Rise And Fall Of The ‘King' Of Wood Preservatives

Chromated copper arsenate (CCA) is one of the best inventions in the history of wood preservation, and India is proud to have given the world a product that ruled supreme for over 60 years. This article is a tribute to its inventor, Dr.Sonti Kamesam (1898-1952).After its discovery as ASCU, compounds of chromium, copper and arsenic in various proportions were designated as CCA and became the first runner to impregnate timber and other wood products, especially those intended for outdoor use and in ground contact, in order to protect them from attack by microbes and insects. Like other copper-based wood preservatives, it imparts a greenish tint to treated timber; but this does not adversely affect its texture and grain, writes Satish Kumar.

- Satish Kumar

While wood preservation can be traced as far back as Biblical times, our ancestors relied mostly on naturally durable woods or the use of natural products to enhance durability. It is believed that during the times of Alexander The Great (350 BC), bridges were built using wood soaked in olive oil.

Since olive oil has hardly any toxic components and is water repellent, it helped keep wood dry, an important and non-toxic method for protecting wood against decay. The use of mercuric chloride and arsenic oxides started in the 1500s to control termites.

While the use of mercury was soon discontinued, because of its high toxicity to mammals, the use of arsenic flourished in many formulations. CCA had its birth as ASCU in India, at the Forest Research Institute (FRI) in Dehradun in April 1933.

Although water-based, CCA becomes totally un-leachable after reaction with wood. It offered clean appearance to treated wood and posed no problems in painting or application of any other finish to the treated wood surface.

Besides, it enhanced the dimensional stability of wood, reducing its hygroscopic behavior (Kumar and Jain, 1976) and improved performance against fire (Jain, 1953). None of the earlier water-based formulations possessed such high levels of leach resistance and overall performance against wood-destroying organisms.

India connection

CCA is thus one of the greatest inventions in the history of wood preservation to date, and India is proud to have given the world this formulation which ushered in a new concept of all-round protection of wood almost in any application facing different types of biological as well as terrestrial factors.