wood basics

Wood Basics

Understanding the characteristics of wood.

The Make Up of WoodWood can be defined as the whole of several distinct attributes found in the growth of a tree.• Bark, Cambium, Bast, Sapwood, Heartwood and the Pith

Wood GrainWhen we look at wood grain, we see a cross section of the growth rings and medullary rays in relation to how the tree is sawn.

The Cut Makes the Difference

Grain AnomaliesWavy and irregular grain patterns in combination with proper finish and light reflectivity, can make for highly desirable wood. This effect is most commonly referred to as “figure”.

Wood BurlsA wood burl is a type of “figure” resulting from a deformity in the tree. It can form as a result of disease, injury or natural mutation.

Kiln DryingMost furniture grade wood is sawn, carefully stacked and slowly dried in a controlled manner in a kiln.

StickeringThe wood is carefully stacked according to thickness and width. It is evenly spaced for airflow and weighted to retain flatness.

When Things Go Wrong

End Grain Checking Lumber Checking

TensionMost lumber retains some tension during the drying process and it can be seen in a number of ways…

Movement

Directional Movement Seasonal Effect

Different Cuts Move Differently

Every piece of the log has its own movement characteristics

Movement in Fabrication

Careful selection is important when considering movement in fabricated work.

Expansion and Contraction Remedies

Expansion and contraction can be dealt with in a variety of ways when constructing furniture built from solid wood.

• Proper drying techniques.• Careful arrangement of grain.• Proper Milling.• Selecting the right joinery.• Using veneers or plywood when necessary. (Some people call

this cheating but everything has its place.)

What is a veneer?

Rotary Cut Quarter Sawn or Plain Sliced

Plywood

Plywood is used as a super stable product with terrific sheer strength end to end. These qualities are derived from how it is constructed.

The Janka Scale

The hardness of wood is measured on a relative scale based on the resistance of a sample of wood to denting.

A Quick Glimpse of the Scale

Measured in lbs of force.• Balsa 100• Basswood 410• Douglas Fir 660• African Mahogany 830• Cherry 995• Walnut 1010• White Oak 1360• Rosewood 1780• Australian Buloke 5060