They way we tested sunscreen was by applying different types of sunscreen to separate sections of the sunprint (cyanotype) paper, expose it to direct sunlight for 45 minutes, then compare the color changes of the paper to see which areas received the most UV radiation, showing the effectiveness of the sunscreen in those areas. The areas with less color change will have been better protected by the sunscreen.Â
We also had to cover the paper with Saran wrap and apply the sunscreen on that so that we could see the changes in the paper color.