In todays post we will be discussing the science of polishing.
Grit levels, 120 for example, are the number of scratches per inch that a diamond polishing pad or stone will create. A 120 grit pad will produce 120 scratches per inch in the floor. That said, it works just like sanding wood. Installers will start with a rough grit, typically 24-50 grit level and work finer and finer to create a polished finish. The idea, being the more scratches per inch the more "closed" a surface becomes. See attached/included diagram.
With epoxy terrazzo the "Industry Standard" is a 120 grit polish with a generic topical sealer.
The samples you get from Terrazzo & Marble Supply Companies are polished to 200 grit (Unless, our clients instruct us to do otherwise). We like to take the sample one additional level to further saturate color and produce a more aesthetically pleasing sample.
As with polishing marble or granite, we have the capability to produce a high polish floor up to 3000 grit. This is a very high polish and it will look just like a piece of polished marble or granite.
To get to 3000 grit, the polishing process would go like this:
24 (Rough Grind to initially cut the floor to the divider strip height)
80 (Removes heavier scratches from previous step aggressive diamonds)
Grout Coat (to fill any voids and fissures)
120 (Recognized by NTMA as the Standard Finish Level and will require a topical sealer)
220 (Terrazzo & Marble’s Standard Finish requires topical sealer)
400 (Requires topical sealer)
800 (First Level considered “High Polish”, polish levels from this point on do not require a topical sealer but will require a impregnating sealer to seal any porous chips, meets SCOF for accessible routes)
1500 (Increases reflectivity and color saturation)
3000 (Increases reflectivity and color saturation)
Note the numbers and grit levels can very slightly, for example: 200 instead of 220. This is referred to the mesh size. To see the difference between a 200 and 220 mesh size you’d need a microscope. There are many different companies that produce polishing products so there are all different types of polishing pads and stones. Nonetheless, 200 or 220 will yield the same result.
Why would we want to polish higher? It produces more color saturation, higher reflectivity, is more scuff resistant, eliminates the need for a topical sealer and lowers annual maintenance costs. Plus, it looks nice. However, it does add cost. Each grit level requires the installer to polish over the entire floor so it's more labor. Typically adds around $3 per SF (Over the Standard Finish) depending on the desired finish level of polish.
Hope this is helpful. Let me know if you have any questions. Thanks!