SYLLABUS
INTRODUCTION
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Sometimes when I am looking through my 'lumber library' I come across a piece of wood that seems to know exactly what it wants to become. Then, it's just a matter of listening to the wood and carefully revealing the object hidden inside as it tells you to.
That's the best-case scenario for starting a new project, in my opinion.
However, 99% of the time I'll have an idea about what I want to make (and, on very rare occasions, I might even have an actual PLAN) so the next logical step in the process is to determine which materials I'll use to make the 'thingy' out of.
There are a bunch of things to consider when choosing what wood species to use in a project:
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Is the final product intended for indoor or outdoor use?
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What is the budget for materials used in the project?
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Does the final product need to bear weight? Is strength and density of the wood a factor?
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Does the design have intricate details or specific color requirements?
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Are you able to source enough of that wood to complete the project?
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Does the product need to be safe for contact with food?
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If the product is crafted from wood that is known to cause sensitivity, is that an issue?
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Is the wood you are considering using for your project dry enough?
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Does the final product need to be lightweight?
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And on, and on, and on, ad infinitum...
If this seems to you like an overwhelming amount of factors to have to take into account, you are correct!
However, armed with a little bit of understanding about the materials you are working with, you'll soon be able to choose the appropriate wood species for your design like a pro woodworker.
THE ANATOMY OF WOOD
The anatomy of wood is a fascinating subject that delves into the intricate structure of one of nature's most versatile materials. Understanding wood anatomy is essential for anyone interested in woodworking, forestry, or simply appreciating the natural world.
At its core, wood is a complex, fibrous tissue found in the stems and roots of trees and other woody plants. Its primary function is to support the plant, conduct water and nutrients, and store various biochemical compounds. To fully grasp wood anatomy, it's helpful to explore its three main structural components: the outer bark, the cambium layer, and the inner wood, which includes the sapwood and heartwood.
The outer bark is the protective outermost layer of the tree. It serves as a shield against physical damage, pests, and diseases. Beneath the outer bark lies the cambium layer, a thin but crucial part of the tree. The cambium is responsible for the growth of new cells, allowing the tree to increase in girth over time. It produces the inner wood (xylem) on the inside and the outer bark (phloem) on the outside. The inner wood is divided into two distinct zones: the sapwood and the heartwood. Sapwood is the younger, outermost part of the wood that is still active in transporting water and nutrients from the roots to the leaves. It is usually lighter in color and more susceptible to decay. Heartwood, on the other hand, is the older, central part of the wood. It no longer participates in nutrient transport but provides structural strength to the tree. Heartwood is typically darker and denser due to the accumulation of resins, tannins, and other substances that make it more resistant to decay and pests.
Wood is primarily composed of cellulose, hemicellulose, and lignin. Cellulose fibers provide strength and rigidity, while hemicellulose acts as a matrix that holds the cellulose fibers together. Lignin is a complex organic polymer that fills the spaces between cellulose fibers, adding to the wood's overall hardness and resistance to decay.
The cellular structure of wood also plays a vital role in its properties. Wood cells, or tracheids, are elongated and arranged in a parallel fashion, contributing to the wood's grain. This grain pattern influences the wood's appearance and its mechanical properties. The orientation and size of these cells vary between different types of wood, resulting in the wide variety of wood species, each with its unique characteristics.
Think of wood as a stack of straws (tracheids) held together by glue (lignin).
Examining the anatomy of wood reveals the complex and layered structure that makes it such a valuable material. From the protective outer bark to the supportive heartwood, each component plays a crucial role in the tree's growth, strength, and resilience. Understanding these elements provides a deeper appreciation for wood's versatility and its importance in both natural ecosystems and human industries.
GRAIN DIRECTION AND DENSITY
The direction and density of wood grain are critical factors that significantly impact the performance, appearance, and overall quality of wooden products. Whether you are crafting furniture, constructing buildings, or creating art, understanding how these aspects influence the properties of wood can enhance your work and ensure the durability and beauty of your creations.
Wood grain refers to the alignment, texture, and pattern of the wood fibers. Grain direction is determined by the way these fibers grow along the length of the tree. This direction can be straight, spiral, interlocked, or wavy, each imparting distinct characteristics to the wood. Straight-grained wood, where the fibers run parallel to the length of the board, is typically easier to work with, offering predictable strength and stability. Spiral or interlocked grains, on the other hand, can present challenges during cutting and shaping but often result in visually striking patterns.
Spiral Grain
Larch
Interlocking Grain
Sapele
Wavy Grain
Claro Walnut
Straight Grain
Red Cedar
The direction of the grain affects several key properties of wooden products. For instance, wood is generally stronger and more resistant to splitting along the grain. When subjected to bending or tensile forces, straight-grained wood can better withstand the stress, making it ideal for load-bearing structures like beams and joists. Conversely, wood with an irregular grain direction may have enhanced aesthetic appeal but might require more careful handling to prevent warping or breakage during processing.
Wood density, measured as the mass per unit volume, also plays a crucial role in determining the material's suitability for different applications. High-density woods, such as oak and mahogany, are heavier, harder, and more durable. These woods are preferred for high-traffic areas, furniture that must bear significant weight, and decorative elements that benefit from their rich texture and strength. Low-density woods, like pine and cedar, are lighter and softer, making them easier to cut, shape, and join. These woods are often used for applications where ease of handling and quick construction are essential, such as in framing, paneling, and certain types of cabinetry.
The combination of grain direction and density influences the wood's response to environmental factors. High-density, straight-grained woods are less prone to expansion and contraction due to moisture changes, making them more stable in varying climates. This stability is particularly important for outdoor structures and items that must maintain their shape and integrity over time. On the other hand, woods with complex grain patterns or lower density may require additional treatments, such as sealing or reinforcement, to enhance their durability and resilience.
In summary, the direction and density of wood grain are fundamental characteristics that determine the behavior and suitability of wood for various applications. Understanding these factors allows craftsmen, builders, and designers to select the right type of wood for their projects, ensuring that the final products are not only functional and durable but also aesthetically pleasing. By appreciating the nuances of wood grain direction and density, one can better harness the natural beauty and strength of this versatile material.
THE JANKA HARDNESS SCALE
Developed by American researcher Gabriel Janka, the Janka Hardness Test measures a wood sample's resistance to wear and denting. Specifically, it determines how much force is needed to embed a small steel ball halfway into the wood. This test provides a numerical value, which indicates the wood's hardness.
Knowing the hardness of wood is crucial for several reasons. Firstly, harder woods are more resistant to dents and scratches, making them ideal for high-traffic areas or heavy-use furniture. Secondly, softer woods are easier to cut and shape, which can be beneficial for certain projects. Lastly, the test helps in selecting the right wood for specific applications, whether it’s flooring, furniture, or construction.
The test is conducted by preparing a small, standardized sample of the wood. A steel ball with a diameter of 0.444 inches (11.28 mm) is then pressed into the wood. The amount of force required to press the ball halfway into the wood (to a depth equal to the radius of the ball) is recorded. This force is measured in pounds-force (lbf) or newtons (N).
The results are easy to interpret. A high Janka rating indicates a harder wood. For example, Brazilian walnut (Ipe) has a very high Janka rating of around 3,680 lbf, making it extremely hard and durable. Conversely, a low Janka rating indicates a softer wood. For example, balsa wood has a very low Janka rating of about 100 lbf, making it very soft and easy to work with.
The Janka wood hardness test has practical applications in various fields. In flooring, hardwoods like oak and maple are popular due to their high Janka ratings. For furniture, different hardness levels are preferred depending on the type of furniture. Dining tables might use harder woods, while decorative pieces might use softer varieties.
In summary, the Janka wood hardness test is a straightforward method to gauge the hardness and durability of different types of wood. It helps you choose the best wood for your needs based on how well it can withstand dents and wear. You can see where your favorite woods lie on the Janka Hardness Scale below (click [show more] to see the full chart).
MOISTURE CONTENT AND WOOD MOVEMENT
Wood moisture content plays a pivotal role in determining how wood expands and contracts, directly influencing the stability and longevity of wooden furniture. Understanding the effects of wood moisture content and subsequent wood movement is essential for anyone involved in woodworking or furniture making, as it can significantly impact the final product's performance and durability.
Moisture content in wood refers to the amount of water contained within its fibers, typically expressed as a percentage of the wood's dry weight. Wood is hygroscopic, meaning it absorbs or releases moisture depending on the surrounding environment's humidity levels. When wood absorbs moisture from the air, it swells; when it loses moisture, it shrinks. This process of expansion and contraction, known as wood movement, is a natural response to changes in relative humidity and temperature.
The degree of wood movement is influenced by the wood species, grain orientation, and initial moisture content. Generally, wood expands and contracts more across the grain than along its length. For instance, quarter-sawn boards, where the grain runs perpendicular to the board's surface, exhibit less movement compared to plain-sawn boards, which have a more parallel grain direction.
Wood movement can have several effects on furniture. If furniture is crafted from wood that is not adequately dried or acclimated to its environment, it is likely to undergo significant changes as it adjusts to the ambient conditions. This can lead to various issues, including warping, cupping, and splitting. Warping occurs when different parts of a wood piece expand or contract unevenly, causing the wood to twist or bend. Cupping is a specific form of warping where the edges of a board rise or sink relative to the center, creating a concave or convex shape. Splitting happens when the stress from wood movement exceeds the wood's strength, causing cracks to form.
bow
crook
kink
cup
twist
These effects can compromise the structural integrity and aesthetic appeal of furniture. For example, a wooden tabletop that cups or warps may become uneven, affecting its functionality and visual appeal. Similarly, doors and drawers may become misaligned or difficult to open and close if the wood expands or contracts significantly.
To mitigate the adverse effects of wood movement, woodworkers and furniture makers employ several strategies. One crucial step is ensuring that wood is properly dried to an appropriate moisture content before use. Kiln drying or air drying can help achieve this, reducing the likelihood of significant movement once the wood is incorporated into furniture. Additionally, allowing the wood to acclimate to the environment where the furniture will be used can further stabilize its moisture content.
Design considerations also play a vital role in managing wood movement. Allowing for expansion and contraction in the construction of furniture joints can help accommodate natural wood movement. Techniques such as using floating panels in doors and tabletops, and incorporating mechanical fasteners or joinery that permits slight movement, can enhance the durability and stability of the finished piece.
In summary, wood moisture content and its effects on expansion and contraction are critical factors in woodworking and furniture making. Properly managing wood movement through careful drying, acclimation, and thoughtful design can ensure that wooden furniture remains stable, functional, and beautiful over time. Understanding these principles allows craftsmen to create pieces that withstand the test of time, maintaining their integrity and appeal in varying environmental conditions.
WHY USE KILN-DRIED WOOD?
Kiln-dried wood is highly valued in furniture construction for its numerous advantages. This process involves drying wood in kilns where temperature, humidity, and air circulation are controlled, reducing the wood's moisture content to an ideal level, typically around 6-8% for indoor furniture.
The primary benefit of kiln-dried wood is its stability. Lower moisture content means the wood is less likely to warp, twist, or crack with changes in humidity and temperature, ensuring that furniture retains its shape and integrity over time.
Durability is another major advantage. Kiln drying eliminates moisture that can cause decay and attract insects, making the wood more resistant to these threats and extending the lifespan of the furniture.
Kiln-dried wood is also easier to work with. Its uniform moisture content reduces internal stresses, making it more predictable and manageable during cutting, shaping, and joining. This allows for more precise craftsmanship and results in a smoother, more polished finish.
Moreover, kiln-dried wood is consistent and readily available. The controlled drying process ensures that each batch meets specific quality standards, providing a reliable material for both small-scale artisans and large-scale manufacturers.
In summary, the benefits of using kiln-dried wood in furniture construction include increased stability, enhanced durability, improved workability, and consistent quality. These advantages make kiln-dried wood an excellent choice for creating durable, attractive, and long-lasting furniture.
REGARDING WOOD SENSITIVITY
When purchasing wooden furniture, it's important for customers to understand wood sensitivity and toxicity. These factors can affect both the safety and comfort of using wooden products in your home.
Wood sensitivity refers to how certain types of wood can cause allergic reactions or skin irritations. Some people may develop contact dermatitis or respiratory issues when exposed to specific woods. Common allergenic woods include cedar, mahogany, and oak. For those with sensitivities, it is essential to choose furniture made from hypoallergenic woods or ensure that the wood is properly sealed and finished to minimize direct contact with irritants.
Toxicity in wood is another critical consideration. Certain wood species contain natural toxins that can be harmful if ingested or inhaled, particularly when the wood is being cut or sanded. For example, yew and oleander are known for their toxic properties. While the risk is lower in finished furniture, it's still important to be aware of potential hazards, especially if you have pets or small children who might chew on furniture.
Furthermore, the finishes and treatments used on wooden furniture can also introduce toxic substances. Some varnishes, stains, and sealants contain volatile organic compounds (VOCs) that can off-gas and affect indoor air quality. To ensure a healthier home environment, look for furniture finished with low-VOC or non-toxic products. Certifications like GREENGUARD or Oeko-Tex can help identify items that meet stringent safety standards for chemical emissions.
Another aspect to consider is the source and treatment of the wood. Reclaimed wood, while environmentally friendly, might have been treated with chemicals or exposed to pollutants over its lifetime. Ensure that any reclaimed wood furniture has been properly cleaned and treated to remove any hazardous substances.
For customers concerned about wood sensitivity and toxicity, it’s advisable to ask manufacturers or retailers about the types of wood used, any potential allergens, and the finishes applied. Additionally, performing a patch test on a small area of skin can help identify any allergic reactions before fully committing to a piece of furniture.
In summary, understanding wood sensitivity and toxicity is crucial for making informed decisions when buying wooden furniture. Be aware of potential allergens and toxins, choose hypoallergenic woods or properly finished pieces, and opt for low-VOC or non-toxic finishes to ensure a safe and comfortable home environment. By considering these factors, you can enjoy the beauty and functionality of wooden furniture without compromising on health and safety.
CHOOSING WOOD FOR OUTDOOR USE
When choosing wood species for outdoor furniture, it's essential to consider factors like durability, resistance to weather, and ability to withstand pests.
Teak is highly recommended due to its exceptional durability and natural resistance to moisture, insects, and decay. Its natural oils provide excellent protection against the elements, and it develops a desirable silver-gray patina over time.
Cedar is another excellent choice, valued for its natural resistance to rot, insects, and decay. Lightweight and easy to work with, cedar weathers to a grayish color if left untreated but can also be stained or sealed to maintain its original look.
Redwood is praised for its durability and natural resistance to insects and decay. It has a rich color and maintains stability well, reducing the likelihood of warping or splitting. This makes it a suitable option for outdoor furniture.
Ipe is an exceptionally dense and hard wood, making it highly resistant to moisture, insects, and rot. Known for its beautiful dark brown color, Ipe is highly durable and can withstand harsh conditions. Its density also helps it resist scratches and dents.
Mahogany, while often used for upscale outdoor furniture, offers good resistance to moisture and insects. It features a rich color and straight grain, though it may require regular maintenance to preserve its finish.
Acacia is a robust and relatively affordable hardwood that performs well outdoors. It naturally resists moisture and insects and has a beautiful grain that can be enhanced with staining or sealing. Acacia's density, hardness, and durability make it the perfect choice for heavy-use outdoor pieces.
Eucalyptus is a sustainable option with natural resistance to decay and insects. It performs well outdoors and offers a durable and attractive appearance, though it typically requires periodic sealing to maintain its color and durability.
White oak is another durable hardwood known for its toughness and resistance to moisture and insects. Properly treated, white oak can be a good choice for outdoor furniture, offering both durability and aesthetic appeal.
When selecting wood for outdoor furniture, consider its natural oils and preservatives, the level of maintenance required, and the environmental impact of sourcing. Balancing these factors will help ensure that the furniture performs well and maintains its appearance over time.
SOFTWOOD VS. HARDWOOD
Softwood and hardwood are two primary categories of wood, each with distinct characteristics that influence their suitability for various products. Understanding these differences can help you make informed choices about the type of wood best suited for your needs.
Softwood comes from coniferous trees, such as pine, cedar, and spruce, which typically have needle-like leaves and produce cones. These trees grow faster and are often found in temperate and boreal forests. Softwood is generally lighter in weight and softer compared to hardwood. Its grain is usually more uniform and straight, which makes it easier to cut and shape. Softwoods are often used in construction, furniture, and cabinetry, where they offer a good balance of workability and cost-efficiency. For instance, pine is popular for furniture and framing due to its affordability and ease of handling. However, because softwoods are more prone to dents and scratches, they may require additional finishing or protection to enhance durability.
Hardwood, on the other hand, comes from deciduous trees, such as oak, maple, and walnut, which shed their leaves annually. These trees generally grow more slowly and are found in temperate and tropical forests. Hardwoods are typically denser and heavier than softwoods, with a more varied and often more complex grain pattern. This density contributes to hardwoods' greater durability and strength, making them ideal for high-quality furniture, flooring, and cabinetry. For example, oak's durability and attractive grain make it a popular choice for furniture that needs to withstand heavy use. The intricate grain patterns of hardwoods also lend themselves well to detailed carving and high-end finishes.
The differences in density and grain between softwood and hardwood affect their performance in various applications. Softwoods, being lighter and easier to work with, are often chosen for products that require straightforward processing and cost-effectiveness. However, they may not hold up as well under heavy use without proper treatment. Hardwoods, with their superior strength and durability, are preferred for applications where longevity and aesthetic appeal are paramount. Their denser composition makes them more resistant to wear and tear, but this can also make them more challenging to work with and more expensive.
In summary, the primary difference between softwood and hardwood lies in their origin, density, and grain characteristics. Softwoods are lighter, more affordable, and easier to work with, making them suitable for a wide range of applications where cost and ease of handling are important. Hardwoods are denser, more durable, and often more visually appealing, making them ideal for high-quality, long-lasting products. Understanding these differences can help you choose the right type of wood for your specific needs and ensure the best results for your projects.
ALL ABOUT PLYWOOD
Plywood is a versatile and widely used engineered wood product composed of thin layers, or "plies," of wood veneer that are bonded together with adhesive. The manufacturing process begins with logs that are debarked and cut into large sections called "billets." These billets are then peeled into thin veneer sheets, typically about 1/16 to 1/8 inch thick, using a lathe or cutting machine.
After peeling, the veneer sheets are dried to remove excess moisture, which helps prevent warping and ensures proper bonding. Once dried, the veneers are coated with adhesive. Different adhesives are used depending on the plywood’s intended application; for example, phenolic resin is used for exterior-grade plywood, while urea-formaldehyde is used for interior applications.
The coated veneer sheets are then stacked in a specific pattern, with each layer oriented perpendicular to the one below it. This cross-grain layering is crucial for the plywood’s strength and stability. The stacked veneers are pressed under heat and pressure in a hydraulic press, which cures the adhesive and bonds the layers together into a cohesive panel.
After pressing, the plywood panels are trimmed to size, sanded to achieve a smooth finish, and inspected for quality. Additional treatments or coatings may be applied based on the plywood's intended use.
Plywood offers several advantages, including strength and stability due to its cross-grain construction, which distributes loads evenly and reduces the risk of warping or cracking. Its versatility allows it to be manufactured in various thicknesses, sizes, and grades, making it suitable for a wide range of construction and furniture applications. Compared to solid wood, plywood is often more affordable and efficient, utilizing wood fibers effectively and allowing the use of different wood species.
Furthermore, plywood provides uniform quality and appearance, avoiding the natural defects such as knots and irregular grains found in solid wood. Its dimensional stability ensures that it remains consistent in size despite changes in moisture or temperature. Additionally, plywood is eco-friendly, as it makes efficient use of wood resources by utilizing thin layers of veneer and minimizing waste. Overall, its strength, versatility, and cost-effectiveness make plywood a popular choice in both construction and furniture manufacturing.
THE AMAZING WORLD OF VENEER
Veneer is a thin slice of wood, typically less than 3 millimeters thick, that is applied to core panels like wood, particle board, or medium-density fiberboard (MDF) to create flat surfaces such as doors, tops, and cabinet panels. It is also used for decorative purposes, providing an attractive wood finish to various products.
The production of veneer starts with logs that are debarked and trimmed to remove any defects. These logs are then cut into sections known as billets, which are placed in a lathe to peel off thin layers of wood. Alternatively, a saw may be used to slice the wood into veneer sheets. The resulting veneer sheets are dried to eliminate excess moisture, which helps prevent warping and cracking. After drying, the veneers are sorted and classified based on their grain patterns, color, and quality. They are then glued onto core materials such as plywood or MDF to form a panel with a wood veneer surface.
Veneer is widely used for its aesthetic appeal, as it provides a beautiful and high-quality wood finish that enhances the look of furniture and cabinetry. It allows manufacturers to achieve the appearance of expensive solid wood at a more affordable cost by applying a thin layer of veneer to a less costly core material, thereby reducing production costs while still delivering a premium finish.
In addition, veneer contributes to stability and consistency. When applied to core panels like plywood or MDF, it helps minimize issues such as warping, cracking, or splitting, which are more common with solid wood. This makes the final product more durable and uniform. Veneer also promotes resource efficiency, allowing for the use of smaller quantities of high-quality wood to achieve the desired appearance, thus preserving valuable timber.
Furthermore, veneer offers design flexibility with a wide range of wood species, colors, and grain patterns available. This extensive variety provides designers with the ability to create custom and unique finishes, enhancing the aesthetic versatility of wood products. Overall, veneer is a valuable material that combines decorative appeal, cost savings, stability, and efficient use of resources, making it a popular choice in furniture and cabinetry.
WOOD TERMINOLOGY FOR NOOBS
Adult (or Mature) Wood | Wood produced when the tree is already established that typically has a relatively constant cell size, stable physical behavior, and structural patterns that are well-developed. |
Air-dried (or Air-seasoned) | Wood that has been naturally seasoned in the open air and generally protected from the sun and rain throughout seasoning. |
Angiosperms (Angiospermae) | Botanical name for all plants (mostly deciduous) whose seeds are carried inside an ovary, including what are commonly referred to as hardwoods: those trees which are broad-leaved, flowing and fruit-bearing. |
Annual (or Growth) Rings | Concentric rings of wood added yearly to the growing tree in temperate zones. |
Arboreal | Related to or connected with trees. |
Arboriculture | The management of trees, or groups of trees, for their amenity value. |
Back Cut | The final cut when felling a tree, which is made on the opposite side to the direction of fall. |
Backsawn | Sawn so that the growth rings are inclined at less than 45 degrees to the wide face. A backsawn log is converted in such a way as to provide the maximum number of cuts tangential to the growth rings. |
Bast | The soft, fibrous tissue between the bark and the inner cell structure. |
Beating Up | Replacing trees that have died soon after planting. |
Billets | Small-diameter round timber cut to length. |
Blaze | To mark a tree with paint or by slicing off bark with an axe, either to earmark it for felling or to delineate boundary lines. |
Board Foot | Measurement unit common in timber trade equal to 144 cubic inches of wood. Board feet are calculated by multiplying the nominal thickness of a piece of wood in inches (T) by the nominal width in inches (W) by the actual length in feet (L) and dividing the product by 12. Board Feet = (T" x W" x L') / 12. |
Bole | The part of the trunk or stem of the tree from above the root butt to the first branch or limb, normally of timber size over 200mm in diameter. |
Bookmatching | The mirror-image effect obtained, especially in veneering, when adjacent sheets from a flitch are opened in the manner of a book, the back of one sheet being matched to the face of the next. |
Box the Heart | To leave a square piece at the heart when converting a log. |
Breast Height | The point at which the girth or diameter of a standing tree is measured on the highest side. The acronym 'DBH' stands for ' diameter at breast height'. Breast height is normally regarded as 1.37 meters above the ground. |
Bucking | Cutting trees into shorter lengths such as logs and cordwood. |
Bummer | A truck for hauling logs. |
Burl | A unique and irregular growth on a tree that results from a distortion in the normal wood grain pattern. It appears as a rounded, often knotted or gnarled lump on the trunk or branches of a tree. Burls are formed due to various factors, including genetic mutations, disease, insect infestations, or environmental stress. |
Butt | The base of a tree. |
Butt Cut | The first cut above the stump of a tree. |
Butt Log | The first log cut above the stump of a tree. |
Cambium | The layer of cells in a tree that divides to produce new tissue. |
Cheese Block | A wedge used to stop a log from rolling. |
WOOD SPECIES USED AT OHIO WOOD ART
Ohio Wood Art products are crafted from a wide variety of locally-sourced, reclaimed, and exotic wood species. Please refer to the chart below when considering wood species to specify for a custom or personalized piece you commission Ohio Wood Art to create. Some of these woods are known to cause sensitivities in some individuals; if you have a history of skin irritation or other reactions from exposure to a type of wood you should take that into account when shopping for Ohio Wood Art products.
SPECIES
GRAIN
JANKA
ORIGIN
SENSITIVITIES
