The painting isn't finished, obviously, but I went ahead and played with the aging techniques I was thinking about. I remember an interesting lecture on painting restoration, and that varnish, over time, cracks and yellows, giving old paintings that warm glow and distinct pattern. So in Photoshop, I added a light golden yellow layer on "multiply." You can use a photo filter (warm) as well. For the cracking, I hand drew squiggly lines, mostly vertically, in the pattern I saw on a detail of a Vermeer. There are different patterns of cracking depending on the varnish used, but this seemed like the easiest to reproduce. I made this texture as a repeatable tile, and changed the color to a very light brown (hue/saturation - colorize). When I applied it to my painting, I shrunk the tile down very small and covered the whole painting with pasted versions that I had flipped horizontally and vertically. Finally, I changed the layer to "multiply" and reduced the opacity to about 35%. Other ideas I might try...adding a very subtle canvas texture over the whole thing.
