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                                                                  LOGGING

About Logging

Logging is the process of harvesting trees, sawing them into appropriate lengths (bucking) and transporting them (skidding) to a sawmill. The different phases of this process vary with local conditions and technology.

In colder regions, trees are felled by axe in winter and transported by a sledge drawn by oxen, mules, or horses to a frozen river. After the spring thaw, the logs are floated down the river to the sawmills.

In the 19th century logging was a hand process. But today, in some parts of the world it has been mechanized, trees are felled by crosscut saw or power-driven chain saw. Even trees of relatively young plantations are felled by a machine that cuts the entire tree in one bite. Trees are then cut into standard lengths and skidded to the mill by truck or tractor or conveyed to a central point by cable, either high above the ground (high-lead and overhead skidding) or along the ground (ground line skidding). Helicopters and balloons are also used to transport logs.

Local conditions may dictate uncommon logging methods. In India, teakwood trees are felled by girdling (making a circular cut around the tree through the outer bark and cortex to interrupt the circulation of water and nutrients) and harvested several years later. Then, as is also common in Nigeria, they may be floated down the river by raft. In several Asian countries, timber is transported by elephants.

Types of Logs

Laminated Logs
- formed by gluing wooden boards together & shaping them up into log forms by machines. These logs have a moisture content of less than 18%; therefore, they can be coated immediately with a Sikkens system.

Kiln or Air Dried Logs - are dried by air exposure or in kilns. Generally, their moisture content is below 18%; however after construction, some logs may have moisture content higher than 18%. Therefore, it is recommended to allow a six months drying period before applying Sikkens system. If the moisture content of the log is unknown, follow the application procedure for green logs.

Green, Wolmanized Timber and Pressure Treated Logs - these have a moisture content of 18% or higher. Therefore, they should not be coated with a solvent borne, film-building coating until the moisture content has been reduced to 18%, or less. Wolmanized timber or pressure treated logs have all been treated with various chemicals and forced into the wood under pressure thereby protecting the wood from fungus and from rotting. The moisture content of these logs is normally above 18%, therefore, a minimum drying period of 6 months must be observed before coating them.