I wanted to mention some things about the tools that I used, since a lot of people are looking for some direction on what grinder to use for this wet grinding and where to get diamond grinding pads.
First, I used a Secco Wet Grinder (picture below) that I ordered from BargainBlade.com. It’s probably a lower-end grinder since it’s only about $160, but it’s a variable speed grinder with a built-in water feed and GFI. It worked just find for my hours and hours of grinding and the only issue I had with it was the switch lock mechanism seemed to get a little gunked up with grinding dust and the switch wouldn’t say in the “on” position until I cleaned it out. I had to fuss with the switch a few times during the project and that was it.
Diamond grinding/polishing pads are expensive and generally seem to run about $20 per pad. Just for a basic matte finish, you probably need four or five different grits so you’re already over $100 just in grinding pads. If you order a Secco wet grinder, you can buy a kit which comes with seven different 4″ pads of varying grits for an additional $30 or so and it’s probably worth it to buy the kit if you’re buying a grinder. (I’ve since discovered that toolocity.com has some diamond pads for very reasonable prices. I’ve not ordered from them, but I’d consider it if I need some more pads in the future.)
For my project, I also bought the ground+matte finishing kit from Cheng Concrete. I figured since it was the first time I made a concrete countertop, I’d buy the finishing kit from the experts. The grinding pads are 5″, so they are larger and theoretically should speed up the grinding/polishing process. I found the pads wobbly, whether from the polishing pad holder or the pads themselves, I wasn’t sure, but it wasn’t as smooth a grind as the 4″ pads which cost me all of 30 extra dollars for seven different pad grits. Still, the coarse 5″ pad was nice to have for the grinding portion, so I have mixed feelings about the finishing kit.
To me, the best things about the finishing kit were the polishing pad and the wax. It made things much easier to already have the polishing supplies on hand. If I did a project like this again, though, I’d probably pick and choose individual items, since Cheng Concrete seems to charge a bit of a premium for their supplies and I wasn’t overly impressed with the diamond pads.