Hello, A retailer that recommends my services has asked me go to a customer that has a pergola floor. He is concerned with the floor picking up the black rubber from his slippers in the main walkway which is leaving a slightly darker area that water based cleaning is not removing. Manufacturer has been out and said no fault on the finish and suggested cleaning with an acetone based cleaner. I get this on carpet and rarely need to use a solvent and have little experience on pergola. Any suggestions(apart from don't touch it). Simon