If your fiberglass columns haven’t been painted yet and are dirty use water to wash away the dirt and soapy water for tougher stains. If it’s a scuff mark from a forklift or something similar use a high grit sandpaper. If it is just dust use a tack cloth. You can read more about prepping a fiberglass column in our painting fiberglass columns instructions. If the column has been painted follow the paint manufacturer’s instructions for how to clean.