From the Artist: I've done a bit of craft painting through the years and have learned many fine art techniques by doing craft projects. The rendering of wood in paint is one of them. You could certainly use one of the wood-graining tools, but I've never had much luck with them.
Basically, I undercoat with gesso where necessary, paint a flat coat of whatever color I choose (let's say a light yellow in the case of the top box on the right), put a gloss sealer (your pick, your medium; here I've used craft acrylic paint). I leave it dry (vital that it dries between coats), then I put on a not-too-careful coat of another color (it's a warm brown here). I drag a kitchen sponge through this wet top layer making wood-like streaks, sometimes swirling a bit here and there for the woodgrain. Once dry I put another gloss sealer on top. (Most often, I use something like Folkart's Indoor Outdoor Gloss Varnish.)
Other color options are bright red undercoat with black top coat (shown), greyish undercoat with white top coat... ad infinitum. This is great fun to do on old furniture by the way.
I also do the same thing in oils with my fine art painting (without the use of a sealer between layers or on top, of course). Sometimes I even used my kitchen sponge as a brush on a canvas. Other times, I used a old ratty hardware store bristle brush to make the sqraffito lines in the wet paint, then a soft sable or synthetic to put in darker grain lines or knots in the wood, but I'm using the same technique. Once grain lines are established and dried, I will sometimes add more color in glazes. The options are wide open.
Basically, I undercoat with gesso where necessary, paint a flat coat of whatever color I choose (let's say a light yellow in the case of the top box on the right), put a gloss sealer (your pick, your medium; here I've used craft acrylic paint). I leave it dry (vital that it dries between coats), then I put on a not-too-careful coat of another color (it's a warm brown here). I drag a kitchen sponge through this wet top layer making wood-like streaks, sometimes swirling a bit here and there for the woodgrain. Once dry I put another gloss sealer on top. (Most often, I use something like Folkart's Indoor Outdoor Gloss Varnish.)
Other color options are bright red undercoat with black top coat (shown), greyish undercoat with white top coat... ad infinitum. This is great fun to do on old furniture by the way.
I also do the same thing in oils with my fine art painting (without the use of a sealer between layers or on top, of course). Sometimes I even used my kitchen sponge as a brush on a canvas. Other times, I used a old ratty hardware store bristle brush to make the sqraffito lines in the wet paint, then a soft sable or synthetic to put in darker grain lines or knots in the wood, but I'm using the same technique. Once grain lines are established and dried, I will sometimes add more color in glazes. The options are wide open.