Seasoning of Wood Informative Summary

Overview:

This book, “Seasoning of Wood,” published in 1917 by Joseph B. Wagner, provides a detailed exploration of the processes involved in preparing lumber for manufacturing. Wagner delves into the complexities of wood structure, highlighting the distinct properties of coniferous and broad-leaved trees. He emphasizes the importance of seasoning wood to enhance its durability, strength, and resistance to decay, as well as reduce shrinkage and warping.

The book meticulously explains the different methods of seasoning wood, ranging from traditional air-drying to more advanced kiln-drying techniques. Wagner scrutinizes the advantages and disadvantages of each method, providing practical advice for selecting the best approach based on the specific type of wood and desired outcome. He also delves into the intricacies of kiln design and operation, highlighting the crucial role of temperature, humidity, and air circulation in achieving optimal drying results.

Key Findings:

Wood is a complex material with distinct properties: Coniferous trees have a simpler structure than broad-leaved trees. This difference significantly impacts the drying process and the resulting properties of the wood.
Seasoning enhances wood’s durability and strength: Removing excess moisture not only prevents warping and cracking but also increases the wood’s resistance to decay and attack by insects.
Kiln-drying offers advantages over air-drying: This method can accelerate the process, reduce losses, and achieve more uniform drying results, although it requires careful control of temperature, humidity, and air circulation.
The correct approach to drying depends on the specific type of wood: Some woods require slow, low-temperature drying while others can withstand higher temperatures.

Learning:

Understanding Wood Structure: The book provides a comprehensive understanding of the internal composition of various wood species, including the role of tracheids, vessels, and medullary rays in determining their properties.
The Significance of Seasoning: Readers gain a thorough appreciation of the benefits of seasoning, including increased durability, resistance to decay, and reduced shrinkage.
Choosing the Right Drying Method: The book equips readers with the knowledge to select the appropriate drying method based on wood type, desired outcome, and available resources.
The Intricacies of Kiln-drying: Readers learn about the critical role of temperature, humidity, and air circulation in kiln-drying, enabling them to understand the principles behind successful operation.

Historical Context:

This book was written during a time of significant industrial growth in the United States. The demand for wood was high, and the need for efficient and effective drying methods was becoming increasingly crucial. The book reflects the growing awareness of the importance of scientific principles in wood processing, as well as the need to optimize resource utilization.

Facts:

Wood substance is heavier than water: This explains why a block of wood sinks in water, even though a hollow, air-filled cell from the same wood would float.
Sapwood dries faster than heartwood: This is due to the presence of free water in the cell cavities of sapwood, while heartwood is only saturated by water within the cell walls.
Different trees contain varying amounts of water: A thrifty tree will hold more water than a stunted one, and a young tree will contain more than an old one.
The width of sapwood varies depending on the species: Some pines, like long-leaf, have narrow sapwood, while others, such as loblolly, have much wider sapwood.
The width of the yearly rings varies with the rate of tree growth: Thrifty trees have wider rings, while slow-growing or stunted trees have narrower rings.
The summer-wood of each ring is denser and darker than the spring-wood: This difference in density and color is largely responsible for the variations in weight and strength of the wood.
The wood of a limb is generally lighter than the wood of the stem: This is because the limb wood contains a greater proportion of spring-wood.
The wood near the base of a limb (knots) is usually heavier than the surrounding wood: This is due to the denser wood fibers that connect the stem and limb.
Color in wood is due to pigments: The different shades of brown in oak, orange brown in pine, and black in walnut are caused by pigments within the wood substance.
Wood becomes more opaque and loses its luster as it decays: This is due to the breakdown of the wood fibers by fungi, rendering the wood less translucent.
Odor in wood is caused by volatile compounds: The scent of pine, cedar, and camphor wood is caused by volatile oils that evaporate from the wood.
Oak is heavier, stronger, and tougher than pine: These differences are largely attributed to the denser structure of oak wood.
The “figure” in oak is caused by its broad, deep medullary rays: These rays are visible on all sections of the wood, adding to its beauty and value.
The “figure” in maple is caused by the boring action of insects: These insects create small pits or grooves that are subsequently filled in by new wood growth.
The “figure” in mahogany is due to the twisted condition of its wood fibers: The unique patterns in mahogany are caused by irregularities in the growth of the fibers, adding to its ornamental value.
The work of different wood-boring insects is distinctive: The galleries and holes created by beetles, borers, and worms vary in size and shape, providing clues to the type of insect responsible.
Ambrosia beetles attack living or dying wood: These beetles require a specific level of moisture in the wood for their fungus to thrive.
Powder post borers attack seasoned wood: They prefer dry, stored material, where they create fine burrows packed with wood dust.
Sapwood decays rapidly when exposed to the weather: The sapwood contains living cells and is more vulnerable to decay than the heartwood.
The heartwood of red gum is quite durable, even in contact with the soil: Although the sapwood of red gum decays quickly, the heartwood is relatively resistant to decay.

Statistics:

49 per cent carbon, 6 per cent hydrogen, 44 per cent oxygen, and 1 per cent ash: This is the approximate dry weight composition of wood for most species.
10 to 15 per cent: This is the typical percentage of bark in a pine tree trunk.
40 to 60 per cent: This is the typical percentage of sapwood in a sound, hard pine log.
10 per cent: This is the typical percentage of summer-wood in the central rings of an old long-leaf pine log.
45 per cent: This is the typical percentage of summer-wood in the stump of an old long-leaf pine log.
24 per cent: This is the typical percentage of summer-wood in the top of an old long-leaf pine log.
16 to 25 per cent: This is the typical percentage of medullary rays in good white oak wood.
30 pounds per cubic foot: This is the approximate dry weight of red gum and tupelo gum wood.
32 pounds per cubic foot: This is the approximate dry weight of tupelo gum wood when dry.
45 to 55 pounds per cubic foot: This is the typical weight range of sapwood in most common lumber woods.
50 pounds per cubic foot: This is the upper limit of weight for most common native woods in the United States.
42 pounds per cubic foot: This is the approximate average weight of hickory, oak, persimmon, osage orange, and black locust when dry.
30 pounds per cubic foot: This is the approximate average weight of southern pine, pitch pine, tamarack, Douglas spruce, and Western hemlock when dry.
24 pounds per cubic foot: This is the approximate average weight of white pine, spruce, and fir when dry.
7 to 10 per cent: This is the typical loss in drying for refractory woods like red gum.
33 per cent: This is the maximum loss in drying for exceptional cases of refractory woods.
60 to 70 per cent: This is the typical loss in air-drying for Western larch.
30 per cent: This is the typical loss in air-drying for red gum.
45 hours: This is the time required to dry 1-inch green red gum from 20.1 per cent to 11.4 per cent moisture.
22 per cent: This is the amount of warping loss observed in the 1-inch green red gum test.

Terms:

Heartwood: The central portion of a tree, made of dead cells that provide structural support.
Sapwood: The outer layer of wood, containing living cells that transport water and nutrients.
Annual rings: The layers of wood that are added to a tree each year, visible on a cross-section.
Springwood: The lighter, softer wood formed in the spring of the year, containing larger pores for water transport.
Summerwood: The darker, denser wood formed in the summer of the year, with smaller pores and thicker cell walls.
Medullary rays: Radial strips of tissue that connect the pith to the bark, transporting nutrients and contributing to the “figure” in certain woods.
Tracheids: Long, narrow cells in coniferous trees, responsible for water transport.
Vessels: Wide, hollow tubes in broad-leaved trees, transporting water and dissolved nutrients.
Hygroscopic moisture: The water absorbed within the cell walls of wood.
Fibre saturation point: The moisture content at which the cell walls of wood become saturated, typically 25 to 30 per cent of the dry wood weight.

Examples:

Redwood: This wood, known for its beautiful reddish color and durability, is used for shingles, water pipes, and interior decorations.
Long-leaf pine: This hard and durable pine is used for heavy construction, shipbuilding, and railway ties.
White oak: This strong and tough oak is used for furniture, tight cooperage, and shipbuilding.
Red gum: This wood, while prone to staining and warping, is increasingly used for furniture, veneers, and boat finishes.
Tupelo gum: This wood, often mistaken for poplar, is highly valued for its strength and workability and is used in slack cooperage, flooring, and boxes.
Hickory: This strong and resilient wood is used for wagon stock, tool handles, and sporting goods.
Black walnut: This valuable wood is prized for its rich color and grain and is used for furniture, gun stocks, and interior finish.
Yellow poplar: This light and durable wood is used for furniture, construction, and woodenware.
Basswood: This soft and easily-worked wood is used for carving, toys, and woodenware.
Maple: This hard and strong wood is used for furniture, flooring, and sporting goods.

Conclusion:

Seasoning is an essential process for maximizing the durability, strength, and stability of wood for manufacturing. While traditional air-drying remains valuable, kiln-drying offers significant advantages in speed, efficiency, and control. Understanding the structure of wood, its properties, and the factors that influence drying are crucial for selecting the most appropriate method and achieving optimal results. By carefully applying the principles outlined in this book, wood processors can achieve optimal seasoning results, reducing losses, improving quality, and enhancing the value of their wood products.

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