So I'm scrubbing away at the bottom of my CPU cooler with some Q-Tips and isopropyl alcohol. And the Q-Tips keep coming up with some black stuff. I don't see the source of it anywhere on the heatsink. I thought isopropyl alcohol was supposed to be relatively safe. Is it reacting with the copper/residual thermal paste somehow? No matter how hard I scrub, I keep coming with more of the black stuff
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