What is polishing?
Polishing is smoothing a surface in steps with progressively finer abrasives until it reflects light. The difference from grinding is not the tooling but the objective: grinding aims at flatness, polishing at gloss.
Technically this is what happens: every abrasive step leaves scratches. By working each time with a finer grit, the scratches from the previous step are removed and replaced with smaller ones. Once the scratches are smaller than the wavelength of light, the surface reads as reflective.
Where it is used
- Natural stone. Granite, marble and limestone are polished for floors, worktops, sills and cladding. A polished stone looks darker and deeper in colour than the same stone honed or bush-hammered.
- Terrazzo. Here polishing is not a finish but the essence of the process: grinding down the cast mass is what brings the aggregate into the surface plane.
- Polished concrete. A concrete floor ground through successive grit steps and densified with a chemical hardener. It produces a wear-resistant, dust-free floor with no coating that can delaminate.
- Metal. Stainless steel handrails, brass and copper ironmongery, aluminium sections.
The grit sequence
Steps are described by a grit number: the higher the number, the finer. A typical run on stone or concrete goes from a coarse diamond grit (around 30 to 50) through intermediate steps to very fine (800 to 3000 and above). Never skip a step. The scratches left by a coarse grit cannot be removed by a much finer one — they only get polished up and therefore stand out more.
Polishing is usually done wet. The water cools, carries away slurry and stops the diamond segments glazing over. Dry polishing is possible with extraction, but needs tooling made for it.
Practical points
- Polished is slippery. A polished stone or concrete floor is treacherous when wet. In wet rooms, entrances and on stairs a honed, ground or brushed finish is safer.
- Marble and limestone are acid sensitive. Lemon juice, vinegar, wine and acidic cleaners attack the gloss immediately. Sealing helps but is no guarantee.
- Repair is possible. A dulled or scratched polished floor can be brought back by repeating only the final grit steps — considerably cheaper than replacement.
- Maintenance. Use pH-neutral cleaners and no abrasive products. Grit tracked in underfoot is the main enemy: good entrance matting extends the life of a polished floor substantially.
Related terms
- Stone finishing
- Stone maintenance
- Terrazzo
- Granite
- Concrete floor
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