I had intended to have a transparent background on the current painting I am working on, but I got it too dark, and once that happens with a transparent background the only option to lighten it is to paint over it with opaque paint. Below you can see the painting with the transparent background and the beginning stages of the opaque background I painted over it.
This experience of getting my background too dark made me think of a blog entry I had been intending to write about the use of transparent layers of paint. Using transparent paint for backgrounds, or more accurately, for the “underpainting”, or the first layer of paint, is a longstanding tradition in painting, particularly before the impressionists. The impressionists started a new style of using thick paint over the entire surface, often in just one thick layer. But before the impressionists, oil painters tended to paint in thin layers, building up the layers slowly, and, as I wrote, leaving some of the first transparent layers showing. I generally work in this old, pre-impressionist technique.
You can see this use of transparent painting very well in Rembrandt paintings. His shadows are usually transparent brown. Then the lights are painted with opaque paint. Having the white canvas shine through the transparent paint creates a very beautiful, luminous, stain glass- like effect, and this beauty, I assume, is why it became a traditional technique. And it saved paint, probably important back in the days when pigments were expensive and artists had to prepare and make their own paint.
Two other painters who used beautiful under paintings were Pieter Bruegel and Hieronymus Bosch. In this detail of a Hieronymus Bosch painting below, the first layer of paint was the the lower whitish sky, which is a transparent layer. This probably covered the whole surface. Then he gradated the blue in at the top, also with transparent paint. He then painted the buildings on the horizon with a paint color from the sky. Then at some point he added another mostly transparent layer to create the color of the yellow hills in the foreground. Continuing to work mostly transparently, he now built up all the details. At the end he used opaque paint for the final details, such as the blades of the windmill and the leaves of the trees. Since these details are light over dark, only opaque paint would work. Except for these few opaque details, the whole painting is almost like a watercolor painting done with oils, in the sense that the whole painting mostly transparent paint.
In these paintings they had to be very careful not to get the transparency too dark, like I did on my Unicorn painting. Even if they had had enough money for pigment to cover the whole surface with opaque paint, it wouldn’t have been nearly as beautiful.
I hope now that you’ve read this, when you look at paintings in a museum or art gallery, you will begin to notice where painters have left transparent backgrounds showing through and see the beauty it adds to the painting.