Chemical Seasoning of Timber: Quiz and Flashcards

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Questions and Answers

What is the outermost layer or skin of the trunk of an exogenous tree?

Bark or cortex

What is the innermost part or core of the tree in an exogenous tree?

Pith, heart or medulla

What is the layer of fibro-vascular bundle of the first year surrounding the pith in an exogenous tree?

Medullary sheath

What consists of the inner annual rings round the pith in an exogenous tree?

Heartwood or duramen Signup and view all the answers

What are composed of a series of hard flattened cells lying one above another, vertically in rows, in an exogenous tree?

Medullary rays or transverse septa Signup and view all the answers

In what type of trees can fibrous mass be seen in the longitudinal sections?

Endogenous trees Signup and view all the answers

What are the requirements of good timber?

Uniform color, regular annual rings, bright appearance, silky luster, clear sound, well seasoned, free from defects, hard, durable, tough, not affected by wood rotting, and sweet-smelling when fresh. Signup and view all the answers

When is the best time for cutting a timber tree?

Immediately after it has attained full growth or during mid-summer when the sap quantity is minimum and at rest. Signup and view all the answers

What is wood seasoning?

The process of removal of sap from timber. Signup and view all the answers

Why is seasoned wood preferred?

To render timber easy to work with, increase its strength, and make it less liable to warp, shrink, crack, twist, and split. Signup and view all the answers

How do you prepare timber for seasoning and why?

Timber needs to be cut to allow air access into the pores, hasten drying, facilitate uniform shrinkage, and ensure even drying throughout the timber. Signup and view all the answers

What are some tree species with limited engineering applications?

Bamboo, Cane, Palm, and Coconut tree. Signup and view all the answers

What is rot and decay in wood?

Rot is the disintegration of wood fiber caused by microscopic organisms like mold and fungus. Signup and view all the answers

Which woods are naturally resistant to rot?

Woods like cedar and redwood contain natural 'extractives' that make them resistant to rot. Signup and view all the answers

What are the conditions required for fungi to thrive and cause decay in wood?

Fungi require oxygen, temperatures of 40° to 100°F, moisture (30% or more), and a food source (wood) to thrive. Signup and view all the answers

How can one prevent decay on a deck?

The best way to avoid decay is to keep the deck dry before and after installation. Signup and view all the answers

What is the significance of applying a topical chemical treatment to the edge or ends of a pressure-treated board used in deck construction?

It helps prevent decay by protecting the vulnerable areas from rot and fungi. Signup and view all the answers

How do wood-boring insects like beetles, moths, and wasps contribute to wood damage?

They feed on wood and make their home there, especially in wood that exceeds 30% moisture content. Signup and view all the answers

What is the purpose of charring charred wood?

To weatherproof the siding and act as a deterrent to insects. Signup and view all the answers

How deep is the wood charred in the process of charring charred wood?

6 mm to 12 mm deep. Signup and view all the answers

What is the creosoting method used for in timber preservation?

To protect timber from white ants, rot, and increase its lifespan. Signup and view all the answers

What is the pressure at which creosote is forced into timber in the creosoting method?

10 kg/cm2 at 48 oC. Signup and view all the answers

What is the purpose of varnishing or French polishing timber?

To provide a transparent surface coating that changes to a hard solid. Signup and view all the answers

What are the components of varnish or French polish?

Resins, solvents, and driers. Signup and view all the answers

What is chemical seasoning also known as?

salt seasoning Signup and view all the answers

What is the purpose of chemical seasoning?

to slow down the rate at which moisture is lost Signup and view all the answers

How is uniform seasoning ensured across the cross-section of timber using chemical seasoning?

as a preliminary treatment Signup and view all the answers

What is the purpose of using salts like sodium chloride or sodium nitrate in chemical seasoning?

to draw out the inner moisture of timber Signup and view all the answers

What is the role of a kiln supervising tool?

to keep a check on kiln conditions and determine kiln-drying schedules Signup and view all the answers

How does the reconditioning chamber help in the kiln seasoning process?

determines damage to cells of timber near-surface and refills moisture back into outer cells Signup and view all the answers

Study Notes

Characteristics of Exogenous Trees

Hard wood, dark in color, hard, close-grained, and strong
Useful for important engineering works

Structure of an Exogenous Tree

Bark or cortex: outermost layer or skin of the trunk, covering the wood
Cambium: thin layer of thickened sap just beneath the bark
Sapwood: light in weight, broad annual rings, and liable to decay (not yet matured wood)
Annual ring: consists of innumerable closed cells of woody fibers and tissues arranged in a distinct concentric ring or circle around the pith
Pith, heart, or medulla: innermost part or core of the tree, represents the first formed central portion of the stem, consisting entirely of cellular tissues
Medullary sheath: layer of fibro-vascular bundle of the first year surrounding the pith
Heartwood or duramen: consists of the inner annual rings around the pith, dark in color, hard, strong, compact, and durable
Medullary rays or transverse septa: composed of a series of hard, flattened cells lying one above another, vertically in rows, binding the annual rings together

Characteristics of Endogenous Trees

Grow inwards, with a fibrous mass visible in longitudinal sections
Limited engineering applications
Examples: Bamboo, Cane, Palm, and Coconut trees

Requirements of Good Timber

Uniform color and regular annual rings
Bright appearance and silky luster
Clear sound when struck
Well-seasoned
Free from natural defects
Not affected by wood rotting, fungi, etc.
Hard, durable, and tough
Does not split when a nail is driven into it
Sweet smell when freshly cut

Best Time for Cutting a Timber Tree

Immediately after it has attained full growth to obtain maximum quantity of wood at its most endurable state
During mid-summer when the quantity of sap is minimum and at rest

Wood Seasoning

Process of removing sap from timber
Rendering timber easy to work with
Increasing its strength
Making it less liable to warp, shrink, crack, twist, and split

Preparation of Timber for Seasoning

Cutting timber to give free access of air into the pores of green timber
Facilitating uniform shrinkage and drying throughout the timber