Saturday, December 19, 2009
Fat Over Lean: Do's & Don'ts Of Underpainting
A good friend of mine and fellow artist Kim Coyne of Greenville, SC wrote me recently to ask about a phrase she heard at some art gathering. She wanted to know what someone meant by saying “fat over lean”.
“Fat over lean” is a phrase that easily reminds artists how to prevent layers of paint from cracking. You see the more oil a paint has in it, the more “fatty” it is considered. So the paints with less or no oils in them are considered leaner. If an artist remembers to paint in layers according to the phrase “fat over lean” he will remember that underpaintings can often be done in watercolors or acrylics while the top and final layering is done in oil, and never the opposite. Now while I was writing this article, someone asked if when painting with oils can the underpainting be done in oil paint also. While the answer is technically yes, the oil painting artist of today will probably do his underpainting in acrylic because it dries in 20 or 30 minutes with the same effect. If an oil painter wants to do his underpainting in oils also, then he will need a lot of time.
In a recent post in which I discussed “The Chemistry of Oil Painting”, I mentioned that oil paintings dry very slowly. Chemically the oil paints dry by forming a dense layer over the top called a film and this film allows the paint to oxidize – a chemical process similar to drying. Acrylics and watercolors dry much quicker through the evaporation of moisture in the paint. So if you have a layer of acrylic paint that becomes already dry and brittle on top of a layer of oil paint that is not quite dry, filmy and hence more flexible… you’ll end up with a flaking, cracking effect and the painting will continue to erode until the water-based (lean) paint totally flakes off.
Most all of my mentors and teachers in the art community have used an underpainting of some sort or another. Underpaintings no matter how simple or elaborate, allow certain shades to show through and sometimes help the painting on top to be crisper, richer and pop a little more. For example when I attempt to paint a blue sky I will often use an underpainting of a complimentary color… usually an ochre or orangey color. (check your color wheel if you’re not familiar with complimentary colors) I paint the white canvas in the desired complimentary color with acrylic paint, allow it 20-30 minutes to dry well and then I begin my sky with oils. Wasn’t it Rembrandt who also painted in layers to create his warm glowing skin tones in portraits? Do some research, check it out! And in the meantime remember to paint oils on top of water-based paints… or as we say “fat over lean”.
The above photo was taken by my buddy and mentor Mildred D. Dunevant in Hillsville, Virginia this weekend. Here in Edgefield we dodged the snow, but as seen in Mildred’s photo she might have a white Christmas.