WOOD IDENTIFICATION KEYS
orrectly identifying an unfamiliar wood sample out of thousands of possibilities requires close observation, and a thorough knowledge of wood and its properties. But as a practical matter, the possible choices are usually limited to several familiar species, and a commercially available set of labeled wood samples, such as the one shown at right, may include a piece that matches the wood you are attempting to identify. Most often, however, you will need to record the features of a sample, then use a wood identification key from a book to make sense of your results.
An identification key is essentially a master list of woods and their properties that serves as a cross-reference to link the features of a particular sample to a species name. Some keys require that you compare their entries against features that are visible to the naked eye or with a lOx magnifier, while others demand that you note microscopic details. Still other keys are based on the user having wide-ranging sensory information about the wood, including its color, odor and texture, and the bark and leaf shape of the tree from which it came.
Using a key is like climbing the branches of a tree. You are asked to answer a series of paired statements, choosing the one that best describes the wood in question and proceeding to the next pair indicated. At each statement, the user forks onto a different branch
until reaching a leaf that identifies the sample. The first statement may involve the texture of the wood. If the wood is porous, for example, you are sent to one set of statements; if it is non-porous, you jump to a different set of statements. You continue this way, flipping from page to page in a book, as each answer gradually reduces the choices. Finally, the search is narrowed to a single species.
Avoid keys that try to cover every wood species in the world; they will prove too general. Choose one that describes trees in a specific region, such as North American softwoods or tropical hardwoods. Several classic keys can be found in woodworking books; check your local library or bookstore. Some public agencies (below) also offer wood identification services.
USING A WOOD IDENTIFICATION KEY
Here is an example of how a typical wood identification key works. In this case, we are starting with a plain-sawn board of an unknown wood. The first step is aimed at narrowing the investigation to either the hardwood or the softwood portion of the key. You examine your sample with a hand lens and observe that it has vessels and is porous; according to your key, it is a hardwood. Next, you must determine whether the wood is ring - or diffuse-porous: You notice that its earlywood is not sharply defined; you are told that it is diffuse-porous. The next features to examine are the rays. Seen in the tangential view of your sample, the rays are relatively narrow and uniform in width. This observation leads to another concerning the size of the pores in the growth rings. Since the pores in the earlywood of your sample are larger than those in the latewood, this indicates that you have a semi-diffuse-porous wood. Next, you examine the distribution of the pores in the growth ring. If they were unevenly distributed, the key would identify your sample as tanoak. Instead, the pores in your sample are evenly distributed. You must then evaluate the storage cells in the latewood. Seeing that they are present in a fine, unbroken line, you are directed to determine the color of the heartwood. If it were chestnut-brown or chocolate, you would have a piece of black walnut or butternut.
But since the heartwood is brown to yellow-brown, you have either water hickory or persimmon. Since the rays of your sample are stacked vertically, creating ripple marks, the key leads you to the end of your quest: the sample is persimmon.
Wood with stacked rays,.forming ripple marks extending afross the grain Ж/hen tangential ' section of wood is viewed: Persimmon
Heartwood brown to yellow-brown
Latewood storage cells appear in fine, continuous line s
Pores unevenly distributed throughout growth ring and found in dusters separated by sections of fibrous tissue: Tanoak
Pores in the earlywood larger than those in the latewood; transition gradual (semi-diffuse-porous)
Pays broad and visible
Wood ring-porous (earlywood sharply defined); earlywood pores larger than latewood pores and visible to the naked eye