The angel atop Victoria Memorial Hall will start twirling again in May.
Memorial director Chittaranjan Panda announced on Thursday that the team working on the project had made the angel rotate, about 10 degrees, after a gap of seven years.
'It will take another month-and-a-half to make the angel rotate 360 degrees. We cannot hasten the process, as applying too much pressure could damage the bearings. If they develop a crack, a fortune will have to be spent on replacing them,' said Madhusudan Bhattacharya, former head of the mechanical engineering department, Jadavpur University, and leader of the repair team.
The 4.9-m sculpture, weighing about 3.5 tonnes, had stopped twirling in 1999 after the ball bearings, cast in bronze, got stuck. This happened due to a lightning, which melted the bearings, welding them to the base. The layer of mercury that was used as lightning conductor had solidified and proved useless.
'The angel should soon start twirling again,' said Bhattacharya.
Panda said: 'It was Bhattacharya who had restored motion to the angel when it had stopped rotating in 1985. That was first time the angel stopped twirling since it was installed in 1921. This time, too, he volunteered to repair it.'
A layer of cement and marble dust was obstructing the movement of the ball bearings. 'We had to clean up the cement and dirt that had accumulated, before lubricating the mechanism. Then, with the help of moderate rhythmic torque (clockwise and anti-clockwise pressure with a shaft) we were successful in getting the balls to roll,' Bhattacharya explained.
Environment activist Subhas Dutta had moved a petition before the high court in 2005, stating that the angel was causing structural damage to the monument. Submitting a report of an expert committee, Dutta had observed that it is important for the angel to twirl to avoid pressure on the dome of the Memorial.