That looks like you had your laptop in front of a candle, and you burned it.
Happened to my friend once. If that's the case you essentially burned the aluminum and the best way is to get a new cover which is $50
My guess is that it's finger tip dirt from being picked up. I'd try either a little dab of dish soap (Dawn, etc.) on a damp cloth (rinse well afterward) or the rubbing alcohol. Rubbing alcohol would probably be the easier of the two as it doesn't require rinsing.
Nope definitely not a candle. This laptop only goes to 3 places: My desk, my suitcase, my office. No lighter / candle anywhere in sight and I'm always next to my Mac.
Is alcohol safe to use on these cases?
I believe that Rubbing Alcohol is safe to use on the aluminum of Macs. Use it sparingly on a COLD Mac away from fire or pilot lights, etc. in a ventilated area (it's flammable) and DO NOT use it on the screen. Rubbing alcohol evaporates quickly so it shouldn't leave any kind of residue behind. Let us know how this turns out for you and what you end up using.
I'll use rubbing alcohol I'll just have to try it tomorrow morning since i'm on my mac now and i'll be on it till 10pm. wish me luck i'm nervous as hell now with using alcohol. also it's on the outer case not using it anywhere else.
Is alcohol safe to use on these cases?
I believe that Rubbing Alcohol is safe to use on the aluminum of Macs. Use it sparingly on a COLD Mac away from fire or pilot lights, etc. in a ventilated area (it's flammable) and DO NOT use it on the screen. Rubbing alcohol evaporates quickly so it shouldn't leave any kind of residue behind. Let us know how this turns out for you and what you end up using.
It's aluminum, I don't see why it wouldn't be safe to use rubbing alcohol on it.
Why are we not supposed to use alcohol on the screen? it's a layer of glass over the LCD panel isn't it? I honestly don't think that the glass is some super sensitive/special "apple" glass that can only be treated with special apple certified cleaning solution. Of course, I'm open to any evidence that suggests otherwise, thanks!