Hardwood
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The term hardwood is used to describe wood from non-monocot angiosperm trees and for those trees themselves. These are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.
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[edit] Properties
Hardwood contrasts with softwood, which comes from conifer trees. On average, hardwood is of higher density and hardness than softwood, although there is an enormous variation in actual wood hardness in both groups, with the range in density in hardwoods completely including that of softwoods; some hardwoods (e.g. balsa) are softer than most softwoods, while yew is an example of a hard softwood.
Hardwoods are more varied than softwood. There are about a hundred times as many hardwoods as softwoods. The dominant feature separating hardwoods from softwoods is the presence of pores, or vessels[1]. The vessels may show considerable variation in size, shape of perforation plates (simple, scalariform, reticulate, foraminate), and structure of cell wall (e.g. spiral thickenings).
[edit] Common hardwoods
Common deciduous European and North American hardwoods include the oaks (Quercus spp.), beech (Fagus spp.), ash (Fraxinus spp.), maple (Acer spp.) and cherry (Prunus spp.). Examples of European evergreen trees that yield specialty hardwoods (used in small volumes) include holly (Ilex aquifolium), boxwood (Buxus sempervirens) and Paduk holm oak (Quercus ilex). Important tropical hardwoods include teak (Tectona grandis), mahogany (Swietenia spp.), ebony (Diospyros spp.) and lauan (Shorea spp.). A very common hardwood found in the temperate rainforests is yellow cedar.(chamaecyparis nootkatensis)
[edit] Applications
Hardwoods are employed in in a large range of applications including: construction, furniture, flooring, cooking, utensils, etc. Solid hardwood joinery tends to be expensive compared to softwood. In the past, tropical hardwoods were easily available but the supply of some species such as Burma teak and mahogany is now becoming restricted due to overexploitation. Cheaper "hardwood" doors, for instance, now consist of a thin veneer bonded to a core of softwood, plywood or medium-density fibreboard (MDF). Hardwoods can also be used in a variety of objects but mainly for furniture or musical instruments because of their density. Paduk is a hardwood commonly used for solid wood flooring Different species of hardwood lend themselves to different end uses or construction processes. This is due to the variety of characteristics apparent in different timbers including, density, grain, pore size, growth pattern, wood fibre pattern, flexibility and ability to be steam bent. For example, the stepped wood fibre pattern, typical of Elm, makes it ideal for the making of chair seats where the driving in of legs and other components can cause splitting in other woods.
[edit] Cooking
Because hardwoods are generally denser, they contain more calories/volume. This makes hardwoods such as oak, cherry, and apple ideal for camp fires, cooking fires, and smoking meat as they tend to burn hotter and longer than softwoods such as pine or cedar.
[edit] See also
[edit] References
- ^ CRC Handbook of Materials Science, Vol IV, pg 15
[edit] Further reading
- Schweingruber, F.H. (1990) Anatomie europäischer Hölzer—Anatomy of European woods. Eidgenössische Forschungsanstalt für Wald, Schnee und Landscaft, Birmensdorf (Hrsg,). Haupt, Bern und Stuttgart.
- Timonen, Tuuli (2002). Introduction to Microscopic Wood Identification. Finnish Museum of Natural History, University of Helsinki.
- Wilson, K., and D.J.B. White (1986). The Anatomy of Wood: Its Diversity and variability. Stobart & Son Ltd, London.
[edit] External links
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