Painted metal roofs are cheap, convenient, and usually very durable. But over the past two years, a rash of accelerated ageing has blighted pre-painted steel roofing in Australia. And intriguingly the ageing—which affects the coating—seems to be localized to small patches, taking on the form of fingerprints, handprints and even footprints.
The culprit it seems is sunscreen that is spilt or otherwise transferred to the roofing by construction workers during installation. And not any old sunscreen—this would appear to be a uniquely nano phenomenon. But I get ahead of myself… Read the rest of this entry »