When visiting Corona Heights Park with a friend, one of the residents wondered out loud to me why it was that no one removes the graffiti from the big rocks. When I got home, I was surprised at the answers I found online concerning removing graffiti from natural stone in SF.
Geological data available about natural areas in San Francisco are available online. Sure enough, when I checked the SF Natural Places site, I found that Corona Heights Park has a lot of “Graywacke” sandstone in it. This means that it is a kind of soft stone similar to limestone and marble.
Unfortunately, this means that removing graffiti from these surfaces can often lead to damaging them permanently. Of course, the Federal government and the Natural Preservation Society have worked overtime on this type of graffiti abatement issue. Chances are the people in charge of graffiti on the big rocks in Corona Heights Park are simply waiting for better solutions to come along.
In the meantime, it looks like we’re stuck with whatever juvenile graffiti gets left behind. If you see someone defacing the park, try and educate the individual that it is a historic place to and ask them to stop immediately.
If you do not feel you can be successful at preventing them from placing graffiti on the big rocks in the park, walk away and call 911.