Beyond Pigment and Oil: The Useful Additives in Artists' Oil Paints
Beyond Pigment and Oil: The Useful Additives in Artists' Oil Paints
Brushes at the ready, artists! This blog post is set to debunk common misconceptions about additives in oil paints, particularly the notion that they’re the ‘bad guys’ of the palette. Through an informed journey into the art of paint formulation, we’ll uncover the indispensable role that additives play in surmounting the natural limitations of pigment and oil.
Get ready to arm yourself with knowledge, as this guide empowers every artist to make well-informed choices in their noble pursuit of creativity.
The Basics of Oil Paint
Oil paint is essentially a mix of pigments (colored powders) and a drying oil, which acts as a binder. Linseed oil is a popular choice, but others like safflower or walnut oil are also used. When you blend these two basic components, you create paint that can be applied to a canvas. It’s important to note that oil paints dry through oxidation, not evaporation. This means that the drying process involves the interaction of the oil with oxygen, resulting in a solid film.
Following are some potential problems:
Different Drying Times
Relying solely on pigments and oil can lead to several issues. One of them is different drying times. Different pigments absorb oil at different rates, which means parts of your painting may dry faster than others. Furthermore, certain pigments can catalyze the oxidation process, speeding it up, while others may slow it down. For instance, pigments like Lead White and Cobalt Blue speed up drying times due to their inherent chemical properties. On the other hand, pigments like Ivory Black and Titanium White tend to slow down drying times.
Different Viscosities
Another issue is the variation in the thickness or viscosity of paint. Thinner viscosities allow the paint film to level out more, creating smoother surfaces. In contrast, thicker viscosities allow the paint film to hold brushstrokes better and enable impasto techniques, where paint is laid on the surface in thick layers.
Oil/Pigment Separation
Sometimes the oil and pigment don’t bond properly, causing them to separate. This separation can be due to several factors, including the inherent properties of the pigment, the age of the paint, and the environmental conditions in which the paint is stored. The incorporation of stabilizers and surfactants, like beeswax, in the paint formula can help in reducing this separation, ensuring a more homogeneous mixture and consistent application on the canvas.
Uneven Gloss
The variations of oil absorption can result in a painting with sections that are more glossy or matte than others. More oil tends to create a glossier finish, while less oil might result in a matte appearance. For instance, using a pigment that requires a higher volume oil to be properly bound, like Lamp Black or Raw Umber can result in a glossier finish compared to using a pigment that requires less oil, like Titanium White or Prussian Blue.
Note: In this discussion, the ratios mentioned are in terms of volume. This is because different pigments have different densities and measuring oil/pigment ratios by weight would give misleading information for our purposes.
Agglomeration and Clumping
Agglomeration and clumping of the pigment particles might not sound like a big deal, but they can significantly impact the visual allure and handling characteristics of the paint. Many pigments resist dispersion within the oil binder and tend to agglomerate or clump together. This can reduce the color strength of the paint and alter the way the pigment particles scatter light. Dispersants are used to reduce this effect. Some difficult to disperse pigments include Carbon Black, Titanium Dioxide, Phthalo Blue and Green, Iron Oxide pigments, Ultramarine Blue, and the Cadmium Pigments.
A few solutions:
The Magic of Additives
Additives are included in oil paint formulations to counteract these problems. Some of the common additives are:
- Driers: Cobalt and zinc are examples of metal-based driers that speed up the drying process to create a more uniform drying time across different pigments. On the other hand, certain oils like poppy seed oil can slow down the drying process.
- Stabilizers: UV stabilizers, for instance, improve the paint’s resistance to ultraviolet light, ensuring colors remain vibrant for longer periods.
- Alkalis: Additives like calcium carbonate can be used to neutralize the acidity in oils, which increases the paint’s shelf life. Alkalis also contribute to making the painting more archival by preventing the deterioration of the painting's surface or substrate.
- Wax and Fillers: Beeswax, besides being a filler, acts as a surfactant to prevent oil/pigment separation and adjusts the paint’s consistency, ensuring a smoother application.
- Extenders: Increase transparency and create more volume without altering the color.
- Dispersants: Dispersants are an important category of additives used in artists' oil paints. They serve to evenly distribute and stabilize pigments within the binder, which is especially vital when dealing with pigments that are difficult to wet. Som commonly used dispersants include Lecithin, and Polymeric Dispersants. Surfactants also, help as does the use of High Shear mixing techniques.
Further Quality Considerations:
Student Grade vs. Professional Grade Paints
There's also a distinction between student-grade and professional-grade oil paints.
- Student Grade: These are more affordable and generally use lower-cost pigments, which can reduce the vibrancy and saturation of the colors. They often contain more fillers and extenders, which means they may not be as durable as professional paints. However, they are excellent for practice and learning techniques.
- Professional Grade: These contain a higher concentration of high-quality pigments and may also include high-quality additives that enhance the performance and longevity of the paint. Because of the higher pigment concentration and fewer fillers, artists may find that they need to use less paint to achieve the desired effect, which can make them more cost-effective in the long run. They are typically more expensive, but the investment can be worthwhile for serious artists.
In Conclusion
The “best” oil paint is subjective and can vary depending on an artist’s needs and preferences. While purity in terms of pigment and oil might be idealized by some, the additives in oil paints serve practical purposes that can significantly improve the painting experience. Understanding the components of your paint can empower you to make informed choices that suit your artistic vision.
Armed with this knowledge, you will be able to more accurately evaluate the claims of the different paint manufacturers and choose the paints that meet your needs. There is no single “best” paint regardless of what the manufacturers say. Remember that most of the paint manufacturers formulate their paints very carefully, so almost all of them are “good” paints.
A later blog post will address how to select paint for your art practice.
Here's to your artistic journey!
