TWO decades ago when the Shanghai J.W. Cleaning Management Co Ltd was set up to provide services cleaning the exteriors of highrises, the price charges per square metre was between 3 to 5 yuan. These days, despite the increase in the number of high-rise buildings, the price has fallen to less than 1 yuan.

Acid cleaning

Aside from the participations of more cleaning companies, another reason for the lower prices was the reduction of costs due to the use of low-quality detergents containing hydrofluoric acid, which erodes the surface of the buildings.

The chemical is as corrosive as sulphuric acid. The detergent, if it falls onto passers-by or plants on the ground, is said to burn the skin slightly and kill the greenery.

"Usually, they mix 15 per cent acid with water as a cleanser," said Chen Renliang, general manager of the company. "It can quickly remove dirt and stains by eating away a tiny layer of the surface, but the building soon looks dirty again after being cleaned."

The chemical works best on building surfaces made of tile or stone.

Before 1995, the cleaning companies needed permits to purchase a limited amount of the acid. But the requirement for such permits was later abolished. Since then, the acid started to be widely used.

"Nevertheless, the stains forming on the buildings are getting increasingly difficult to remove, so the companies have to keep raising the proportion of acid in the detergent year by year," Chen said.

Those in the property management departments of the architects feel they have been blinded by a cheap trick.

"We pay 8,900 yuan (US$1,000) for every cleaning and I have no idea what cleaner they use," said a women surnamed Huang, working for the property management department of an office building on Huaihai Zhonglu.

Chaotic market

Shanghai has become very proud of its high-rise cityscape, with more than 4,000 lofty buildings, considering it a demonstration of its modernity. Among these structures, about 700 are office buildings and the rest are residential.

Only the office buildings are regularly cleaned. Each is normally cleaned three times a year.

According to one insider, the total public area in Shanghai that needs to be regularly cleaned, including highrises, elevated highways, metro trains and airports, covers more than 500 million square metres.

The city has over 150 legally operating cleaning companies, but there are also many "guerrilla teams", providing such services at half the price of their legal competitors, using inferior detergent.

"They can only be contacted by cell phones and cannot be found again afterwards. Nevertheless, the property management departments prefer cheaper ones because the saving is a good thing for them to show off in front of their bosses," Chen said.

It's a "chaotic" market, according to Chen, which no regulations or adequate licensing adequately covers.

Few factories produce the specific detergent required for the work, so the cleaning companies have to make it up themselves.

The price for one litre of imported detergent suitable for the task is 6 yuan, compared to 3.6 yuan for the domestic product. The corrosive acid mixture, however, costs no more than 0.8 yuan.

"According to the different kinds of staining on various parts of the buildings, we should use different cleaners," said Cai Peigang, a chemist turned detergent maker.

Dirt, smears caused by vehicle exhausts, rust and the rotting of construction materials are among the most commonly seen stains on buildings. Even the rain in Shanghai contains plenty of acid and alkali.

Expensive coating

"The best way to avoid the corrosion is to brush a layer of protective material onto the surfaces, however, few builders have been willing to spend 25 yuan per square metre to solve the problem this way," Cai said.

One example, which both Chen and Cai mentioned, was one of the city's key attractions - the Oriental Pearl Television Tower.

Although the "pearls" shine splendidly at night, the concrete supporting columns have been looking increasingly dark and yellowish recently.

Chen said this was due to the inferior protective coating they had been painted with. The columns are not cleaned unless the city hosts big international conferences, such as the 2001 APEC meeting. His company was once in charge of the tower's cleaning work.

Because of the special shape of the tower, it is hard to clean the lower half, although parts of the spheres and the upper parts were regularly cleaned.

Luckily, protective coating materials are being considered for some of the heritage buildings on the Bund, regardless of the costs.

Dangerous work

It is a common practice in other regions, such as Hong Kong, for new high-rised buildings to be equipped with special supports for cleaning work, set on top of the building from the beginning. This requirement has even been written into the law.

However, on the Chinese mainland, less attention has been paid to this point.

"The apparatus costs several million yuan and most properties have been unwilling to spend such sums on this, so we have to use our own simple facilities, temporarily attached to the outside of the buildings," Chen said.

As well as using inferior detergents, the "guerrilla cleaning teams" were not well trained and the workers didn't have any insurance, which also gave them a competitive advantage over lawfully operating companies, according to Chen. "It also sometimes leads to accidents."

The latest death of a cleaning worker, in a fall from a building, took place on Haining Lu in the Hongkou District on February 2, as reported in the Xinmin Evening News.