With the help of students from Trinity College, Colac, Friends of the Earth conducted a Citizen Science Experiment investigating the effect that a number of popular Australian sunscreens have on the coating of Colorbond steel and on varnished timber. The experiment replicated a 2008 study which found that nanoparticles of anatase titanium dioxide in sunscreen were reacting with sunlight and aggressively producing free radicals which broke down the coating on Colorbond steel 100 times faster than would normally occur. Our experiment found that several popular sunscreens caused serious damage to wood varnish.