I'm building up a partscaster from an unfinished body. The body sat around for a couple of months in its bare state before I put an acrylic seal coat on it. Before I sealed it, a few dark lines appeared, which I thought may be hairline cracks. They could not, however, be detected by scraping my nail across. They also do not follow the grain. Since sealing it (not yet sanded) I've noticed that more lines have appeared. Does anybody know what causes these lines? Is it humidity related? Is it a problem. They will eventually be painted over, so if it's just a visual thing I'm OK.
Thanks, Dave.
