We use 2 component lacquers (catalyst added) that have been tested for extreme weather applications. 90 days. 2016 hours. Heat. Heat plus UV. Then Moisture and back to Heat again. Acrylic for dark colours and Polyurethane for whites, etc. Fibreglass Exterior Doors is our main biz. We have finished more than a thousand fibreglass doors over the past 10 years.