More Leveling

The most time consuming aspect of making our countertops is making sure they are flat and level.  This wasn't a problem I had with the samples I made because the samples were so small that imperfections in flatness or level were not detectible.  Imperfections in flatness and level do show up on the larger surface areas, so this is something I've had to figure out.

At first, I tried to eye-ball the level, that didn't work out.  The human eye can only see so much at once.  The brain fills in details that just aren't there and something that looks level isn't.  

The next method I tried was to use my T-square to find all the valleys, mark them then grind down to them.  The problem with this method is that not all valleys are the same height, nor are they all level.

At present, I'm finding the highest spot, marking it, and grinding it down.  This seems to be the most accurate method.  It's also very time consuming.  I'm using my longest level, marking the high spots on the X-axis, and marking the high spots on the Y-axis.  The high spots are simply the parts of the countertop that touch the bottom of the level.  I'm shining a bright light across the counter top on the side opposite to where I am so that as I look under the level I'll see the light anywhere light passes under it.  I'm also using my putty knifes to lift the low end of the level to make the level . . . well . . . level.  I'm marking all the places the light does not pass under the level using the level like a ruler.

Notice the hash-marks I've drawn on the countertop in the photo above.  the places where the hash-marks intersect are the only places I grind down.  Eventually, when the counter is flat and level, no matter where I put the level, the entire level will touch the surface of the counter top and no light will pass under it.

At the moment, there is a 2 mm difference between the highest and lowest points on the kitchen island counter top which are just over 2-feet away from each other.  Grinding down these peaks requires a very light touch.  I've already turned a couple peaks into new valleys so I've put the 15-Amp Makita high-speed grinder away and switched to my variable speed polisher with the large 7-inch grinding wheel on a low speed.