Lines in wood

[tchewtch]

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.

[Bizman62]

Don't worry, they're solid wood. I've got similar streaks on my builds which I've made from scratch, both "tonewood" alder and roasted sauna bench alder. I don't know if it's because of humidity or UV light that they pop out from seemingly uniform wood but they definitely are a change in colour, not a crack.

What causes them can be a damage in the wood, though. The tree may have bent so heavily that it cracks, and the tree then heals the cracks with new cells that aren't aligned similarly to the "old" wood. Inner scar tissue, in a way. I may be wrong here but doesn't that sound logical?

[mistermikev]

I would agree w @Bizman62 that it's nothing to worry about.  seen lots of strange things in wood over the years... think it was scottr here that had some sort of 'chain link fence' pattern in ash... I've since had a piece with that myself (man that was one looong fence and one biiiig tree!).  This actually looks like some sort of fleck or grain... but could just as easily be the edge of a split.  I have a split like this in my current ash tele build but it probably only goes in 1/4".  clearly doesn't go thru the piece as theirs a ctrl cavity right on the other side of it and it doesn't go thru.  wood must have dried and split... and this was just the edge of it.  Just filled it with dust and ca and one we go.