Isabella Flores
The fat over lean rule is a technique used in oil painting that describes the structural process of layering paint with a higher oil-to-pigment ratio ('fat') over paint with a lower oil-to-pigment ratio ('lean'). This technique ensures that the paint will properly adhere to the surface and creates a stable paint film. The relative oil content and drying rate of the pigments are important factors to consider when applying this technique. Oil paint dries through oxidation or polymerization, which involves the absorption of oxygen and expansion. By applying lean layers, which have less oil and dry faster, underneath fat layers, cracking and lifting of the top layer can be avoided. Artists can test the drying rates of their paints and adjust their layering techniques accordingly to achieve the desired results.
| Characteristics | Values |
|---|---|
| Fat paint | Paint with a high oil content |
| Lean paint | Paint with less oil content |
| Fat over lean | A technique that describes the structural process of oil painting. 'Leaner' paint is layered beneath 'fatter' paint |
| Fat paint dries | To a more smooth, glossy finish |
| Lean paint dries | To a rougher, more absorbent surface |
| Solvent | Dries by evaporation |
| Paint with solvent added | Dries quickly, goes on thin, and creates a weak paint layer |
| Tubed oil paint | Has a type of oil as the vehicle for the pigment |
| Oils added to the paint | May increase or decrease drying time |
| Curing time | Continues even after oil paint is dry to the touch |
| Oils and mediums | Usually take longer to cure, and create more strength and flexibility in the paint layer than with plain paint |
| Fat over lean | Refers to the idea that each successive layer in a painting should be more flexible than the one before |
| Thinner paint underneath, thicker paint on top | |
| Faster drying, less flexible layers on the bottom and slower drying, more flexible layers on the top to prevent cracking |
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What You'll Learn
'Fat' paint has a high oil content and dries slowly
The "fat over lean" rule in oil painting refers to the practice of applying paint with a higher oil content ("fat") over paint with a lower oil content ("lean"). Oil paint dries through a complicated chemical process that involves oxidation or polymerization. This is in contrast to water media paints like watercolours and acrylics, which dry through the evaporation of water.
Fat paint, or paint with a high oil content, dries more slowly than lean paint. This is because the higher the oil content, the longer the oil binder will take to oxidize. Conversely, the lower the oil content, the faster the paint dries. As such, it is not recommended to place fat paint under lean paint, as this can cause cracking and lifting of the top layer.
To avoid this issue, artists should ensure that each new layer of paint has a higher oil content than the previous layer. This can be achieved by adding a small amount of oil or a medium with oil content to the paint. The final layers should have the highest oil content, ensuring maximum flexibility and durability. However, caution should be exercised when adding oil, as too much can lead to excessive gloss and yellowing over time.
It is also important to note that the drying time of paint is not solely dependent on its oil content. Different pigments absorb varying amounts of oil, and some colours that are typically fat may be rapid dryers, while some lean colours may be slow dryers. Therefore, it is recommended to test the drying times of the specific paints being used to ensure that the fat over lean rule is followed correctly.
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'Lean' paint has less oil and dries quickly
Lean paint, which has less oil, dries faster than fat paint. This is because lean paint is mixed with a paint thinner or solvent, which causes the paint to become more diluted and runny. The solvent dries through evaporation, leaving the pigment and oil binder dispersed sparsely across the canvas to oxidise with the atmosphere. As a result, the paint dries much more rapidly than paint from the tube and appears duller.
The faster-drying nature of lean paint is advantageous for creating initial layers in a painting, providing a base for subsequent layers to adhere to. By applying lean paint first, artists can establish the foundation and structure of their artwork before proceeding with the slower-drying fat paint. This technique ensures that the painting will properly adhere to the surface and helps prevent cracking or lifting of the top layers.
The drying rate of lean paint can be manipulated by adjusting the ratio of solvent to oil. A higher proportion of solvent contributes to a leaner mixture that dries more quickly. For instance, a mixture of 75% solvent and 25% oil would be the leanest, while subsequent layers can gradually increase the oil content, resulting in slower drying times.
While the specific drying times may vary depending on the paint's composition and environmental factors, a general guideline is to categorise paints as fast dryers (drying within a day or two), average dryers (drying within about a week), slow dryers (drying within a couple of weeks), and very slow dryers (requiring three or more weeks). These categories aid artists in selecting the appropriate paints for different layers and ensuring the desired drying rates for their artwork.
In conclusion, lean paint, characterised by its lower oil content and faster drying time, plays a crucial role in the "fat over lean" painting technique. By understanding the properties of lean paint and its interaction with fat paint, artists can create structurally sound and aesthetically pleasing artworks that withstand the test of time.
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The 'fat over lean' rule prevents cracking
Oil paints dry through a process of oxidation, which involves the absorption of oxygen. This causes the paint to expand. If a thin, dry layer of paint sits on top of a layer that is still in the process of drying and expanding, the top layer will crack and lift.
The "fat over lean" rule is a fundamental principle in oil painting that prevents cracking. ""Fat" paint has a high oil content, while "lean" paint has less oil and dries faster. The rule dictates that each successive layer in a painting should be more flexible than the one before. This means that the upper layers, which are leaner and dry faster, should not be placed under the lower layers, which are fatter and dry slower.
To prevent cracking, the layers with less oil content and faster drying times should be placed on top of the layers with more oil content and slower drying times. This ensures that the upper layers don't crack as the lower layers dry and shrink in the curing process. By gradually increasing the oil content of each layer, the painting can adapt to changes in temperature and humidity without cracking.
It is important to note that the layers of lean paint should be applied thinly. These coats should be stiffer and provide a solid base for the subsequent coats, which will have a higher oil content and greater flexibility. By starting with lean coats and gradually increasing the oil content, painters can ensure the stability and durability of their paintings.
Additionally, it is recommended to not add more than 20% of medium to the paint. Keeping in line with the "fat over lean" principle, it is best to start with a small amount of solvent for the initial underpainting as it dries quickly and is lean.
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Paint layers are built with leaner paint beneath fatter paint
The "fat over lean" principle in oil painting is a general guideline to ensure the structural integrity of the final artwork. It is a technique that describes the process of layering oil paint with a higher oil-to-pigment ratio ('fat') over paint with a lower oil-to-pigment ratio ('lean'). This is done to ensure a stable paint film and proper adhesion to the surface. The key idea is to avoid placing a fast-drying paint layer over a slow-drying one, as this can cause cracking and lifting of the top layer.
When it comes to paint layers, it is important to understand the relative oil content and drying rates of the pigments used. "Fat" paint refers to paint with a high oil content, while "lean" paint has less oil. The drying rate of oil paint is influenced by the oxidation process, where the paint absorbs oxygen and expands during the drying phase. By applying lean paint layers first, artists ensure that each subsequent layer dries more slowly, maintaining flexibility and reducing the risk of cracking.
To achieve this, artists can gradually increase the oil content in each layer by adding small amounts of oil or a medium containing oil. This ensures that each new layer is more flexible than the one beneath it. It is important to note that the thickness of the paint does not determine its fat content; instead, it is the oil-to-pigment ratio that matters. Additionally, solvents like turpentine or mineral spirits should be used carefully as they evaporate, leaving behind a leaner layer.
Following the "fat over lean" rule helps prevent unpredictable results and ensures the durability of the artwork. Artists should allow each layer to dry thoroughly before applying the next, and the final layers should have the highest oil content for maximum flexibility and a smooth, glossy finish. However, caution should be exercised to avoid excessive gloss and yellowing over time.
It is worth noting that there is no strict requirement to add oil to every layer. The critical aspect is to avoid placing lean layers over wet, oily ones. As long as the underlying layer is dry, using paint straight from the tube without any medium can be a safe option. Artists can also use water-mixable oil paints thinned with water as a solvent-free, lean option for the initial layers.
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The drying time of paint can be controlled by adding solvents
The "fat over lean" principle in oil painting refers to the practice of applying paint with a higher oil-to-pigment ratio ("fat") over paint with a lower ratio ("lean"). This is done to ensure a stable paint film, as paint with a higher oil content remains more flexible and dries more slowly. Conversely, paint with a lower oil content dries faster and becomes more brittle. By following this rule, painters can avoid the cracking and lifting of the top layer, which can occur when a thin, dry layer of paint sits atop a layer that is still expanding.
The drying time of paint is influenced by various factors, including temperature, humidity, and ventilation. Solvents play a crucial role in controlling the drying time of paint. Solvents are liquid components of coatings known as volatile vehicles. Upon application, solvents begin to evaporate, leaving behind the solid components that form the dry coating film. The rate of solvent evaporation is critical in determining the drying time of paint.
Different solvents have varying evaporation rates, with xylene and lacquer products drying quickly, while mineral spirits generally dry more slowly. The specific coating and the type of solvent used also impact the drying time. Solvents aid in dissolving pigments and binders, contributing to the overall durability of the coating.
The addition of solvents to paint can make it "leaner," meaning it has a lower oil content and dries faster. When working with thick paint or multiple layers, it is essential to apply lean paint first to prevent sealing in oily layers ("fat" paint) that dry more slowly. However, excessive solvent use can break down the paint, as pigments may not mix properly with solvents alone.
To effectively control drying time, painters can adjust solvent selection and ventilation in the application area. Additionally, understanding the characteristics of different pigments and their drying rates through simple drying tests can help guide the application process.
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Frequently asked questions
Fat over lean is a technique used in oil painting that involves applying paint with a higher oil to pigment ratio (fat) over paint with a lower oil to pigment ratio (lean). This ensures a stable paint film and prevents cracking.
Oil paints dry through oxidation or polymerization, which involves the absorption of oxygen. This causes the paint to expand during the drying phase. If a thin, dry layer of paint sits on top of a layer that is still drying and expanding, it can result in cracking and lifting of the top layer.
A paint that is high in oil is considered fat, while a paint with less oil is considered lean. Transparent colours typically contain more oil, resulting in a shinier surface when dry. Opaque colours have less oil and tend to dry faster.
The fat over lean rule suggests that each successive layer in a painting should be more flexible than the one before. Start with leaner paint, which can be achieved by mixing paint with a thinner or solvent, and gradually increase the amount of fat medium with each layer.
While the fat over lean rule is a useful guideline, some artists choose not to strictly follow it. For example, some artists may use a medium-rich paint for the initial underpainting, while others may not add any medium at all in the first stages. It's important to experiment and find a painting process that suits your individual style and preferences.
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