How can i clean my ceramic straightener?

i have a remington wet 2 straight straightener, and the plates have gone brown, its residue sort of i think, but its just like the plates have gone brown in some places, but i cant get it off. ive used a wet cloth when it was cold, and whenit was warm, and ive used windex, and rubbing achohol, but none of them work. the straightener still works, ok but i think it would work better if it was clean. is there anyhing i can do?How can i clean my ceramic straightener?
i know i prob wrong but i used a butter knife to do mine!!! i couldnt find anything it do it with.it was only on the edges anyway and its a blunt knife so woudlnt scratch but i dont suggest it on the plate.in future tho when you are straightening your hair if you see any residue on them wipe it off as you go along then you wont get the build upHow can i clean my ceramic straightener?
try 409