If you were OUTDOORS....painting non-vinyl siding that had been powerwashed, I would tell you that grain shadow is pretty normal. But indoors??? So, about primers, the most robust are meant to 1) provide a surface for the finish paint to grip and 2) seal in any things that might bleed through, e.g. Water stains, rust, whatever. And as Joe said, for MY money, anything that claims to both paint and prime are crap.....but they will make the do it yourself er happy.....if they work. So I am NOT a professional painter...but if I put ONE coat on a wall.....and see dark and light areas, I am backing up and using a primer over everything to eplevel out the playing field. So, required war story, in. My sons house which had blue board and plaster skim coat, prior owner moved an outlet in the bath and just put a patch with joint compound n the left over space....and then put wallpaper over it....which we didn't see upon inspection ....or three years later....but now four years later, we can see the patch....right through the dark blue vinyl wallpaper...coming thorough as an area that was not sealed over. Ron
