The Three Basic Rules of Oil Painting

These three rules will help to ensure the longevity of your paintings.

1. Lean to Fat: Probably the most important. It refers to to the solvents added to the paint to make it move or flow. Lean means adding only thinner, whether it's gum spirits of turpentine or an odorless paint thinner. Fat means adding only medium to the paint which is normally a formula that includes linseed oil, a primary component of oil paint. A typical oil medium is: 1 part linseed oil, 1 part damar varnish and 1 part thinner (gum spirits of turpentine is the norm but I use an odorless paint thinner as a substitute*). Start out by using all thinner then gradually introduce more and more medium into your mixture.
   
2. Thin to Thick: This refers to the thickness of the layers being applied. Remember that your thickest layers go on last.
   
3. Dark to Light: This is the most difficult for beginner painters to comprehend. For several reasons, which will be discussed at a later time, dark colors need to be applied thinly and light colors conversely, need to be applied more thickly.
   

There are a couple of ways to think about all of this. The first is stability. Because oil paint tends to shrink slightly while drying you want the earlier layers to dry before the subsequent layers so that the upper layers don't split or crack. Think about baking a cheese cake. If you simply put the cake mixture into the oven the upper layer will cook (and dry) first. Then as the rest of the cake cooks and becomes dryer, the top of the cake cracks. Another way to think about this is, as a wall patch. Think of patching a hole in the wall with Spackle and being in such a rush to finish that you don't wait for it to dry before applying paint. The coat of wall paint dries much faster than does the Spackle so the paint will inevitably crack.

The second issue is adhesion. Oil paint needs something to grab on to. If the early layers of paint are lean then the oil in the subsequent layers will be drawn into them pulling paint along for the ride. If they are fat then there will be less room for the additional oil. Which do you suppose would be a better choice to sop up spilled milk (don't cry we're only supposing), a full wet sponge or a relatively dry one. C'mon, you know. The other concern regarding adhesion is sheen. Paint is less likely to bond with a shiny, slick surface than it is with a more porous surface.

Getting back to the three rules, as with any painting rule.....

.....remember it, then, forget it.

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* some sources claim an incompatibility between damar varnish and most odorless paint thinners stemming from the fact that damar varnish is made from damar crystals and gum spirits of turpentine. Odorless paint thinner is a petroleum based product. The result is a cloudy medium (which has never bothered me). Some claim however, that it could have a detrimental effect on the longevity of your painting. If you have any concerns please do your own research.

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