As many of us have learned, if you have delidded your CPU and used a liquid metal TIM, when you go to change your configuration, the TIM can leave a lot of discoloration. So folks also use liquid metal TIM on to of their integrated heat spreaders as well. And this can lead to issues if you are trying to read the serial number on the CPU. der8auer shows you how to get that nastiness off, if you really need to. 10% hydrochloric acid makes for a good start! Check out the video.