11.   The workers have been hanging from suspended cables inside the dome to clean its surface and patch up cracks, in a project begun earlier this year.

12.   They clean tooth surfaces as you chew.

13.   This will clean the surface and dull the finish, which can be restored by buffing with a clean cloth.

14.   Turn out onto a large tray or clean work surface and break up any lumps with wet fingers.

15.   A method has not been chosen to clean the surface, dotted with black crust and soot from pollution, Ms. Papanika added.

16.   But tests have shown that they are not effective in cleaning tooth surfaces.

17.   No method has been chosen to clean the surface, which is dotted with black crust and soot from pollution, Papanika said.

18.   The final year of the project will be spent cleaning the surface, which has suffered from centuries of erosion and pollution damage.

19.   They included techniques for recycling rubber, using alternative energy sources and cleaning polluted surfaces with biodegradable agents.