I'm in the process of improving the heat sinking of the pill on my flashlight. I read aluminum oxide has low thermal conduction and I was thinking of sanding the bottom of the LED heastink a bit. I noticed that when I'm making continuity test with a multimeter I have problems making connection with both probes touching the bottom of the heatsink. Is there a clear coat on the heatsink so it doesn't form an electrical path to the pill? Or is it aluminum oxide?