Creosote
Creosote was the widely used wood preservative in the past. Even 100 years after application creosote oil is found to be an excellent wood preservative.
Coal Tar Creosote
The most common type of creosote is from coal tar creosote. It is distilled from industrial grades of coal tar. Wood creosote has an entirely different chemical make up to coal tar creosote, and is created by the burning of wood.
Both coal tar creosote and wood creosote are thick and oily, and are usually black in colour. Coal tar creosote is the type of creosote used in wood preservative, although the strong and persistent smell makes it unsuitable for internal use.
Creosote Oil
A precursor to creosote was first invented in 1716 by Dr William Crook which was used to protect wood from rot and woodworm. By 1865, plants in America were set up to treat timber for use in the railway industry. Creosote oil is still the preserver of choice for railway sleepers and transmission poles.
Coal tar creosote is usually used for external applications such as railway sleepers, gates and fences. Diluted forms can be used in the garden for fencing and other DIY applications. It is not suitable for use inside the house, due to its strong and persistent smell.
Restricted Use
The European Union has banned the sale of wood treated with creosote and creosote itself can only be sold by professional users. This ban came into effect in 2003 due to fears the carcinogenic properties were greater than previously thought.
Creosote Substitute
Creosote substitutes are usually high pressure chemical wood treatments, as these are suitable for the most common applications of creosote. Creosote is usually used in external applications where risk is high, so a creosote substitute in the form of a chemical wood treatment needs to be effective in these conditions.
Unsuitable for Residential Use
Creosote is rarely used in any residential applications any more, except if a home owner decorates their garden with old railway sleepers. In this instance, care must be taken by the user when handling the sleepers, and frequent contact with the skin should be avoided.
Chimney Creosote
Chimneys can become built up with wood creosote, as the combustion process of wood leaves behind a thick, black substance. The amount of creosote build up will depend upon the density of smoke and the vapour from the fire. Less smoke results in lower creosote deposits.
Chimney Cleaning
Creosote cleaning is essential, as a build up can result in a serious fire. Chimneys can be cleaned by professional chimney sweeps, although it is possible for cleaning creosote to be done by the home owner. Stiff wire cleaning brushes can remove the excess creosote from the side of the chimney.
Creosote Remover
Chemical chimney cleaners are also available, although they cannot clean heavy deposits of creosote and this must be removed with a brush. Creosote remover usually contains sodium chloride or copper sulphate. Copper sulphate creosote remover coats the soot in the chimney and allows the creosote to burn away at a lower temperature than normally required.
Creosote remover containing sodium chloride works by forming a weak acid which dissolves the creosote. The sodium chloride combines with water released from a fire to form the acid. It is corrosive to metal, and alternative methods of creosote cleaning should be used in metal chimneys.
Creosote removers are most effective if used with a new chimney, or after a chimney has been cleaned with a brush. This prevents a further build up of creosote. However, it is important to use the creosote remover as directed or they can cause chemical fires which could damage the chimney being cleaned.