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Questions and Answers
What is the main objective of seasoning timber?
What is the main objective of seasoning timber?
Natural seasoning involves quick drying methods to prepare timber.
Natural seasoning involves quick drying methods to prepare timber.
False
What is the height of a single stack of timber during natural seasoning?
What is the height of a single stack of timber during natural seasoning?
3-4 meters
During natural seasoning, timber is stacked in a cross-wise direction under a __________.
During natural seasoning, timber is stacked in a cross-wise direction under a __________.
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Which of the following is NOT an objective of seasoning timber?
Which of the following is NOT an objective of seasoning timber?
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Match the following methods of seasoning timber with their descriptions:
Match the following methods of seasoning timber with their descriptions:
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Natural seasoning is the most prevalent method for drying large structural timber.
Natural seasoning is the most prevalent method for drying large structural timber.
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Name one disadvantage of using water seasoning.
Name one disadvantage of using water seasoning.
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What is the main advantage of kiln seasoning timber?
What is the main advantage of kiln seasoning timber?
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Compartment kilns are designed to season timber progressively as it moves through various air conditions.
Compartment kilns are designed to season timber progressively as it moves through various air conditions.
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What is the typical time required for complete seasoning using Mc.Neill’s Process?
What is the typical time required for complete seasoning using Mc.Neill’s Process?
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Chemicals used for seasoning have lower ______ pressure than pure water.
Chemicals used for seasoning have lower ______ pressure than pure water.
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Match the following kiln seasoning types with their descriptions:
Match the following kiln seasoning types with their descriptions:
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Which of the following methods of seasoning is the most expensive?
Which of the following methods of seasoning is the most expensive?
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Well-seasoned timber can decay easily if left unprotected.
Well-seasoned timber can decay easily if left unprotected.
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What is the purpose of using preservatives on well-seasoned timber?
What is the purpose of using preservatives on well-seasoned timber?
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Which of the following is NOT a type of timber preservative mentioned?
Which of the following is NOT a type of timber preservative mentioned?
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Organic solvent preservatives can be painted after treatment.
Organic solvent preservatives can be painted after treatment.
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What type of preservative must be applied over outside exposed timber?
What type of preservative must be applied over outside exposed timber?
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The process of submerging debarked timber in preservative is called ______.
The process of submerging debarked timber in preservative is called ______.
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Match the preservative type to its characteristic:
Match the preservative type to its characteristic:
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What is an example of a Water Soluble preservative?
What is an example of a Water Soluble preservative?
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The Boucherie Process is a form of water seasoning.
The Boucherie Process is a form of water seasoning.
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What treatment process uses hot and cold baths to sterilize timber?
What treatment process uses hot and cold baths to sterilize timber?
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Study Notes
Timber and Wood-Based Products
- Wood is a hard, fibrous substance forming the trunk and branches of trees.
- Timber is wood retaining its natural structure, suitable for engineering.
- Lumber is roughly sawn and cut wood, ready for use.
Introduction to Trees
- Trees consist of roots, trunk, and crown.
- In autumn, sap descends and forms cambium layers.
- Cambium layers harden to form concentric rings.
- Cambium cells (fibers) are cemented by lignin.
- Arrangement of cells and fibers determines wood grain.
Tree Anatomy
- Annual Rings: Visible rings formed by cambium growth layers.
- Pith: The central core of a tree trunk.
- Heartwood: The central, older, and often darker wood.
- Sapwood: The outer, lighter wood that transports water.
- Cambium: Layer between heartwood and sapwood where new cells are produced.
- Bark: Outer protective layer of the tree.
Tree Grain
- Rapid growth: Wide annual rings result in coarse-grained wood.
- Slow growth: Narrow annual rings lead to fine-grained wood.
- Straight-grained: Wood elements run parallel to the pith.
- Cross-grained: Elements do not run parallel to the pith axis
Timber Classification
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Position based:
- Standing timber: Living tree.
- Rough timber: Part of a felled tree.
- Converted timber: Sawed logs (lumber).
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Elasticity Modulus based:
- Group A: Modulus above 12.5 kN/mm².
- Group B: Modulus above 9.8 kN/mm² & below 12.5 kN/mm².
- Group C: Modulus above 5.6 kN/mm² & below 9.8 kN/mm².
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Seasoning Characteristics:
- Highly refractory (Class A): Slow, difficult to season, no surface defects.
- Moderately refractory (Class B): Seasonable, no surface defects.
- Non-refractory (Class C): Rapid seasoning, no defects.
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Treatability:
- Classifies resistance of heartwood to preservatives.
- Easily treatable
- Treatable but complete preservation is difficult
- Partially treatable
- Very refractory to treatment
- Classifies resistance of heartwood to preservatives.
Characteristics of Good Timber
- Narrow annual rings
- Compact medullary rays
- Dark color
- Uniform texture
- Sweet smell, shining fresh cut surface
- Sonorous sound on impact
- Free from defects
- Heavy weight
- No woolliness at fresh cut surface
Wood Properties
- Physical: Density, specific weight, bulk density, moisture movement, shrinkage, swelling, heat conductivity, sound conductivity, resistance to acids and alkalis.
- Mechanical: Compressive strength, tensile strength, bending strength, stiffness, toughness, cleavability, hardness.
Testing of Timber
- Methods: Specific Gravity, Volume Shrinkage, Radial and Tangential Shrinkage, Static Bending strength, Impact Bending, Compressive Strength, Tensile Strength, Cleavage, Brittleness, Torsional, Moisture Content Tests
Timber Seasoning
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Seasoning: Process to reduce timber moisture content for preventing fermentation and suitability for use.
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Objectives: Reducing shrinkage and warping, increasing strength and durability, reducing tendency for splitting, making suitable for painting, reducing weight.
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Natural/Air Seasoning: Logs stacked in rows in a shed, slow drying rate.
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Artificial Seasoning:
- Water Seasoning: Soaking logs in water to leach out sap, followed by air drying.
- Boiling: Quick, expensive method to remove sap, followed by drying.
- Kiln Seasoning: Large-scale rapid drying in heated chambers using circulating air.
- McNeill's Process: Timber stacked, combusted fuel in the fire place, requires 15-60 days.
- Chemical or Salt Seasoning: Aqueous chemical solutions with lower vapor pressure than pure water.
Timber Preservation
- Preservation: Adds extra protection to seasoned timber using preservatives to prevent decay, water absorption, or attacks from fungi, water, insects etc.
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Methods:
- Surface application: Dipping, spraying, or brushing preservative onto debarked timber.
- Soaking treatment: Submerging debarked timber in preservative solution.
- Hot and Cold Process: Two baths (hot water and preservative) are used for sterilization against insects and fungi.
- Boucherie process: Logs attached via hose pipes to a reservoir with preservatives to replace sap through hydrostatic pressure.
Defects in Timber
- Defects often occur during the growing, conversion or seasoning process.
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Abnormal Growth Defects:
- Checks: Longitudinal cracks perpendicular to the rings.
- Shakes: Longitudinal separations between annual rings. (e.g., heart shake, cup shake, star shake)
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Other Defects:
- Rind gall: Swelling caused by sap over wounds.
- Knots: Bases of twigs or branches embedded in the stem.
- End splits: Splits at the ends of logs.
- Twisted fibres: Fibres twisted by constant wind during growth.
- Upsets: Crushing of fibers during growth or felling.
- Foxiness: Yellow or red discoloration due to decay.
- Rupture: Damage caused by injury or impact.
- Defects from conversion practice: Defects due to poor milling or attempts to economize.
- Defects from seasoning: Errors in moisture content from uneven or inadequate drying.
- Common seasoning defects: Checks, splittings, warpage (e.g., cupping, twisting, bowing)
Decay in Timber
- Timbers are affected by fungi, insects, rodents, weather, and chemicals.
- Sapwood is more vulnerable to decay than heartwood.
- Fungal/Bacterial attack: Fungi produce spores that create mycelia that destroy wood tissue. Require moisture.
- Insect attack: Varying levels and types of insects can affect timber.
- Rodent damage: Rodents can penetrate both wood and concrete.
Wood Products
- Wood-based products are developed to use timber efficiently.
- Manufactured under controlled conditions, with desired shapes, dimensions, strength, and durability.
- Raw materials come from timber waste or unused tree parts.
- Gluing material influences product durability
Veneer (IS 14315)
- Primary process in manufacturing wood-based products.
- Veneer thickness ranges from 0.4mm - 0.6mm.
- Logs stored in cold storage to avoid splitting
- Barks removed and cut into veneers
- Two types: Rotary and Sliced veneer
- Defectives based on surface quality (A and B grades) based on discoloration, dotes, etc.
Plywood (general)
- Layers of veneer glued together in odd numbers (3,5,7).
- Improves dimensional stability. , stiffness and strength
- Outer layers are known as faces
- Interior layers are known as the cores.
- Plywood categories are based on appearance, bond strength, moisture resistance
Plywood Manufacturing Process
- Veneers are dried to specific moisture content,
- Cooled, to regulate air temp,
- Veneers with moisture issues will be redried,
- Veneer edges may be glued to create larger sheets (composing process).
- Veneers may undergo a finishing process with edges trimmed, and surfaces sanded.
Plywood Merits
- Good strength and stability.
- Reduces shrinkage and swelling.
- Better resistance to splitting.
- Superior strength-to-weight ratio to many materials
Block Boards (IS 1659)
- Solid core plywood boards made from wood strips or slabs.
- Veneers glued between wood pieces.
- Veneers can be rotary or sliced.
- Thickness of cross-bands range from 1 - 3mm.
- Different grades based on construction and intended use (interior or exterior applications).
Particle Boards (IS 3129, 12406, 3478)
- Made from wood chips, or other cellulose materials,
- Materials pressed together, using organic binder.
- Created from wood waste.
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Description
Test your knowledge on the objectives and methods of timber seasoning. This quiz covers natural and kiln seasoning, their pros and cons, and specific terminology related to timber drying. Perfect for students in forestry or environmental science courses.
