You can't dry a whole tree; instead, you dry the timber after it has been cut into lumber. Here are the primary methods for drying timber:
Methods of Drying Timber
The two most popular methods of drying timber are air drying and kiln drying. Both methods aim to reduce the moisture content of the wood to make it suitable for construction and other uses. Here’s a closer look at each method:
1. Air Drying
Air drying involves stacking timber in a way that allows air to circulate freely around each piece. This method is typically done outdoors and relies on natural air movement and temperature to gradually reduce the moisture content.
- Process:
- The timber is stacked off the ground on supports called "stickers."
- Stickers create gaps between the layers of wood, promoting airflow.
- The stacks are often covered to protect from direct rain and sun, but allow air to move freely.
- Drying time depends on factors such as wood species, thickness, and the environment's climate and relative humidity.
- Pros:
- Lower energy costs compared to kiln drying.
- Results in more stable and stress-free wood.
- Cons:
- Much slower process than kiln drying.
- Susceptible to varying weather conditions, which can affect the drying rate.
- Air-dried wood contains slightly higher moisture content than kiln-dried wood.
2. Kiln Drying
Kiln drying is a more controlled and accelerated method where timber is placed inside a specialized kiln, where temperature, humidity, and airflow are carefully managed.
- Process:
- Timber is loaded into the kiln on carts or racks.
- Heated air is circulated around the wood.
- Kiln operators control the temperature, humidity, and airflow for a specific drying schedule to dry wood effectively.
- Kiln drying can take a few days to weeks to complete depending on the species, size, and final moisture content needed.
- Pros:
- Significantly faster drying time compared to air drying.
- Achieves a lower and more consistent moisture content, making it less likely to warp or shrink.
- The controlled environment minimizes the risk of pests and mold.
- Cons:
- Higher energy costs compared to air drying.
- Requires specialized equipment.
- Can cause internal stresses if not done correctly and therefore result in defects in the timber.
Summary Table of Timber Drying Methods
| Method | Drying Speed | Moisture Content | Cost | Equipment Needs | Environmental Factors |
|---|---|---|---|---|---|
| Air Drying | Slower | Moderate | Lower | Sticks and cover | Influential |
| Kiln Drying | Faster | Lower | Higher | Kiln, and related equipment | Controlled |
Air dried wood contains less moisture than green wood but has more moisture than kiln-dried wood. Ultimately, the method chosen depends on the desired outcome, the type of wood, time constraints and available resources.
