Better Living Through Chemistry (Polyurethane Glue)

I figured out how to get the granite sink level with the base of the new counter top. The method was a variation on a couple of posted comments.

The sink rim thickness varied a bit, say 10%, and it was not exactly flat. I cut out a 1/2 inch wide recess for the rim that was about 1/8 of an inch deeper than required. When I set the sink in place, it was exactly right in a couple of spots, and low in others. I shimmed the corners to be flush with the top, leaving a zero to 1/8 gap between the cutout and the sink.

After shimming, I removed the sink, making sure to keep the shims in the right spot (a little wood glue on hte bottom side of hte shims made them tacky). I put a generous amount of polyurethane glue all around the recess and set the sink back in place and clamped it. As the glue dried, it expanded up to about 4 times its original volume and filled the voids. Now the sink is fully supported and glued solidly in place. The variation is now zero to about 1/16 below the plywood, which is perfect for taking the granite tiles.

I am leaving it clamped over night to make sure everything stays solid. If there are slight positive spots, I will sand them down where the granite overlays.