Timber which are slow and difficult to season free from defects, are classified as _____ based upon their behaviour to cracking and splitting during normal air-seasoning practice.
- ALow refractory
- BHigh refractoryCorrect
- CModerate refractory
- DNull refractory
Solution
Concept
Timber is classified by how easily it cracks and splits during air seasoning: highly refractory, moderately refractory and non-refractory.
Step-by-step solution
1. Timber is grouped by its behaviour to cracking and splitting during air seasoning. 2. Highly refractory (Class A): slow and difficult to season free from defects. 3. Moderately refractory (Class B): can be seasoned free from defects in a fairly short time with a little protection. 4. Non-refractory (Class C): can be seasoned quickly free from defects. 5. So the answer is high refractory.
Explanation
Highly refractory timber dries slowly and easily develops cracks and splits. It must be seasoned slowly with protection from fast drying conditions. That is why timber that is slow and difficult to season free from defects is called high refractory.
Why the other options are wrong
A: There is no 'low refractory' class. Easy-to-season timber is called non-refractory. C: Moderately refractory timber can be seasoned free from defects in a fairly short time with a little protection. D: 'Null refractory' is not a standard term.
Shortcut
Hard to season means highly refractory. Easy to season means non-refractory.
Common mistake
Thinking 'refractory' means heat or fire resistance. Here it means resistance to easy seasoning.
Correct answer: B) High refractory