First United Methodist Church, Valparaiso, IN
The bain of public concrete labyrinths is not skateboards or roller blades, it is bicycles. The rubber marks left on the concrete are very difficult to remove. Most people don't accept our proposed solution: coiled barbed wire. They seem to think it would detract from the labyrinth.
Zylene will remove rubber marks. However, it also removes the solvent-based sealer. In such case, the treated area needs to be re-sealed.