Timber is the name given to wood that has been prepared for the purpose of building or carpentry. Preparation includes the drying and sometimes treatment of this wood.
There are a few methods of drying wood in New Zealand including:
- Ambient temperature drying – air drying and forced air drying.
- Low temperature dryers (up to 60C, usually 40-50C) – heated forced-air dryers and low temperature kilns including most heat pump dryers (dehumidifiers).
- Conventional kilns (usually temperatures of 60-80C for New Zealand pine).
- Accelerated conventional-temperature kilns operating at temperatures of 80-100C.
- High temperature kilns (temperatures above 100C, usually 120C or higher).
- Vacuum drying, which is new to New Zealand, offers the potential of rapid drying and minimising discoloration of high quality lumber.
“Kiln drying is an industrial unit operation used to accelerate the drying of wood. A wood drying kiln is an enclosed space where air speed, temperature and humidity are controlled. Natural air-dying of wood can take weeks, while a wood drying kiln can complete the process in less than a day”¹
The benefit of kiln drying the timber is that it is dried in a controlled environment, has rigorous testing, and is extremely quick giving a higher quality end product. Bugs and insects are also killed during the drying process. Therefore it can be more cost effective and less likely to have distortion, staining or drying stresses (i.e. warping or bowing).