Preservation of Wood

Timber is gradually destroyed if used under the ordinary atmospheric conditions for a long period of time. It should be noted that serviceable life of wood also depends on the species and the situation in which wood is used.

For example, sound wood was found in the Egyptian tombs. The archaeologists stated that the preservation of wood could be explained easily: the wood had been very well protected from the surrounding atmosphere. Even nondurable species would last for many years under such conditions.

The sound stumps of western red cedar stay in the forest for several centuries. But this fact is explained by the high natural durability of this species. On the other hand, scientists discovered that even the most durable timbers would last only a few years if placed in a warm, damp and badly-ventilated space.

Every engineer should know the principal causes of deterioration of wood in service. These are fingi, termites and other insects, mechanical failure and fire. Ancient Romans suggested that some chemicals should be applied to increase the resistance of timber to such agents of destruction. Such chemicals were called preservatives. One or two substances were used for this purpose in Roman times. But the wide use of wood preservatives is a development of the last hundred years.

In practice, preservatives are usually applied to nondurable timbers. The treated wood is sufficiently resistant to the agents of deterioration. Thus, there is a possibility of using a less durable and not so expensive timber instead of durable but more expensive one.

The selection of the most suitable chemical and the method of treatment are of great importance. It is necessary to understand the advantages and disadvantages of using preservatives. No preservative guarantees complete immunity. A preservative suitable in one case may be useless in many others.

General understanding

Read the text attentively and answer the following questions:

1. Is timber an everlasting material?

2. What does the serviceable life of wood depend on?

3. Why did wood in the Egyptian tombs preserve so well?

4. What influences the preservation of wood?

5. What should every engineer know?

6. What did ancient Romans suggest to increase the resistance of timber?

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7. Were wood preservatives widely used in Roman times?

8. What is the purpose of preservative application?

9. What do preservatives make possible?

10. Do all preservatives guarantee complete immunity?

Vocabulary

Exercise 1. Match the English words in A with their Russian equivalents in B.

A 1. destroy 2. ordinary 3. sound 4. preservation 5. last 6. durable 7. apply 8. destruction 9. failure 10. preservative

B 1. сохранение 2. антисептик 3. применять 4. разрушать 5. обычный 6. повреждение 7. здоровый, крепкий 8. сохраняться 9. разрушение 10. прочный

Exercise 2. Find the English equivalents to the following Russian.

постепенно; срок годности; окружающая атмосфера; непрочный; предлагать; химикаты; антисептики; обрабатывать; дорогой (о цене); вместо; подходящий; выбор; полный; случай.

Exercise 3. Choose the words from the text which have the similar meaning.

destruct; working life; solid; strength; resistant; conserve; wet; badly-conditioned; reasons; taint; to use; to raise; fungicidal treatment; non-resistant; merits and demerits.

Exercise 4. Fill in the blanks with the words from the box.

resistance, durability, preservation, species (2), causing, destruction, deterioration, environment, increased, treatment, preservative

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1. Foresters are the key man in ________ of forested lands. 2. Acid rains contribute to the _______ of forests. 3. Wood-destroying fungi affect the mechanical _______ of timber. 4. The two main types of insects ________ the ________ of timber are beetles and termites. 5. Natural timber varies significantly from ________ to _______. 6. The effectiveness of the preservative ________ depends mainly on the amount of preservative that is absorbed by timber and the depth to which it penetrates. 7. The natural durability of wood-based panels can also be ________ by a preservative treatment. 8. The preservatives should be non-toxic to humans and ________. 9. No ________ can guarantee complete protection.