mm in diameter. While polas live in wood, the surface eventually weakens and tends to break under the action of the wave. Internal damage is usually identifiable by the characteristic pear shape. Eventually, the area of ​​the wood decreases to the point where it fails. The attack can be prevented with the use of creosote in the wood; However, other wood-degrading organisms in tropical environments are resistant to creosote so dual treatment with creosote and a floating inorganic arsenic is required. In temperate water rocks, burrowing polas also cause damage to concrete structures.

Shipworms or jokes

They are long, mollusks cause internal damage to the wood while leaving only a small hole in the surface as evidence of their attack. Like polas, shipworms begin life as small, free-swimming larvae, then begin their sedentary life inhabiting wood. In the century ship captains exploited this portion of the life cycle by sailing their infected wooden ships in fresh water where trapped shipworms died from lack of salt.

While shipworms settle in the wood, with the caps of their heads they begin to scrape the wood, making a tunnel with a characteristic white coating. The shipworm gradually enlarges the tunnel within the wood, but the initial hole rarely enlarges beyond 15 mm in diameter. For the safety of their burrow in wood, shipworms extend a pair of feathery siphons into the surrounding water. These siphons function as food, oxygen and waste exchangers. At any sign of danger the siphons are contracted and the superficial hole is covered by a hardened platform that protects the organism against attack. Protecting the deck allows the shipworm to survive on the wood out of the water for 7 to 10 days. The small size of the surface hole and the presence of the platform makes visual detection of internal shipworm attack difficult, but advances in acoustic detection have improved the prospects of detecting infections before substantial damage occurs.

Limnoria

They are mobile crustaceans that differ from shipworms and poleworms in their ability to move from one stretch of wood to another during their life cycle. There are 20 species of Limnoria that attack wood in marine waters, but only 3 cause significant damage. Two of these species are capable of attacking only untreated wood, but the other species attacks even creosote-treated wood. In some cases, specimens of this species have been removed from the creosote wood and the preservative could literally be squeezed out of their bodies, yet they continue to attack the wood.

Limnoria damage wood with their small diameter burrow (30 mm), which tunnels near the surface. Although the damage is minimal, the continued removal of wood weakened by wave action exposes new wood to attack. Eventually, the wood area is reduced to the point where the structure fails or must be replaced. A classic example of the Limnoria attack is the hourglass shape that seriously attacks the piece taken over the tidal zone; However, attack can and does extend to the mud line, if oxygen and salinity conditions are suitable.

Aunque el deterioro de la madera se ve tradicionalmente como proceso biológico, la madera se puede también degradar por los agentes físicos y químicos. Los agentes son generalmente de actuar lento, pero pueden llegar a ser absolutamente serios en localizaciones específicas. Los agentes físicos y químicos incluyen abrasión mecánica o impacto, luz ultravioleta, subproductos de corrosión del metal, y ácidos o bases fuertes. El daño por los agentes físicos se puede confundir por ataque biótico, pero la carencia de muestras visibles de los hongos, insectos, o perforadores marinos, más el aspecto general de la madera, puede advertir al inspector por la naturaleza del daño. Aunque destructivo en sus derechos propios, los agentes físicos pueden también dañar el tratamiento de preservación, y exponer a la madera no tratada al ataque de los agentes bióticos.

mechanical damage

They are probably the most significant physical agent of wooden bridge deterioration. It is caused by a number of factors and considerably various in their effects on the structure. The most common mechanical damage is abrasion due to vehicles, which produces worn or damaged surfaces and reduces the section of the wood. Obvious examples of this damage occur in the bridge deck area where abrasion results in surface degradation. More severe mechanical damage can be caused by long-term exposure to vehicle overloads, foundation installations, cataclysms or ice floes in a canal current.

ultraviolet light

It is the origin of the most visible deterioration in wood, resulting from the ultraviolet action of the sun that chemically degrades the lignin near the surface of the wood. Ultraviolet degradation typically causes light woods to darken and dark woods to become darker, but this damage penetrates only a small depth below the surface.

Damaged wood is slightly weaker, but the low depth of the damage means that it has little influence on the strength unless the piece of wood where it is damaged is removed, eventually reducing the dimensions of the piece.

Corrosion

It can be revealing in some situations, particularly in marine environments where galvanic cells due to the metals and salt water that form accelerate corrosion. Degradation begins when moisture in the wood reacts with iron in a bonding mechanism, releasing ferric ions alternately, deteriorating the cell wall of the wood.

As corrosion progresses the bonding mechanism becomes an electrolytic cell with an acidic end (anode) and an alkaline end (cathode). Although the cathode conditions are not severe, the acidity of the anode causes hydrolysis of cellulose and seriously reduces the strength of the wood in the affected area. The wood attacked in this way is often dark and appears soft. In many species of wood, discoloration also occurs where the metal comes into contact with the core of the wood.

In addition to the deterioration caused by corrosion, the high humidity conditions associated with this damage may initially favor the development of the rot fungus. As corrosion progresses, the toxicity of the metal ions and the low pH in the wood eventually eliminates the fungus from the affected area, although rot may continue at some distance from the bonding mechanism. The effect of metal corrosion on wood can be limited by using galvanized or non-metallic joints.

Chemical degradation

In rare cases, the presence of strong acids or bases can cause substantial damage to the wood. Strong bases attack hemicellulose and lignin, leaving the wood a discolored white color. Strong acids attack cellulose and hemicellulose, causing weight and strength losses. Wood damaged by acid is dark in color and looks similar to wood damaged by fire. Strong chemicals will not normally come into contact with, for example, a wooden bridge unless accidental spills occur.