Department admits its use of a hi-tech material to fight fungus was a mistake State-of-the-art technology used to protect timber columns on Lantau's Wisdom Path has proved useless against Mother Nature, a senior government official admitted yesterday. Deputy director of Architectural Services Marigold Lau Lai Siu-wan acknowledged that officials had 'made a mistake' by spending HK$200,000 to use a nanotechnology coating - a material developed at the atomic or molecular level - to protect the wood. Remedial work will cost another HK$410,000. The nano titanium oxide protective coating contained particles that were too small to stay on the tree bark, she explained. The coating was applied based on the results of a laboratory test. 'No one understands how to protect wood in the outdoors,' Mrs Lau told a conference on the issue at the University of Hong Kong. 'We are learning through mistakes.' The South China Morning Post reported in September that some of the 38 timber columns, which stand between eight and 10 metres and have calligraphy by sinologist scholar Jao Tsung-I on one side, were found to be sprouting fungus and mould. The path, which is an outdoor tourist attraction near Po Lin Monastery, was opened in May last year. The coating, which is water-soluble, also made it almost impossible to protect the tree bark from the city's humid weather. The wood would have been easier to preserve had the bark been removed, but it was kept for aesthetic purposes, Mrs Lau said. Because the side inscribed with calligraphy was shaved and peeled, it had suffered minimal damage. To solve the problem, the department began applying silicon coating - an accepted method of protecting wood from water, germs and fungus - on the columns at the beginning of this month. The coating is expected to last about a year. The project will finish by December. Tree expert Jim Chi-yung, of the University of Hong Kong, who was consulted on the project, said it was unavoidable that the columns would face humidity, fungus and germs. 'The bark or the outer surface would be corroded easily because it was not protected well by tree resin,' he said. Professor Jao, 90, made a rare public appearance yesterday to defend the government. '[The columns] are put outdoors so this [mould and fungus] is not a problem as this is part of nature,' the University of Hong Kong honorary professor said. But he was glad the government was using an improved method to protect the columns. 'I hope they can be kept for 100 years,' he said. Legislator Choy So-yuk said yesterday the government seemed to be 'too careless' in using a laboratory test to decide which method would be best for protecting the columns. 'This is a waste of public money for the sake of trying out high technology,' she said. 'But then if they never tried, we might have also complained that they never tried something new.'