Blur Your Edges
I usually start an underpainting with the skin but this time I have started by laying in the dark background so that I have a tonal value to compare my skin to when I do that later.
What I have done for the background is mix burnt umber and my medium made of roughly half mineral spirits and half linseed oil, and painted it on rather thickly while still maintaining the viscosity of oil. Imagine that the mineral spirits are ‘watering down’ the oil and that the burnt umber is like a thickening agent that brings it back to an oily consistency. The mineral spirits dry it out quickly and tomorrow I can work with it again.
After I painted the background I took a brush dipped in mineral spirits and gently blurred the edges. I don’t want to have sharp lines everywhere, but rather a consistency to the painted surface. I think this is one of the many tricks that novice painters don’t know or don’t employ. It may seem unnecessary, but it helps to make a painting look polished.