ENCYCLOPEDIA OF WOOD
SOFTWOODS AND HARDWOODS
rees are roughly divided into softwoods and hardwoods, but the terms are inexact: Some hardwoods, such as basswood or aspen, for example, are softer than North American softwoods like longleaf pine or Douglas-fir.
The type and shape of a tree’s leaves are more accurate indicators of a particular wood's identity. Softwoods include evergreen conifers with needlelike leaves, while hardwoods comprise broad-leaved deciduous, or leaf-shedding, trees. But it is at the microscopic level that the true differences between softwoods and hardwoods can be seen. Softwoods are composed mainly of tra - cheids, dual-purpose cells which conduct the sap up through the trunk and
provide support. Hardwoods, which are believed to have evolved later, have narrower, thicker-walled fiber cells for support and large-diameter thin-walled vessels for sap conduction. These cells determine the texture of a tree’s wood.
In spring, when there is abundant moisture and rapid growth of early - wood, the tracheid cells in softwoods have thin walls and large cavities to conduct the sap. The result is relatively porous wood. As latewood develops in the latter part of the growing season, the tracheids begin to form thicker walls, creating denser wood.
In hardwoods such as oak or ash, most of the vessels develop in the early - wood, resulting in uneven grain. These
species are called ring-porous. With diffuse-porous hardwoods such as maple, the vessels are distributed more evenly in the earlywood and latewood. Some species, such as walnut, exhibit a more gradual transition from earlywood to latewood and are termed semi-ring - porous or semi-diffuse-porous.
The differences in cell structure between softwoods and hardwoods become apparent when a stain is applied. In softwoods, the light, porous earlywood absorbs stain more readily than the dark, denser latewood—in effect reversing the grain pattern like a photographic negative. Hardwoods, however, absorb stain more evenly, enhancing the grain pattern.
CELL STRUCTURE OF SOFTWOODS AND HARDWOODS
A microscopic view
The differences between softwood and hardwood are readily apparent when viewed under a microscope's magnification. The cell structure of softwoods (above, left) is much simpler than that of hardwoods. Almost all softwood cells are long, thin tracheids, which support an unbroken column of sap that can tower more than 200 feet. The tracheids in latewood become thicker-walled than those in earlywood. In hardwoods
(above, right), the sap is conducted through vessels, a series of tubelike cells stacked one atop the other. Support for the trunk is provided by fiber cells. In the ring-porous hardwood shown, vessels are more prominent in earlywood; fibers are the predominant cell type in latewood. In both hardwoods and softwoods, storage cells for carbohydrates and starch make up the remaining non-vascular wood tissue.
|
A ROSEWOOD BY ANY OTHER NAME...
wood instead, since both belong to the rosewood family and are native to Brazil. In fact, there are several genuine rosewoods, such as East Indian rosewood and cocobolo, that cost much less than the Brazilian variety and are easier to find. However, they might not fit the bill for a guitar-maker. Other species, such as bocote, bubinga and padauk, are often sold as rosewood substitutes, but do not look at all like Brazilian rosewood.
To avoid confusion, it is helpful to refer to certain woods by their botanical names. Brazilian rosewood is Dalbergia nigra, and a guitar-maker who requests it by that name will not be disappointed.
This scientific naming system was developed more than 200 years ago by Swedish botanist Carl Linnaeus.
|
|
|
For the practicing woodworker, calling a piece of wood by its common name seldom creates confusion. If you ask for a few planks of white oak at a lumber yard, for example, there is no reason why you should not get what you requested. But with some species, particularly exotics that must be purchased by mail-order, identities can be less certain. Common names are misleading when trees with different characteristics share the same name, or when the same species has different common names in separate localities.
Suppose you wanted samples of a very rare and expensive species like Brazilian rosewood, a black-streaked, dark brown wood often used in the making of superior-quality guitars.
A supplier could in good conscience send you pieces of kingwood or tulip-
|
|
|
As shown below, in a botanical analysis of Brazilian rosewood, Linnaeus’ now universally accepted scheme classifies plants into the various taxonomic groups of phyla, classes, orders, families, genera and species. Almost all trees belong to the spermatophyta phylum, with hardwoods in the angiospermae sub-phylum and the dicotyledonae class, and softwoods belonging to the gymnosper - mae subphylum.
A botanical breakdown
of Brazilian rosewood Phylum: Spermatophyta Sub-phylum: Angiospermae Class: Dicotyledonae Order: Rosales Family: Leguminosae Genus: Dalbergia Species: Nigra
|
|
|
|
|
In addition to lumber and manufactured boards, trees provide a cornucopia of raw materials for products such as rolls of newsprint (left). For centuries, people have extracted such natural products as cork, rubber, gum, medicine, spices, drugs, oils, charcoal, camphor and resins. The cellulose fiber found in trees is used in the production of plastics and lacquers as well as wood pulp. Coniferous trees supply turpentine and resins, which are used in paints, inks and finishes. Modern chemistry has unlocked still more of wood’s hidden treasures, finding ways to remove such disparate products as glues, poisons and artificial vanilla.
|
|
|
|
(H) Botanical Name: Cordia dodecandra A stunning, dark wood, ziricote is easy to work and can be broughtto a very smooth finish. Though difficult 5o dry, once this is achieved …
(И) Botanical Name: Microberlinia brazzaviWeneie Distinctive in appearance, zebrawood comes from two species of large trees found mainly in Cameroon and Gabon, West Africa. While it is usually seen as …
(H) Botanical Name: Salix nigra While its European cousin is used most notably in cricket bats, black willow is most frequently used in North America by school woodworking shops; it …
