Polishing concrete is a process that has been around since Roman times. These days, thanks to modern technology, the process is a bit simpler. In order to polish any material, you have to use the process of lapping--continuously rubbing with a progressively fine abrasive to achieve a smooth surface. There are many types of polishers that can be used to polish concrete, including hand-held angle grinders, Terrazzo-type floor polishers, radial-arm polishers, and bridge polishers. These machines will use three types of heads: flat plate heads, satellite or planetary heads, or oscillating segment heads. The challenge to polishing concrete comes in the attempt to polish the cement that holds the aggregate together. The micropores in the cement, caused by the excess water needed to make the concrete workable, create an eggshell or orange-peel effect on the polished surface. Therefore, to keep this problem to a minimum, an extremely dense surface must be achieved for polishing to be effective.