QUALITIES OF GOOD TIMBER

Following are the characteristics or qualities of a good timber:

1. APPEARANCE: A freshly cut surface of timber should exhibit hard and shining appearance.
2. COLOUR: The colour of timber should preferably be dark. The light colour usually indicates timber with low strength.
3. DEFECTS: A good timber should be free from serious defects such as dead knots, flaws, shakes, etc.
4. DURABILITY: A good timber should be durable. It should be capable of resisting the action of fungi insects, chemicals, physical agencies and mechanical agencies. If wood is exposed to the actions of acid and alkalies foe a prolonged period it is seriously damaged. The weak alkali and acid solutions usually do not affect wood to a considerable extent. 
   
5. ELASTICITY: This is the property by which timber returns to its original shapes when load causing its deformation is removed. This property of timber would be essential when it is to used for bows, carrying shafts, sports goods etc.
6. FIBRES: The timber should have straight fibres.
7. FIRE RESISTANT: The timber is a bad conductor of heat. A dense wood offers good resistant to the fire and it requires sufficient heat to cause a flame. The heat conductivity of wood is low and it depends on various factors such as porosity, moisture content, surrounding temperature, orientation of fibres, bulk densdity etc.  
8. HARDNESS: A good timber should be hard i.e. it should offer resistant when it is being penetrate by another body. The chemicals present in heart wood and density of wood impart hardness to the timber. The mere resistance offered to chisel or saw does not usually indicate hardness of timber.
9. MECHANICAL WEAR: A good timber should not deteriorate easily due too mechanical wear or abrasion. This property of timber would be essential for places where timber would be subjected to traffic e.g. wooden floors, pavements etc.
10. SHAPE: A good timber should be capable of retaining its shape during conversion or seasoning. It should not bow or warp or split.
11. SMELL: A good timber should have sweet smell. An unpleasant smell indicates decayed timber.
12. SOUND: A good timber should give out a clear ringing sound when struck. A dull heavy sound when struck indicates decayed timber. The velocity of sound in wood is 2-17 times greater than that in air and hence the wood may be considered high in sound transmission. The sound conductivity is faster along the fibres is lower in the radial direction and is slowest along the chord of a cross-section.
13. STRENGTH: A good timber should be strong for working as structural member such as joist, beam, rafter etc. It should be capable of taking loads slowly or suddenly. It should also possess enough strength in direct and transverse directions.
14. STRUCTURE: It should be uniform. The fibres should be firmly added. The medullary rays should be hard and compact. The annual rings should be regular and they should be closed located. 
15. TOUGHNESS: A good timber should be tough i.e. it should be capable of offering resistant to the shocks due to vibrations. This property of timber would be essential when it is to be used for tool handles, parts of motor cars and aeroplanes etc. 
16. WATER PERMEABILITY: A good timber should have low water permeability which is measured by the quality of water filtered through a unit surface area of specimen of wood. The water permeability is greater along the fibres than in other directions and it depends on initial moisture content, character of cut, type of wood, width of annual rings, age of wood etc.
17. WEATHERING EFFECTS: A good timber should be able to stand reasonably the weathering effects. When timber is exposed to weather its colour normally fades and slow turns grey. A good timber should show the least disintegration of the surface under adverse weather conditions such as drying and wetting, extreme heat and extreme cold etc.
18. WEIGHT: The timber with heavy weight is considered to be sound and strong.
19. WORKING CONDITION: The timber should be easily workable. It should not clog the teeth of saw and should be capable of being easily planed or made smooth.