Fat Over Lean

So I've just begun taking an oil painting class at my university. It's my first experience with oils- something I've been very anxious about trying, because it is pretty daunting, and if you are a spectacular fuck-up, it can also become quite expensive. Anyway, I was sitting there, trying to soak in the wisdom from my professor, amid 20 other girls who are all under the impression that they are painting GODS, and he keeps tossing around the phrase "fat over lean."

"Fat over lean. Remember. Remember to paint fat over lean. Don't forget that you want it fat over lean. Guys...fat over lean. Lean first, then fat. Fat over lean."

He did not care to elaborate. When I asked, I got a very superficial, unsatisfactory answer, so I consulted the internet instead. It's actually a pretty simple concept, which refers to the quality of paint and the associated drying times.

"Fat" refers to the oil content of the paint. Paint straight from the tube has a lot of oil in it and is considered fatty. If you add any other oil medium to the paint, it has even more fat in it. The more fat (or oil content) in a paint, the longer it takes to dry.

"Lean" would then refer to any paint with a paint thinner in it- usually turpentine, or a turpentine-like substitute (like odorless Turpenoid). The more turpentine you add to an oil paint, the leaner it becomes. Lean paint takes far less time to dry.

"Fat over lean" refers to laying paints down according to drying times. Say you sit down to work on a painting. The first layers you're going to do are your turpentine washes. Gradually throughout this sitting, you will work up to thicker and thicker paints until you're simply using the stuff straight out of the tube. The reason for this is quite logical. If your lean layers dry quickly, there's no danger in putting a fat layer over it. However, if you put a fat layer on first, and then throw on a lean layer on top before the fat layer is totally dry, the lean layer can start to crack. That's because as your lean layer dries, it contracts ever so slightly. As the fat layer underneath it dries (at a much slower pace) it also contracts, causing the already-dry lean layer on top to wrinkle and crack.

It would also be pertinent to point out that oil paint straight from the tube can take several days (perhaps a week) to dry. If you're applying the paint thickly, then it may take even longer than that. There's no rule that says you have to wait for the thing to dry completely before you take another stab at it. If it's still wet, just be sure that whatever you're applying is as fat, or fatter than what you were putting on there last.

So remember kids, fat over lean. If you're feeling impatient while waiting for it to dry, get another project going, so that you can alternate between the two. According to Shawn Barber, he regularly jumps back and forth between eight to twenty pieces at a time (fecalface).