Preservation of Timber

Wood preservation means treating wood with solutions which make it poisonous to fungi and insects. Some timbers, especially the hardwoods from tropical forests, are naturally durable' and will resist attack by either fungi or insects. Generally speaking the heartwood of all timbers is more durable than the sapwood. This is because the cells and tubes in the outer rings of the trunk, and especially the cambium layer which is just underneath the bark, are open to allow water up from the roots and food produced in the leaves to pass down to feed the tree. The cells of the inner rings are closed, as they are no longer needed for the transport of water and food. This means that the inner heartwood does not allow fungi and insects enter as easily as the open cells of the outer sapwood. However treating any timber with a preservative will make it resistant to attack by fungi and insects. Also, using preservative treated home-grown softwood timber instead of tropical hardwoods is one important way of helping in the conservation of the tropical forests, There are 3 classes of wood preservative: (I) Tar oil type (2) Organic solvent type (3) Water-borne type Tar Oils: Creosote is the most widely used tar-oil preservative. It is extracted from coal tar. Creosote is cheap but has a heavy odour and cannot be over-painted. Generally it is only suitable for outdoor use, fencing, telegraph poles, railway sleepers. Organic Solvents: This type of preservative is a mixture of poison dissolved in an industrial alcohol. The alcohol soaks into the timber very easily (more easily than water), carrying the poison with it. With time the alcohol will naturally evaporate leaving the poison embedded in the wood. Organic solvent preservatives have a faint odour. They can be bought clear or coloured which may be useful if you want to show which timbers have been treated. Familiar trade-name products such as Protim and Cuprinol are organic solvent type preservatives. Water-borne preservatives: This type of preservatives works in the same way as the organic solvents except that the poison is dissolved in water. The timber to be treated must be soaked for a longer time than with the organic solvents and must also be redried. These preservatives are odourless and colourless.

Materials Wood

Insect Attack