When timber is burnt in the wood fire over a depth of about 15 mm, the process of treatment is known as __________.
Timber Preservation Methods
Timber preservation involves treating wood to protect it from decay and insect attack, thereby increasing its lifespan. Methods range from simple, traditional techniques to complex industrial processes. The choice of method depends on the type of timber, its intended use, and the level of protection required.
📝 Detailed Analysis of the Options
(b) Rueping process
This is an "empty-cell" pressure treatment process for preservation. It uses an initial phase of compressed air to ensure that after the preservative is forced in, the expanding air pushes out the excess, leaving only the wood cell walls coated. It's a chemical pressure treatment, not a burning process.
(c) Bethel process
This is a "full-cell" pressure treatment for preservation. It uses an initial vacuum to remove air, allowing the preservative to completely fill the wood cells. It provides maximum protection but is more expensive. It is also a chemical pressure treatment.
(d) Boucherie process
This is a preservation method for green (unseasoned) timber. It uses hydrostatic pressure to replace the natural sap with a water-borne preservative. It does not involve burning.
(a) Charring
This is the correct answer. Charring is a traditional and simple method of preservation where the surface of the timber is burnt over a fire to a depth of about 15 mm. The resulting layer of charcoal is resistant to moisture, fungi, and insects. While it is considered a crude or lower-quality method and is not used for valuable timber, it is effective and economical for protecting the ends of timber posts, poles, and piles that are to be embedded in the ground.
📊 Comparison of Preservation Processes
| Process | Method | Primary Use |
|---|---|---|
| Charring | Burning the surface | Protecting underground posts/piles |
| Rueping Process | Chemical pressure treatment (empty-cell) | General preservation of seasoned timber |
| Bethel Process | Chemical pressure treatment (full-cell) | Heavy-duty preservation of seasoned timber |
| Boucherie Process | Sap displacement in green timber | Preservation of unseasoned poles/posts |
💡 Study Tips
- Charring = Burning: This is a direct and easy association to remember. Charring is the act of creating charcoal on the wood's surface.
- Think of Fence Posts: The most common application for charring is to protect the part of a wooden fence post that goes into the ground.
- Distinguish from Chemical Processes: Remember that Rueping, Bethel, and Boucherie are all chemical treatments involving preservatives, whereas charring is a physical process using fire.