My boyfriend and I decided to have an impromptu BBQ on the concrete front patio. That was the 1st bad idea.
Since we were in a rush to go to the airport, we decided to throw water on the coals to cool them down. Dust, soot and random other black things landed on our patio. The patio now has a huge dark stain which we've tried to wash and scrub to no avail.
How do we get rid of the stain? Thank you for your help!