Mark pulls out the big guns, reserved only for very stubborn dirt. You need to move quick though, or else you will end up dissolving the tile. And that would be kind of like burning down the house to get rid of the mice. Simply put: Overkill.
If you would like to print any of the pictures on this blog I would be happy to send you a full rez edited image file for your use. Please click on the picture you would like and copy the address at the top of your browser, then just send the link to the3dmodeler (at) dejazzd (dot) com and I will try to get you your image file ASAP!