I need to discover how to polish marble. There is some marble flooring in my house that has seen better days. The scratches aren’t too deep, but they look bad. I also had to cut a piece of marble and now have an ugly, dull stone edge that needs to look like the high-gloss polished finish on the top. What’s the secret? Do I need all sorts of expensive equipment? Do I need to use water? —Paul H., Santa Barbara, Calif.
You’re in luck. The great news is that you’ll be able to get very nearly professional results in short order. It may take a little practice, but I think you’ll be amazed at how easy it is to take a dull stone edge and give it a highly polished surface that broadcasts the natural beauty of the stone.
You don’t need thousands of dollars of expensive equipment to polish marble. It’s quite possible that the tools you need to achieve very good results are already in your garage or workshop. At the bare minimum, you need a regular drill that has a variable-speed motor. If you have access to a stone grinder, that’s all the better.
There are two basic ways to polish marble and other stones: the dry method and the wet method. It’s hard to believe, but dry polishing works very well. This method creates a fine dust, so you need to work in a place where dust won’t ruin things. When dry-polishing, you need to wear eye and breathing protection. It’s not a good idea to ingest stone dust into your lungs, especially stone dust that contains silica.
Using special silicon-carbide sandpaper made for stone polishing, you can cut away successive ultra-fine layers of the stone until you have a high-gloss finish. You can buy sandpaper that attaches with adhesive or hook-and-loop technology to a flexible round sanding pad. These pads attach to a regular drill or to a special mounting base that connects to a stone grinder.
The polishing process starts with coarse-grit sandpaper that has a low number, such as 24 or maybe 60 grit. As the grit number gets larger, the size of the silicon-carbide particles gets smaller. Grit sizes march through the double digits, triple digits and beyond.You’ll be using 120, 220, 400, 500, 600 and more than 1,000 grit.
With the coarse-grit paper, you cut away a fine layer of stone to remove the scratches or saw-blade marks. It’s critical that you cut away all grooves, leaving a surface that may be rough, but all in the same plane. If you leave small grooves, tinier than the thickness of a piece of hair, you will see them as you start to achieve a high polish.
When you use the tools, you need to keep them moving. The drill or grinder will be spinning, so don’t keep it in one spot on the stone. You must slide it constantly across the surface of the stone so the sandpaper doesn’t cut a circular groove. Moderate pressure is all you need. Let the sandpaper do the work for you.
It’s best to use many different grits of sandpaper as you start to achieve the polish. You may start with 24 grit, then use 60, 120, 220, 320, 400, 500, 600 and then 1,000. If you skip a grit, you may end up with tiny scratch lines that show through the polish.
You can also use dry diamond polishing pads in the same manner. They also come in different grits, going as fine as 3,000.
It’s best to test your skills on a scrap piece of marble first. Try to get a piece that matches your floor marble so that you can see what it’s like. Use some regular sand to scratch the scrap piece and then start to see whether you can polish these scratches out like a pro. Once you have achieved success with the scrap piece, advance to your floor and to the cut edge.
Tim Carter is a columnist for Tribune Media Services. He can be contacted through his Web site, askthebuilder.com.