1 unit d: forest products lesson 4: protecting and preserving wood

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Unit D: Forest ProductsUnit D: Forest Products

Lesson 4: Protecting and Lesson 4: Protecting and Preserving WoodPreserving Wood

TermsTerms

Coal-tar creosoteCoal-tar creosote Cold-soakingCold-soaking Double-diffusionDouble-diffusion HeartwoodHeartwood

Hot-cold bathHot-cold bath SapwoodSapwood Surface checkSurface check

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What causes wood to deteriorate?What causes wood to deteriorate?Like other materials, wood Like other materials, wood

deteriorates as a result of interaction deteriorates as a result of interaction with the environment.with the environment.

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What causes wood to deteriorate?What causes wood to deteriorate?

Wood exposed to fungi, damp or moist Wood exposed to fungi, damp or moist places, or certain insects will deteriorate.places, or certain insects will deteriorate.• Wood products placed near the surface of Wood products placed near the surface of

the ground are very susceptible to decay the ground are very susceptible to decay and to destruction by insects.and to destruction by insects.

• In general, all wood contacting the ground In general, all wood contacting the ground or exposed to weather should be treated or exposed to weather should be treated with a preservative.with a preservative.

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Using a preservative is even more Using a preservative is even more important in regions where high important in regions where high rainfall and mild climate are factors.rainfall and mild climate are factors.

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When planning a project made of When planning a project made of wood or that will utilize wood, wood or that will utilize wood, following accepted precautions will following accepted precautions will reduce the chances that the wood reduce the chances that the wood will deteriorate prematurely.will deteriorate prematurely.• Consider conditions that present Consider conditions that present

potential decay or insect problems.potential decay or insect problems.

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Design and treat new construction Design and treat new construction to protect wood from moisture, to protect wood from moisture, decay hazards, and insects.decay hazards, and insects.

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Use treated wood in constructions Use treated wood in constructions where wood cannot be kept at least where wood cannot be kept at least 45 centimeters above the surface of 45 centimeters above the surface of the ground and protected from the ground and protected from excessive moisture. excessive moisture.

Treat exposed large load-bearing Treat exposed large load-bearing beams with preservative.beams with preservative.

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Recognize that preservative is essential Recognize that preservative is essential where wood in permanent structures is where wood in permanent structures is in contact with the ground.in contact with the ground.

When wood decay is detected, When wood decay is detected, immediately remove moisture from the immediately remove moisture from the wood so decay does not worsen. wood so decay does not worsen. • Decay causing fungi grow even when there Decay causing fungi grow even when there

is only a little moisture on the surface of is only a little moisture on the surface of wood cells.wood cells.

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What are the commercial and What are the commercial and noncommercial wood preservatives?noncommercial wood preservatives?

The purpose of treating wood is to The purpose of treating wood is to protect it against insects and decay protect it against insects and decay organisms.organisms.• Wood that is commercially pressure Wood that is commercially pressure

treated with a good preservative can treated with a good preservative can be expected to give the most be expected to give the most dependable service.dependable service.

1111Pressure treated lumber

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Pressure treatment requires Pressure treatment requires expensive equipment and highly expensive equipment and highly technical skills.technical skills.

The wood to be treated is placed in The wood to be treated is placed in a steel cylinder and sealed. a steel cylinder and sealed. • A preservative is pumped into the A preservative is pumped into the

cylinder, and pressure and/or vacuum cylinder, and pressure and/or vacuum is applied so that the wood takes up is applied so that the wood takes up the desired amount of preservative.the desired amount of preservative.

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Wood can be treated at home with Wood can be treated at home with good results by proper use of good results by proper use of recognized toxic preservative.recognized toxic preservative.

Good preservatives applied poorly Good preservatives applied poorly or poor preservatives applied or poor preservatives applied carefully are of little value.carefully are of little value.• A preservative protects wood from A preservative protects wood from

dangerous fungi and insects.dangerous fungi and insects.

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A good preservative must do a number A good preservative must do a number things.things.

It must penetrate the wood to sufficient It must penetrate the wood to sufficient depth to form an exterior shell of depth to form an exterior shell of poisonous wood that will prevent attacks poisonous wood that will prevent attacks by fungi and insects, even in surface by fungi and insects, even in surface checks that may later develop.checks that may later develop.• A surface check is a crack, usually formed A surface check is a crack, usually formed

in the drying-out process.in the drying-out process.

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It must retain its toxic effect under It must retain its toxic effect under field conditions for a number of field conditions for a number of years.years.

It should not easily leach out of the It should not easily leach out of the wood while in service.wood while in service.

It must not be flammable or It must not be flammable or injurious to the wood, or corrode injurious to the wood, or corrode metal.metal.

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It should not be dangerous to It should not be dangerous to animals and humans when used in animals and humans when used in normal concentrations.normal concentrations.• Protective clothing and accessories, Protective clothing and accessories,

and eyeware should be worn to guard and eyeware should be worn to guard against injury from spills and spatters. against injury from spills and spatters.

• It must be handled safely and applied It must be handled safely and applied according to the manufacturer’s label.according to the manufacturer’s label.

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Lumber treated with preservatives Lumber treated with preservatives should be handled cautiously. should be handled cautiously.

Always wear skin and eye protection Always wear skin and eye protection when handling treated lumber. when handling treated lumber.

Protection from breathing the Protection from breathing the sawdust when cutting treated sawdust when cutting treated lumber is necessary.lumber is necessary.

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Treated lumber should not be used Treated lumber should not be used for interior applications.for interior applications.

Treated lumber should be sealed Treated lumber should be sealed with paint or polyurethane after with paint or polyurethane after construction. construction. • To prevent the preservative from To prevent the preservative from

being leached out.being leached out.

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Lumber treated with arsenic-based Lumber treated with arsenic-based wood preservatives such as chromated wood preservatives such as chromated copper arsenate (CCA) has been copper arsenate (CCA) has been banned for residential use as a wood banned for residential use as a wood preservative by the EPA because preservative by the EPA because arsenic is known to cause cancer in arsenic is known to cause cancer in humans and was phased out of humans and was phased out of production in January 2004.production in January 2004.

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Because of the wide spread use of Because of the wide spread use of CCA-treated lumber, certain CCA-treated lumber, certain precautions should be followed to precautions should be followed to reduce exposure to arsenic.reduce exposure to arsenic.• Seal wood annually with standard Seal wood annually with standard

wood treatments.wood treatments.

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Wash your skin when and where Wash your skin when and where any contact has been made and any contact has been made and especially before eating.especially before eating.

Do not store toys or tools in treated Do not store toys or tools in treated lumber. lumber. • Arsenic leached from the lumber will Arsenic leached from the lumber will

accumulate on anything around it, accumulate on anything around it, including the soil.including the soil.

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Do not allow children or pets to have Do not allow children or pets to have access to this type of treated access to this type of treated lumber.lumber.

Cover a CCA-treated outside table Cover a CCA-treated outside table with a tablecloth before using.with a tablecloth before using.

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Preservatives such as coal-tar Preservatives such as coal-tar creosote, solutions of creosote creosote, solutions of creosote mixed with other toxic chemicals, mixed with other toxic chemicals, pentachlorophenol (penta) solutions, pentachlorophenol (penta) solutions, and water-borne materials and water-borne materials containing one or more compounds containing one or more compounds of copper, zinc, fluorine, and of copper, zinc, fluorine, and chromium bring good results. chromium bring good results.

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However, coal-tar creosote and However, coal-tar creosote and pentachlorophenol are only pentachlorophenol are only available for purchase and use by available for purchase and use by properly licensed users.properly licensed users.

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What are the naturally durable woods?What are the naturally durable woods?

There are several naturally durable There are several naturally durable woods.woods.

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The natural durability of a given The natural durability of a given wood is determined by what part of wood is determined by what part of the tree it is taken from.the tree it is taken from.

The sapwood of trees is not durable The sapwood of trees is not durable when it is in contact with the soil. when it is in contact with the soil.

Sapwood is the light-colored wood Sapwood is the light-colored wood near the outer portion of the tree.near the outer portion of the tree.

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Sapwood is composed of living cells Sapwood is composed of living cells and conducts water and minerals to and conducts water and minerals to the tree crown.the tree crown.

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Heartwood, the dark inner core of Heartwood, the dark inner core of the tree, is composed on non-living the tree, is composed on non-living cells and naturally resists decay cells and naturally resists decay better than the sapwood.better than the sapwood.

The heartwood is more resistant in The heartwood is more resistant in some species than in others.some species than in others.

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The heartwood of several species The heartwood of several species is considered naturally durable and, is considered naturally durable and, though untreated, can be used in though untreated, can be used in areas where wood comes in contact areas where wood comes in contact with the ground.with the ground.

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Black locust, black walnut, osage-Black locust, black walnut, osage-orange, catalpa, cedar, chestnut, orange, catalpa, cedar, chestnut, chinkapin, juniper, lighter or pitchy pine, chinkapin, juniper, lighter or pitchy pine, pacific yew, red mulberry, sassafras and pacific yew, red mulberry, sassafras and white oak species are considered white oak species are considered naturally durable.naturally durable.

Black locust, lighter pine, red mulberry, Black locust, lighter pine, red mulberry, pacific yew and osage-orange are pacific yew and osage-orange are considered the most durable.considered the most durable.

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What preservatives are used for wood?What preservatives are used for wood?

Wood preservatives are used to Wood preservatives are used to preserve or extend the life of wood preserve or extend the life of wood and wood products.and wood products.

Wood preservatives can be divided Wood preservatives can be divided into two groups: preservative oils into two groups: preservative oils and water-borne salts.and water-borne salts.

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Preservative oils have higher Preservative oils have higher resistance to leaching than do salts resistance to leaching than do salts and are more suitable for outdoor and are more suitable for outdoor exposure.exposure.

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The following are examples of The following are examples of preservative oils.preservative oils.• Coal-tar creosote, the most widely Coal-tar creosote, the most widely

used industrial preservative, is a used industrial preservative, is a brownish or black oil made by distilling brownish or black oil made by distilling coal tar. coal tar. It is practically insoluble in water and has It is practically insoluble in water and has

proven to be the best preservative for proven to be the best preservative for wood that will come in contact with wood that will come in contact with water.water.

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Coal-tar creosotes for non-pressure Coal-tar creosotes for non-pressure treatments are creosotes known as treatments are creosotes known as crystal-free coal-tar creosotes. crystal-free coal-tar creosotes.

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In the process of manufacture, the In the process of manufacture, the crystal forming chemicals have been crystal forming chemicals have been removed. removed.

Since the oil flows freely at ordinary Since the oil flows freely at ordinary temperatures, creosotes of this type temperatures, creosotes of this type are used when brush or spray are used when brush or spray applications are desired.applications are desired.

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Creosote mixtures are made from Creosote mixtures are made from coal tar and are usually so toxic to coal tar and are usually so toxic to fungi that they can be diluted up to fungi that they can be diluted up to 50 percent or more with other oils to 50 percent or more with other oils to lower the cost of using the lower the cost of using the preservatives.preservatives.

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Other creosotes include wood-tar, Other creosotes include wood-tar, water-gas-tar, and oil-tar. water-gas-tar, and oil-tar. • They have wood-preserving properties They have wood-preserving properties

when of good quality and properly when of good quality and properly used.used.

Coal tar alone is not a good Coal tar alone is not a good preserver. preserver. • It is not very poisonous to fungi and it It is not very poisonous to fungi and it

does not penetrate wood very well.does not penetrate wood very well.

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Of the chlorinated phenols, Of the chlorinated phenols, pentachlorophenol or penta, has pentachlorophenol or penta, has gained wide acceptance as an gained wide acceptance as an effective wood preservative in cold effective wood preservative in cold soaking and in the hot-cold bath soaking and in the hot-cold bath process. process.

It is available in the dry flake form or It is available in the dry flake form or ready to use solution.ready to use solution.

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Concentrated and ready to use Concentrated and ready to use solutions of copper naphthenate are solutions of copper naphthenate are available for mixing with petroleum available for mixing with petroleum oils to make a treating solution that oils to make a treating solution that is effective against termites and is effective against termites and decay.decay.

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Water-borne salts generally do not Water-borne salts generally do not perform as well as preservative oils perform as well as preservative oils under conditions favorable to under conditions favorable to leaching.leaching.

Water-borne salts are principally Water-borne salts are principally used where wood will not be in used where wood will not be in contact with the ground. contact with the ground.

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However, some water-borne salts, However, some water-borne salts, such as those used in the double such as those used in the double diffusion process, have been diffusion process, have been developed to the point where good developed to the point where good performance can be expected even performance can be expected even when the treated wood is in contact when the treated wood is in contact with the ground.with the ground.

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Wood treated with water-borne Wood treated with water-borne preservatives is relatively clean, preservatives is relatively clean, paintable, and free of objectionable paintable, and free of objectionable odor.odor.

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The following are examples of The following are examples of water-borne salts.water-borne salts.• Zinc chloride preservative is relatively Zinc chloride preservative is relatively

inexpensive, has no color, is uniform inexpensive, has no color, is uniform in quality and is not a fire hazard. in quality and is not a fire hazard. It will leach out of wood that is in contact It will leach out of wood that is in contact

with the soil and does not perform as with the soil and does not perform as well as other preservatives.well as other preservatives.

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Chromated zinc chloride and Chromated zinc chloride and copperized chromated zinc chloride copperized chromated zinc chloride were developed as improvements were developed as improvements over zinc chloride. over zinc chloride.

They are more resistant to leaching.They are more resistant to leaching.

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There are a number of commercially There are a number of commercially available patented preservatives available patented preservatives sold under the trade names of the sold under the trade names of the companies that make them. companies that make them. • They are principally used for the They are principally used for the

treatment of wood where there is not treatment of wood where there is not ground contact and where the treated ground contact and where the treated wood will be painted.wood will be painted.

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Odor, paintability, color, and Odor, paintability, color, and combustibility are other factors to combustibility are other factors to consider when choosing a consider when choosing a preservative.preservative.

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Explain the non-pressure preservative Explain the non-pressure preservative treating processes.treating processes.

An alternative to pressure treating An alternative to pressure treating lumber is to use non-pressure lumber is to use non-pressure treating processes.treating processes.

There are several non-pressure There are several non-pressure preservative treating processes.preservative treating processes.

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Superficial application of oil Superficial application of oil preservatives to wood by brushing, preservatives to wood by brushing, spraying, dipping or soaking will spraying, dipping or soaking will increase the service life of the wood increase the service life of the wood by two or three times.by two or three times.

Superficial applications are Superficial applications are recommended only when more recommended only when more effective treatments cannot be used effective treatments cannot be used

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Cold-soaking Cold-soaking involves submerging involves submerging the wood in a preservative solution the wood in a preservative solution for about 48 hours in summer to 72 for about 48 hours in summer to 72 hours in winter.hours in winter.

Wood to be treated with an oil Wood to be treated with an oil preservative should first be dried to preservative should first be dried to a moisture content of 20 to 30 a moisture content of 20 to 30 percent.percent.

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Double-diffusion Double-diffusion is a treatment is a treatment process in which unseasoned wood process in which unseasoned wood is soaked in two separate chemical is soaked in two separate chemical solutions. The two chemicals react solutions. The two chemicals react to produce a preservative that is to produce a preservative that is insoluble in water and is toxic to insoluble in water and is toxic to insects and fungi.insects and fungi.

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Two of the most reasonably priced Two of the most reasonably priced chemicals for use in this treatment chemicals for use in this treatment are technical-grade copper sulfate are technical-grade copper sulfate and technical-grade sodium fluoride and technical-grade sodium fluoride in water.in water.

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Hot-cold bath Hot-cold bath consists of heating consists of heating seasoned wood in a preservative for seasoned wood in a preservative for several hours and then quickly several hours and then quickly submerging the wood in a cold submerging the wood in a cold preservative for several hours more.preservative for several hours more.

Hot-cold bath process uses coal-tar Hot-cold bath process uses coal-tar creosote and other oil preservatives. creosote and other oil preservatives. It is the most effective of all non-It is the most effective of all non-pressure processes.pressure processes.

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Summary / ReviewSummary / Review

1. Explain the principal causes of wood 1. Explain the principal causes of wood deterioration.deterioration.

2. Identify commercial and 2. Identify commercial and noncommercial wood preservatives.noncommercial wood preservatives.

3. Identify naturally durable woods.3. Identify naturally durable woods.4. Describe preservatives used for 4. Describe preservatives used for

wood.wood.5. Explain the non-pressure 5. Explain the non-pressure

preservative treating processes.preservative treating processes.

1 unit d: forest products lesson 4: protecting and preserving wood

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