I have actually watched this happen on a motorcycle tank. The gas warms up in the sun and the vapors make their way between the top coat of paint and the primer or metal underneath. The gas cap seal prevents the vapors from escaping over and past the top of the paint. Eventually the paint gets hard enough that this wont happen but I think it takes months not weeks for paint to get hard enough. I almost cried to when I saw this happen :-(
Last edited by mendonjo; 01/06/2013 9:40 AM.
