Yes, generally speaking, dry wood is harder than green wood.
Understanding Wood Hardness and Strength
Wood is a natural material whose physical properties, including hardness and strength, are significantly affected by its moisture content. When wood is "green," it contains a large amount of water within its cell structure. As wood dries, this water is removed, causing changes at a cellular level that influence its mechanical properties.
According to the provided reference, "Dried timber is stronger than green timber in most strength properties." Strength properties encompass various ways wood resists force, including compression, tension, bending, and shear. While "hardness" specifically refers to resistance to indentation or scratching, it is closely related to other strength properties, particularly compression strength.
When wood dries, the cell walls become denser and more rigid as the water is removed. This increased density and rigidity contribute to greater resistance against deformation, impact, and wear – which translates directly to increased strength and, consequently, increased hardness.
Why Drying Matters for Wood Properties
The process of drying wood, often called seasoning, is crucial for preparing timber for various applications.
- Improved Strength and Hardness: Dry wood can bear heavier loads and resists surface damage better than green wood.
- Dimensional Stability: Drying reduces shrinking and swelling, leading to more stable wood products less prone to warping or cracking.
- Better Finish Application: Paints, stains, and varnishes adhere and perform better on dry wood.
- Enhanced Preservative Penetration: As noted in the reference, "Timbers for impregnation with preservatives have to be properly dried if proper penetration is to be accomplished, particularly in the case of oil-type preservatives." This is because the spaces previously occupied by water become available for preservatives to enter.
- Reduced Susceptibility to Decay and Insects: Lower moisture content makes wood less hospitable to fungi and insects.
Comparing Green vs. Dry Wood
| Property | Green Wood | Dry Wood | Implication |
|---|---|---|---|
| Hardness | Lower (Softer) | Higher (Harder) | Resists dents and scratches better. |
| Strength (Overall) | Lower | Higher (as per reference) | Can support more weight/resist more force. |
| Moisture Content | High | Low | Less prone to decay and dimensional change. |
| Density (effectively) | Lower (water adds weight) | Higher (actual wood substance) | Denser structure contributes to hardness. |
| Preservative Uptake | Poor | Good (as per reference) | Allows effective treatment for durability. |
This table illustrates the general differences. The exact degree of change varies depending on the specific wood species and the final moisture content achieved after drying.
In conclusion, the process of drying wood significantly improves its mechanical properties. By removing moisture, the wood becomes stronger in most properties, which includes a corresponding increase in hardness. This makes dry wood the preferred material for most structural and finishing applications.
