Just as in life, adding layers makes for a more interesting composition. A white layer made from tires-!-adds a patina of interest. I painted a thinned white layer of oil paint on the piece, then positioned it under my car tire and BOOM!-there ya go! The oil spill occurred in winter, so I'm mimicking the effect. The piece still feels unfinished to me, so I'll see where this layer leads too......
As a working artist/retired art educator, I've always lived the artful life. Let's share!