Blog reader Mark asked a good question: “I've asked a few of my oil painting friends about what the term 'oiling out' means and they don't know what it is. Do you know what artists are referring to? I get the idea that they're rubbing oil onto the painting for some reason.”
Yes, Mark, you got it. “Oiling out” means rubbing a little linseed oil or clear painting medium over a dry surface of paint that you worked on earlier. You can apply the oil with a clean, lint-free rag, cheesecloth, or scrub it on with a large bristle brush and remove most of it with a rag. Edit: Some people recommend using odorless mineral spirits and Galkyd (an alkyd painting medium) for the oiling out medium.
Here's a video from Gamblin showing the process. (link to video)
That oil layer resaturates the colors and makes the paint surface more receptive to the new layer of wet paint, so that it will look like it was all done at the same time. Without oiling out, the new paint application goes on too dry and scrubby. You don't need much oil to get the job done--just a hint of oil.
An oil painting manual from 1845 by J.S. Templeton defined oiling out like this: “The surface of colours in drying, frequently assumes a state that renders it difficult to lay fresh colours thereon properly. To correct this, previous to commencing work, the picture must have a little oil, (either Linseed or Nut) sparingly applied to it with a brush and then perfectly removed by wiping it with a soft silk rag, this will be effectual.”
My wife tells me it’s like putting on makeup. Hydrating the skin with a little moisturizer makes it more receptive to make-up. Not that she paints her face very often!
More information from Virgil Elliott
Video from Gamblin about Oiling Out
Traditional Oil Painting: Advanced Techniques and Concepts from the Renaissance to the Present
Gamblin Refined Linseed Oil
Color and Light: A Guide for the Realist Painter