There is an old 5 gal.can about 1/2 full of a silver substance that the former owner left outside my shed but the label is all coated which, I wonder if it's what is on the roof now. I am a 70 year old widow who bought the mobile home last August and a former roofing inspector mentioned last year that the roof should be sealed at the seams. I haven't been able to find anyone in Sonora, CA yet who has time or available ones who have given me a price less than $800. just to have it sealed at the seams. I don't know what the cost should be for a job like that either.