fat over lean" - No doubt most of you have heard this at one time or
another. It is surprising how many oil painters forget this basic rule,
especially in the heat of the moment when we are out plein air
painting. Paint brushes get flying and dipping into who knows what
solvent or medium - with no attention paid to what we are doing.
Painting teachers seem more interested in making oil painting easy for beginners and don't want to create any technical barriers to just getting the paint on a canvas. Having a "no holds barred" approach is liberating. If you are still in a fledgling stage we don't want to inhibit you in any way.
At some point in our journey as oil painters we become interested in why paint acts the way it does. We also become interested in what we can do with the use of our art material to produce a more technically excellent result.
So here is the recommended way to apply oil paint.
First layer - block in your composition using paint mixed with Mineral Spirits or Turp. This is the "lean" part of the painting. This thinner mixture will be the foundation of your paint layers.
Second Layer - Thicker paint goes over the first layer with the paint straight from the tube or mixed with a little bit of a painting Medium such as Liquin or Galkyd Lite.
Third Layer - if there is one - should be pure paint with no medium mixed with it - typically this may be some highlights or detail that will go over the previous 2 layers of paint after they are dry. As with everything to do with art, we break the rules all the time. It's just helpful to know why there are rules like this. Mixing thinner paint to go over thicker paint can cause problems with cracking and peeling as the painting ages. It also messes up those lovely light reflecting brush strokes that we work so hard for.
Reworking areas of a painting - We often continue to work on our paintings after they are dry. Some painters like to apply a coat of medium to the area to be reworked before applying the new paint layer.
Varnish - Wait for 6 months or until your painting is completely dry before applying any varnish. Remember that thicker paint dries slowly - even though the surface of the paint seems dry it may still be wet underneath. A coat of varnish will bring your colors back to a just painted look and provide the finishing touch to your painting. Varnish also protects the painting surface from sunlight damage as well as grim from other sources. We recommend that you use one of the new varnishes rather than Damar Varnish which tends to yellow with age. Check out GAMVAR by Gamblin Colors.