Atmospheric drying of wood, also known as air drying, is a method used to reduce the moisture content of timber, particularly for certain coniferous wood species that are intended for use without being longitudinally sawn.
This process is employed to prevent insect infestations and to facilitate the relatively rapid drying of wood materials. Here’s a more detailed explanation of atmospheric wood drying:
- Purpose: The primary objective of atmospheric wood drying is to lower the moisture content of the wood to a suitable level for various applications, typically in the range of 18-22%. This level of moisture is considered optimal for preventing fungal decay processes in the wood while still making it workable for further processing.
- Bark Removal (Peeling): To facilitate drying and reduce the risk of insect infestation, the bark is often removed from the wood. Bark can trap moisture and provide a suitable environment for insects and fungi, so its removal is a common practice in atmospheric drying.
- Drying Environment: Atmospheric drying takes place in stacks or piles of lumber, typically placed in an open, well-ventilated area. Unlike kiln drying, which involves controlled heating, atmospheric drying relies solely on the natural environmental conditions, including temperature, humidity, and airflow, to reduce the wood’s moisture content.
- Advantages: The main advantage of atmospheric drying is its low cost. Since it doesn’t require sophisticated equipment or energy-intensive heating, it is a cost-effective method. Additionally, it can be environmentally friendly as it doesn’t consume substantial energy resources.
- Drawbacks: Atmospheric drying has some limitations. It is seasonal and depends on weather conditions. Drying cannot occur effectively during the winter months or in regions with adverse weather conditions. The process can also be time-consuming, with drying times varying depending on the wood species, initial moisture content, and environmental factors. Furthermore, there is a possibility of the wood developing cracks or checking during the drying process due to differential moisture loss from the surface and interior.
In summary, atmospheric wood drying is a cost-effective method used to reduce the moisture content of wood for various applications. While it has its advantages, such as low cost, it also comes with limitations related to seasonality and potential surface cracks in the wood. The choice of wood drying method depends on factors like the type of wood, intended use, and available resources.