Marble Grinding & Polishing
While the finished look and feel of marble installations is generally polished and smooth with a reflective surface, it takes numerous steps to get the natural stone to that point.
When it is excavated from the Earth it is rough and jagged, and while it can be shaped into tiles and slabs, manual labor is the only way for the stone to achieve its reflective polished finish.
There are two types of grinding done with marble: surface and edge. With the former, the objective is to take the overall surface area and grind down any imperfections, or work your way down from a rough finish to a finer, more polished finish. Use a large floor-grinder, which is held with both hands and guided by the user as he walks behind the machine, for large-scale floor projects. Diamond or carbide pads are used for general grinding or polishing purposes, while grinding machines with diamond-tipped teeth are used for areas where high spots or excessively rough sections of stone must be worked down until they are level with the rest of the floor.
Edge grinding creates a rounded edge at a visible termination point, such as the edge of a countertop or bookshelf. This is known as a bullnose edge. A hand-held grinding tool with diamond or carbide pads and discs works best for this. Routers create a tooled edge using a gauge and guide, while hand-held grinders or rotating tools allow you to create custom edges.
Several steps are involved in polishing the marble. The initial grinding of either the surface or the edge is done with the roughest pads and discs, which are useful for grinding down through the natural stone. However, polishing is achieved by multiple passes using increasingly finer discs and pads, with each subsequent pass increasing the degree of smoothness as another fine layer is ground off the surface. The smoother the finish, the higher the level of polish. You can choose your degree of polishing, from the “honed” look of slightly-smoothed stone to the polished marble finish with the reflective power of a mirror. Special wipe-on conditioners and sealers are available to enhance the sheen of the stone when finished.
Wet Versus Dry
There are two grinding methods: wet and dry. Which one you choose will be determined by the type of installation and whether you are performing the grinding and polishing outdoors or indoors. The wet method relies upon machines that use either oil or water in conjunction with the grinder; the by-product of wet grinding is liquid sludge. The dry method, on the other hand, creates excessive amounts of stone dust. Dry machines often come with a vacuum attachment to help minimize the dust. There is no real difference in the finishes created by the two methods. In general, liquid polishers are used for large-scale floor polishing, while dry polishers are usually hand-held and used in finishing edges and small-scale projects such as countertops.