Mine got a noticeable buildup on the bottom of the vent cap. I tried all sorts of cleaners to no avail. Recently, I was looking at pics of shiny bronzes, with their shiny to vents, and I got determined. I got a magic eraser, and just started rubbing on one tile. Finally, it came clean! I repeated the process, tile to tile, until the eraser was gone. There were still dirty tiles, but I noticed in my sink, when I was rinsing the eraser, I had a two sided kitchen sponge, regular and a bit more abrasive. Well, I hit it with the abrasive side, and off comes the residue! I moved to little boy, and cleaned the whole top vent in the time it took to do four tiles with the eraser.
I'm gonna try some of this mix, as I'm not gonna let this build up happen again, I love the look of shiny bronze!!
Robert