CURING, GRINDING AND POLISHING. As soon as the laying is completed, the floor should be covered either with damp Hessian or cloth. Precautions should be taken to prevent the floor from being subjected to extremes of temperature. The flooring should be maintained in a damp condition until ready for polishing. About 36 hours after the top layer is laid, the surface should be watered and ground evenly with a machine fitted with special rapid cutting grit blocks of coarse grade (No.24 to 60), till the marble chips are evenly exposed and the floor is smooth. After the first grinding, the surface should be thoroughly washed to remove all grinding mud and covered with a grout of cement and colouring matter in the same mix proportion as the topping, in order to fill any pin-holes that may appear. The surface is allowe3d to cure for 5 to 7 days by suitable means such as covering with damp Hessian or ponding water, precautions being taken to prevent the surface being subjected to extremes of temperature. The surface is then ground with a machine fitted with fine grade grit blocks (No.220 to 350) to get even and smooth surface with a minimum of pinholes. The finished surface should show the marble chips evenly exposed. Where the use of machine for polishing is not feasible or possible, rubbing and polishing can be done by hand, in the same manner as specified for machine polishing, except that carborandum stone of coarse grade ( No. 24 to 60) should be used for the first rubbing, stone of medium grade (No.80 to 100) for the second rubbing, and stone of fine grade (No.120 to 150) for final rubbing and polishing. After the final polish, either by machine or by hand, oxalic acid should be dusted over the surface at the rate of 33 Gms per Smt., sprinkled with water and rubbed hard with a pad of woolen rag. The following day, the floor should be wiped with a moist rag and dried with a soft cloth and finished clean.
