.......... is characterised due to swelling caused by the growth of layers of sapwood over wounds after a branch has been cut off in an irregular manner.
🌳 Understanding Defects in Timber
Defects in timber are abnormalities or irregularities that reduce its strength, durability, appearance, and overall value. These can arise from natural forces (like wind and insects), during the tree's growth, or due to improper seasoning and conversion after felling. The question describes a defect caused by an external injury.
📝 Detailed Analysis of the Options
(b) Shakes
Shakes are cracks or separations in the wood that occur along the grain, usually separating the annual rings. They are caused by factors like wind, frost, or excessive heat during the tree's life. They are internal cracks, not external swellings.
(c) Foxiness
Foxiness refers to a reddish-brown or yellowish stain or discoloration in the wood. It's an early stage of decay caused by fungal activity, typically occurring when timber is stored without proper ventilation.
(d) Knots
Knots are the bases of branches or limbs that become embedded within the tree's trunk as it grows. While they are a natural feature, they disrupt the wood grain, creating a hard, dark, and often loose section that can weaken the timber.
(a) Rind gall
This is the correct answer. A rind gall is essentially a scar or callus that forms on a tree. When a branch is cut off improperly or the tree suffers an external wound, it tries to heal itself. This healing process involves new layers of sapwood growing over the wound, resulting in a characteristic swelling or bulge on the surface. This perfectly matches the description in the question.
📊 Comparison of Timber Defects
| Defect | Description | Primary Cause |
|---|---|---|
| Rind Gall | Swelling or bulge on the surface. | Growth of new wood over an irregular wound. |
| Shakes | Internal cracks or separations along the grain. | Natural forces (wind, frost) during growth. |
| Foxiness | Reddish-brown discoloration or stain. | Fungal decay due to poor storage. |
| Knots | Dark, hard base of a branch embedded in the trunk. | Natural tree growth process. |
💡 Study Tips
- Rind Gall = Wound Swelling: Associate "rind gall" with the tree's healing process over a wound, causing a bulge.
- Knots vs. Galls: Knots are natural (from branches), while galls are from external injuries. Knots are embedded *in* the wood; galls are swellings *on* the wood.
- Shakes are Splits: Remember that shakes are internal splits or cracks, not external growths.