Hardwood

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A small stand (group) of hardwood trees.

Hardwood is wood from deciduous trees and broad-leaf evergreen trees.[1] All hardwoods are angiosperms (flowering plants) which are the most assorted and largest group of land plants. Hardwoods all have enclosed nuts or seeds.[2] Hardwood is in contrast to softwood which come from conifers, cone bearing seed plants. Hardwoods are not always harder than softwoods, Balsa wood being a notable exception.[3] Hardwoods have a more complex internal structure than softwoods. It is mostly solid wood fibers with hollow tubes (vessels) used to supply water to the tree. Softwoods have a structure that looks like many drinking straws bound together all of which are used to supply water to the tree. Hardwood trees are more varied than softwoods and there are about 100 times more species of hardwood than there are softwoods.[2]

Introduction[change | change source]

Hardwoods are a type of tree that produce a dense wood. Unlike softwoods, hardwoods usually have broad leaves. Deciduous hardwoods undergo a colour change, usually once a year, going from green to yellow, then red/purple and then brown. Except for brown, these colours are always present in the leaves while they are green but are masked by the large amounts of chlorophyll which is green. In a green leaf, water drawn up from the ground, carbon dioxide from the air and sunlight combine with water to make molecules of glucose which the tree uses as energy to grow. In some cases such as the maple trees glucose gets trapped inside the autumn leaf and sunlight and cool weather turns the glucose into reds and purples. The brown colours seen in autumn leaves are due to waste products left inside the leaf.[4] Hardwoods all have enclosed nuts or seeds, where softwoods are Gymnosperms, naked seed plants.[2] Hardwood species are much more in number than softwoods, there being about 100 times more species of hard than softwoods.[2]

Properties[change | change source]

The difference between hard and soft wood under a microscope; oak on top, pine underneath.[2]
SEM image (top) and Transmission Light Microscope image (bottom) of vessel elements in Oak

Each species of hardwood has its own set of properties, however they have some properties in common. Hardwoods normally have broad leaves and come from deciduous or broad-leafed evergreen trees. Hardwoods grow slower than softwoods. Evergreen softwoods grow faster than deciduous hardwoods, and can grow to a larger size.[5] Hardwoods are excellent for carving. One of the hardest hardwoods is black ironwood which is recognized by the Guinness Book of World Records as the heaviest wood.[6] Ironwoods are so dense that they sink in water rather than float as other woods do.[7]

The properties of the wood are caused by its structure. Hardwoods have a denser structure, which is the reason they are usually harder and heavier. Hardwood has xylem vessels which are used to transport water. Their cell walls are strongly lignified: lignin is a hard material used to support plants above the surface. The quantity of lignin is probably the main factor in their hardness.

Softwoods have a vascular structure which looks similar to a bunch of drinking straws held together. They also have lignin, but of a slightly different type, and less of it than most hardwoods.

Species of hardwood[change | change source]

Common species of hardwood found in the USA,[8] Many species are also found in other areas of the world. This is not a complete list of all hardwood trees.

Alder Ash Aspen Basswood Beech Birch Cherry
Cottonwood Elm Hackberry Hickory Hard Maple Pecan Red Oak
Sap Gum Sassafras Soft Maple American Tulipwood Walnut Willow White Oak

Uses of hardwood[change | change source]

A mahogany sofa showing detailed carving

Hardwoods are often used to make items that get used a lot because of their density. These items include furniture, flooring, and utensils. They are also used in construction.[2] Hardwoods are also less likely to decay or rot than softwoods.[2] Furniture made by hardwood joinery is more expensive than that made from softwoods.[2] Utensils for use in preparing food can include things such as the vessel in the gallery below used by the Ede people to grind corn and grains for food. Other utensils include; spoons, chopsticks, bowls, plates and cups. Because of the dense nature of the wood used such a vessel can be used for many years without breaking. Other examples include the handle of the Luzon knife seen in the gallery. Because of the nature of sound transmission provide a good wood for musical instruments such as violins, guitars, pianos and hand drums such as the Djembe drum pictured in the gallery below. Flooring is often made of hardwood because it can stand up to years of people walking on it with their shoes. An example is the flooring made from tiger-wood seen in the gallery below. Hardwoods are also used to make wood veneers to glue over other, cheaper woods, making them less expensive than solid hardwood while still giving them the appearance of a particular species of wood. This has become a common way of using tropical hardwoods that have a limited supply of trees due to deforestation occurring in many tropical countries.[9] In Europe, hardwoods account for 29% and softwoods 71% of wood consumption.[10] Hardwood has very short fibers about 1mm in length and is so also used to make fine paper such as writing paper, tissue, and printing paper.[10] Paper with longer fibers such as paper bags, cardboard and shipping containers is made of softwoods.

Gallery[change | change source]

A variety of objects made from different types of hardwood.

Other pages[change | change source]

Other websites[change | change source]

References[change | change source]

  1. Izzy (02-12-2008). "Hardwoods". Camberwell Material Library. http://cltad.arts.ac.uk/groups/camberwellmateriallibrary/wiki/c5e36/Hardwoods..html. Retrieved October 15, 2011.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Coombes, Allen J. (2010). The illustrated Encyclopedia of Trees and Shrubs. Salamander Books. ISBN 1840651628.
  3. "Hardwoods". www.mr-dt.com. http://www.mr-dt.com/materials/hardwoods.htm. Retrieved October 16, 2011.
  4. "Autumn Leaves and Fall Foliager Why Do Leaves Fall Colors Change?". Science Made Simple. http://www.sciencemadesimple.com/leaves.html. Retrieved October 16, 2011.
  5. "Year 10 Manufacturing (Resistant Materials)". Design Technology Department. http://www.design-technology.org/CDT10woodslesson.htm. Retrieved October 16, 2011.
  6. "Botanical Record Breakers - Part 1 of 2". Palomar College. 06-03-2011. http://waynesword.palomar.edu/ww0601.htm. Retrieved October 17, 2011.
  7. W.P. Armstrong (04-28-2010). "Hardwoods Trees & Shrubs With Dense, Hard Wood". Palomar College. http://waynesword.palomar.edu/plsept99.htm. Retrieved October 17, 2011.
  8. "About U.S. Hardwoods". American Hardwood Export Council. 2002. http://www.ahec.org/hardwoods/guide/index.html. Retrieved October 16, 2011.
  9. "Words into Action". The Tropical Forests Trust. 03-2011. http://www.tft-forests.org/downloads/get/?d=3465. Retrieved October 17, 2011.
  10. 10.0 10.1 "Pulping properties of hardwoods and softwoods". Paper Online. http://www.paperonline.org/paper-production/pulping/pulping-properties-of-hardwoods-and-softwood. Retrieved October 17, 2011.