Fat over Lean Rule

It´s common to hear at painting studios about the fat over lean rule. This is the first rule a beginner learn from his teacher when painting in oils. Although most painters works through a direct approach painting the whole work into a single session, sometimes we need a number of stages of sessions, composing the work in a layered manner. That said, it´s important to understand that, when we paint alla prima, the fat over lean rule is not important, but when we use different stages, in an indirect way, it´s safer to stick to the rule.

It´s very easy to understand the rule: when you add medium to your paint like vegetable oil, you got fat paint. The less oily the paint gets, like when the paint is used directly from the tube without adition of medium or when it´s mixed to a solvent (like turpentine), you got a leaner paint. If the rule is fat over lean, that means the artist should paint with leaner paint first and with fat paint afterwards. That means leaner paint on the bottom and fat on the top: fat over lean.

Working Method
One way of using the fat over lean rule is to start your painting using some solvent, like turpentine, into your paint. You can dip your brush into the container of solvent and mix the paint with the turpentine. This way, your first layer will be painted with a leaner mixture, because its mixed with the turpentine. Into the next stage or layer, paint with oil paint direct from the tube, without any additions. In the next layer, work your paint adding some vegetable oil, like linseed oil, into your paint. This way, into each layer there is a higher concentration of oil, making each layer more oily, following the rule of fat over lean. 

Another way of using the fat over lean is to have pre-mixed mediums, ready to use on containers, adding them on different stages on your work. You can make three different mediums with different proportions of linseed oil and turpentine.

The first medium, the leaner one, might be just turpentine or turpentine with a small amount of linseed oil. Second medium might be 50% turpentine and 50% linseed oil. The third and more oily medium be pure linseed oil or 1/3 turpentine and 2/3 linseed oil. Keep in mind these numbers and proportions are just an example and may be adjusted to your own taste and needs. The only important rule is to make a progression from an leaner mixture to an oily one. It´s good practice to always use the same amount of medium in each layer, so try to dip your brush into the mediums and mix it always using the same amount of medium and paint, so there is always the same ratio on every layer.

Simplier Way
The use of pre-mixed mediums for each stage of the paint might be a problem if you use too many layers, resulting into an complex and unpractical way of working. Dont overthink the problem, keep it simple. First of all, the fat over lean rule was created to make sure begginers respects the drying time of each layer. When you add oil to your paint the fat content makes the drying time much longer, this way layers on top (more fat) dries slower than under layers (leaner), a smart and easy way to be sure no crack, fissures or craquelures appears on upper layers. With this in mind, let´s put the fat over lean aside for now and think differently.

Two variables play an important rule here: drying time and paint thickness (or quantity), both directly related. If there is many layers into an painting and if the top layers are drying faster than the bottom layers, the bottom layers will have more time to expand, to move, during the drying process, resulting on cracking the upper layers. This way, it´s really important to respect the drying time between layers. 

It´s simple and uncomplicated. If you work with layers, just make sure to wait till everything is truly dried before starting another layer: if your first layers are completely dried, there is no need to apply any medium to your paint, as long everything is dried. That means to sometimes wait more than a week depending on the pigment used on the area. The weather and humidity might also extend or diminish drying time. If you cant wait, the solution is to use dryers or in a more practical way, working alla prima and not through layers. A common strategy to gain time when painting in layers, without using dryers, is to paint different canvases at the same time alterning between works. 

Painting by Lucian Freud: Heavy impasto drying slowly

Some artists paint very thinly, using their brushes with little paint, creating a very thin film on the final painting. Other artistas use much more painting, loading their brushes much more, creating the famous impasto effect, leaving a lot of texture on the surface. The quantity of paint used and thickness of the paint will alter the drying time. The more paint we use, the longer it will take to dry, truly loaded layers of paint take years to get fully dried, while thinner layers will take much less, usually dried within a few days. 

That is why drying time and thickness can make the fat over lean rule even more difficult to understand. To make it everything safer, keep in mind to always paint with thin layers first and if you must create more thick layers, make sure they come later, that is, on the top. First layers must be thinner and later layers must have more paint.

There is a third variable that must be considered. Some pigments dry faster or slower than others. So, when working in stages or layers, you must consider not only the amount of fat on your medium, the thickness and order of your layers but also, the particular drying time of each color used. If you build an entire layer made with burnt umber, tha drying time will be much faster than if you build an entire layer containing cadmium colors. So, it´s logical to use fast drying colors on the first layers and slow drying colors on the top layers.

Remember that everything turns more complicated when there is too many layers, if you paint alla prima or with just a few layers, lets say two or three, everything is simplier and safer. Ultimately, when working with different stages, the important thing is to have patience and wait for the last layer to be fully dried, and not half-dried or dried just to the touch, before advancing for the next one. You might want to be on the safer side and make sure everything dries proprerly adding one or two drops of some drier and ensure to keep the drying time shorter. This is specially useful on the bottom layers so you can move to the final layers sooner.

For final thoughts, always remember the following:

• Avoid work with too many layers. If you must use different stages, use at the most, three or four.
• Lean mediums on the first layers and with fatter mediums later.
• Thinner layers first and thicker layers later.
• Fast drying colors first, slow drying colors later.
• Respect the drying time of each layer.

BIBLIOGRAFIA
THOMPSON, Daniel V. The Materials and Techniques of Medieval Painting; Dover; New York.
LAURIE; A.P.; The Painter´s Method´s and Materials; Dover; 1967.
DELAMARE; Guineau; Colors: The Story of Dyes and Pigments; Harry Abrams; 2000.
MAYER; Ralph; Manual do Artista; Martins Fontes; 1950; 1957 e 1970.
EASTLAKE; Sir Charles Lock; Methods and Materials of Painting of the Great Schools and Masters; Dover; 1847

Differences Between Direct and Indirect Method of Painting

It´s important that the painter understand the two different approaches to painting used by the old masters, wich are completely distinct on their ways. They both have different appearances, technical difficulties and ways of procedure and when you must choose wich method to use, you better understand not only their aesthetic appearance, or their final effect, so to speak, but how to procede on these very different methods of painting.

Direct Method - Alla Prima

The direct method is also called "alla prima", from the italian expression "made it in one sitting" or "at once". The idea is to complete in one session the entire painting, without pauses or long breaks. Some people have a bad time trying to understand this concept, on how long exactly is supposed to last a painting session to be called a alla prima work, but it´s easier to understand the method when you think that the painter works his paints while they´re still wet. 

That means the painter will not wait for any particular stage or area to be dried in order to advance on his paint, he is gonna work the paint wet on wet, mixing and converging colors all at once, constructing and solving the whole of the image while everything is still wet, or as we call, while still "open". This way, colors and gradients are fused together into a more painterly and loose way. It´s possible to observe defined and crispy brush strokes characteristic from this method, this "look" is easily detectable even by untrained eyes. This method is used for those who wants to reach a more fresh and loose effetc. Examples of direct method used by famous painters is the works of John Singer Sargent, Anders Zorn and the spanish master Joaquim Sorolla. Some Old Masters also had a more direct way of painting, although occasionaly using some indirect touchs, such as Diego Velasquez, Rembrandt van Rijn and the italian master Tiziano Vecellio. 

Self-portrait, by Tiziano Vecellio (1562)

Indirect Method - Velatura and Glazing

The indirect method is done through a series of stages or layers, usually waiting for each stage to be completely dried before moving on to the other. Since it´s not made "at once" it´s called indirect, reaching results into an indirect way. The advantages of the indirect painting are the use of transparent paint, this method of applying translucent paint is called velatura (glazing), creating optical effects you cant create using opaque paint (direct method), wich is an easy and fun way to work, since most of the time you solve all the values first and lay in the colors after that. The velaturas are thin and transparent layers of paint, this way you can see the previous dried layers under the velaturas. 

The colors on the velaturas united with the colors of the previous layers will form the optical effect characteristic of this method. This way of work takes more time than the direct method, since you must wait for many layers to be completely dried in order to move on. Some artists working on this method will use many layers to build an painting, while others might use just two or three stages. The use of too many layers might be a little risky for the painting, since too many layers might cause the colors to get too dark.

The richness you can obtain with this method when used in the right way is truly beautiful and anyone can see the incredible depth of the velatura on the works of artists such as Leonardo da Vinci, Raphaello Sanzio and Michelangelo Merisi da Caravaggio. It´s important to observe that this method also create paintings without any marks on the paint surface,  when theres too much layers and glazing used on an painting the brushwork tends to level out, causing an flat and difuse overall effect

Portrait of Margarita Luti, by Raphaello Sanzio (1516)

REFERENCES USED FOR CONSULTATION 

MAYER; Ralph; The Artist´s Handbook of Materials and Techniques; Viking; 1950; 1957 e 1970.

GOTTSENGEN, Mark David; Painters Handbook; Watson-Guptill; 2006.

AMIEN; Art Materials Information and Education Center; 2014.

ACMI; Art & Creative Materials Institute; 2014.