2.3: Grain, Figure, and Wood Movement

2.3 Grain, Figure, and Wood Movement

Learning to read a board is one of the most important skills you will develop as a woodworker.

Grain direction affects machining. Figure affects appearance. Growth-ring orientation influences how a board looks and how it may respond to changes in moisture.

Learning Outcomes

After completing this section, you should be able to:

• Distinguish between grain, texture, and figure.
• Explain why moisture content matters.
• Describe basic methods of drying lumber.
• Identify plainsawn, riftsawn, and quartersawn lumber.
• Explain how growth-ring orientation affects the appearance and behavior of a board.

Grain

Grain describes the arrangement and direction of the wood fibers and growth structure.

Grain direction matters whenever a cutting edge meets the wood.

Cutting with favorable grain generally produces a cleaner surface. Cutting against unfavorable grain can cause fibers to lift and break ahead of the cutter, producing tearout.

Later in this course, you will learn to read grain direction before using machines such as the jointer and planer.

Figure

Figure is the visible pattern seen on the face or edge of a board.

Figure may result from:

• the orientation of the growth rings;
• anatomical structures such as rays;
• changes in grain direction;
• color variations; or
• unusual growth within the tree.

Figure is one of the reasons wood is such a visually expressive material.

Two boards from the same species can have completely different figure, and choosing how that figure appears in a finished piece is an important part of woodworking and furniture making.

Texture

Texture describes the relative size and uniformity of the wood's cellular structure.

A fine-textured wood has relatively small, closely spaced cells. Other woods have larger, more open structures.

Texture can influence the appearance of the surface and how the wood sands and finishes.

Moisture Content

Wood contains water.

Moisture content is the weight of the water in the wood compared with the oven-dry weight of the wood, expressed as a percentage.

As wood gains and loses moisture, its dimensions can change.

This is referred to generally as wood movement.

Wood movement is important because a project may be built under one set of environmental conditions and later live in another. A woodworker must allow for this movement rather than assuming that wood will remain permanently unchanged.

Understanding wood movement becomes increasingly important as projects become larger and more complex.

Drying Lumber

Freshly cut wood contains too much moisture for most furniture and cabinet work and must be dried.

There are two basic methods.

Kiln Drying — Lumber is dried in a controlled environment using circulated heated air. Most hardwood used for typical furniture woodworking is kiln dried.

Air Drying — Lumber is stacked so ambient air can circulate around all surfaces.

Small strips called stickers are placed between layers of lumber to create air space.

A traditional rule of thumb is approximately one year of air drying per inch of thickness, although actual drying time depends on species, climate, thickness, airflow, and other conditions.

How a Log Is Sawn

The orientation of a board within the log affects both its grain pattern and its physical behavior.

Three common terms are:

Plainsawn or Flatsawn

The board is cut roughly tangent to the growth rings, with the rings generally intersecting the face at less than about 45 degrees.

Plainsawing:

• produces wide boards;
• creates relatively little waste;
• is economical; and
• often produces the familiar cathedral-shaped grain pattern.

Riftsawn

The growth rings meet the face of the board at approximately 45 degrees.

Riftsawn lumber commonly produces a straighter, more consistent grain pattern on both the face and edge.

Quartersawn

The growth rings are oriented more nearly perpendicular to the face of the board.

Quartersawn lumber:

• generally produces straight grain;
• is more dimensionally stable;
• can highlight ray structure; and
• can create distinctive figure in species with prominent rays.

Diagram comparing plainsawn, riftsawn, and quartersawn boards according to the angle of the growth rings to the board face and showing the resulting grain patterns.

Figure: Methods of Cutting Lumber

Growth Rings and Movement

Wood does not shrink and swell equally in every direction.

The orientation of the growth rings within a board affects how that board tends to change shape as its moisture content changes.

This is one reason two boards cut from different locations in the same log may behave differently.

You will see this again when evaluating cup, bow, crook, and twist and when deciding how to orient boards within a project.

Check Yourself

1. What is the difference between grain and figure?
2. Why does grain direction matter when machining wood?
3. What is moisture content?
4. What are stickers used for when drying lumber?
5. How do plainsawn, riftsawn, and quartersawn lumber differ?
6. Which sawing orientation tends to highlight ray structure?