I've built a few coops before so I know roofing basics. The question is - I work at a news paper company and the method of printing is plates. Theres a chance I may be able to get some for free, would these make for a good roof? They would be used and have ink on them, they are aluminum sheets about 3'x2'. The ink should wash off with some scrubbing, but they also have a coating of something white, which I do not know what is. Any thoughts?