group-icon
Civil Engineering Questions
Question and answers for technical problems related to civil engineering subjects, jobs, courses and more
90 Members
Join this group to post and comment.
Ali Hamza
Ali Hamza
Mechanical
16 Jan 2019

What are different methods of preservation of Timber??

Methods of Preservation of Timber :

Charring:

 Lower ends of the posts that are to be embedded in ground arc generally charred with a view to prevent dry rot and attack of worms. It is done by quenching the ends of posts in water after they are charred on wood fire to a depth of 1.5 cm.

Tarring:

It consists in coating with tar or tar mixed with pitch. 

Embedded portions of timber fence posts, ends of door and window frames, battens and beams built in wall are usually tarred. Tarring is not done in case of those portions of structural members that are open to view, because of unsightly black colour.

Painting:

 Paint when applied to timber acts not only as a good preservative but also it enhances the appearance of the surface so treated. Only well seasoned timber should be painted as otherwise the moisture entrapped in the timber, because of the closing of timber pores by paint, would cause decay. Paint, however, protects seasoned timber against moisture thereby prolonging its life.

Creosoting:

 Creosote oil is a dark brown thick oily liquid. Thoroughlyseasoned timber dried for 24 hours before its treatment is placed in an  airtight chamber. After the air has been exhausted from this chamber  the creosote oil is then pumped in at a pressure of 9 kg/cm2 at a  temperatup of 50°C so long as the timber is not fully saturated with oil.  

The oil preserves the timber from rot and from the attacks of white ant. It is used in case of railway sleepers, piles and transmission poles.  Undesirable colour and smell, inability to take paint well and the  tendency to stain plaster limit its use. 

Wolman salt:

This salt consists of creosote and sodium flouride and issoluble in water. It is odourless and leaves no stain on wood. After  treatment timber could be painted or varnished. These salts destroy  many kinds of fungi that cause timber to rot. This renders the timber  extremely fire resistant too.Treatment of timber with zinc chloride,  sodium flouride, magnesium, silico flouride or copper sulphate renders  the timber immune from the attacks of fungi. The timber so treated is  capable of being painted on drying.