This is how I go about painting an underpainting, and adding layers of color. The process was for "By the Wall," a figurative oil painting I created last year.
After doing a quick sketch in pencil, the first step is painting the underpainting in one to two layers of raw umber and titanium white. There are many different colors and techniques that artists will use for this stage of the painting, but I have found that this way has worked best for myself and the effects I want to achieve with my work. I paint mainly with raw umber, and only use small amounts of the titanium white for the highlights in her skin and dress. The rest of the white seen is just raw canvas for now. The reason I do this is because raw umber dries very quickly--in a matter of a couple days--while titanium white dries very slowly.
If you're asking why I do an underpainting in the first place, it's because it gives me a chance to get all of the proportional problems worked out before complicating things with more color--and also because as the painting dries the layers become more transparent. With using an underpainting first, the shadows in the painting will deepen with age, making the subject seem more alive. For me, a painting that seems as if it's alive, and that it could move at any moment, is the most important aspect of the creation. Artwork needs life, and feeling. Lifeless artwork doesn't stir the viewers curiosity. It gives no feeling.
In the past, I did most of my underpaintings in one layer, but this one I did in two layers. I think it helped deepen the shadows a little more, and gave a little extra depth and expression in the eyes.
As far as the process of painting the underpainting itself, I will usually first paint in the shapes with a coarse hogs hair brush, and then blur and/or soften what I put down with a larger soft brush--usually a broad, flat sable brush. I'll then draw in everything again in more detail with a fine tipped brush, softening it again with a large soft brush, and keep repeating the process until the basic idea of the painting feels right. I'll then paint in highlights on the skin and clothing with titanium white--but not using very much of the color. I'll blend everything again briefly with a large/thick flat sable brush. Then I'll touch up the highlights and shadows once more, and then begin the hair.
I paint the hair fairly quickly with a round synthetic mongoose hair brush. Although I use mainly cheaper brushes for most of the painting, I use expensive brushes on the hair because the more expensive brushes tend to hold paint better, allowing for longer, more consistent brush strokes. It's important for the hair, because I want the lines I paint to flow freely.
For this painting, after everything had completely dried, I added the second layer to the underpainting very thinly using just raw umber.
I add in layers of color using somewhat the same process as the underpainting, painting in the shadows, and softening them right afterwards each time. I'll typically blend the highlights and middle tones after the shadows because I find that the colors get less muddy that way.
I'll then go back and forth between adding shadows, highlights, and blending until it looks right.
Shadows the for the skin are mainly burnt sienna and raw umber, with very small amounts of sap green, thalo blue, and paynes grey in the darker parts. The highlights in the skin are made up of titanium white, naples yellow, burnt sienna, and an extremely small amount of cadmium yellow deep. The red in the middle tones is an extremely small amount of rose madder brushed in after everything is dry.
For color, I will paint as many layers as it takes for the painting to look and feel right. I put three layers of color on this one before deciding that it was finished.
After letting the painting age and dry for around 6 months, I'll varnish it using
Gamblin's Gamvar Varnish. Out of all of the varnishes out there, I like this one the best. It doesn't smell as strong as other varnishes, and it doesn't darken, yellow, or crack with age.
