Chemistry of Oil Paint: Why Paintings Can Last So Long
It may be easy to forget the scientific side of oil paintings while staring at an old artwork displayed in a museum.
However, colors, texture, drying processes, and aging of paintings can be explained by chemistry. Despite the simplicity of the paints, the components work with each other in a very complex way.
What does oil paint consist of?
In its basic form, oil paint consists of two main elements: pigment and oil.
The first element is responsible for giving colors to the painting. Pigments may be natural (minerals, vegetable substances), artificial (chemical compounds) and other types. They are made up of fine particles suspended in the drying oil, usually linseed oil.
Oil serves not only to make paint flow evenly; it serves as the binder and keeps pigment particles together.
Chemical properties of pigments vary and affect how artists use them; that's why some pigments can't be treated like others.
Why does oil paint not just stay wet?
Here's where things get really fun and exciting.
Rather than drying out due to the evaporation of water contained in the mixture, the paint dries out through the process known as oxidation.
The molecules in the oil react with oxygen in the atmosphere and start linking up into a network that gradually turns the liquid into a solid film enclosing the pigment particles.
So, oil paint does not dry. It changes chemically.
That is also the reason why it may take longer for oil paintings to completely cure compared to paintings done with water-based paints.
Where does oil painting originate from?
Even though the use of oils by artists existed long before the Renaissance period, oil painting took on a special significance in the development of European art in the 15th and 16th centuries.
Artists found out that oil paints had certain qualities that were not present in other techniques. Paints made of oils could be applied in very thin layers, making it possible for an artist to give their picture more depth by using the transition of colors.
Furthermore, oils could be used for a relatively long time; thus, an artist was able to blend their colors right on the canvas.
The technique allowed for some new possibilities of creating a realistic picture.
However, why would paintings age and lose their colors?
When it comes to oil paintings that last hundreds of years, one might ask why they would not remain the same as when they were painted.
This happens because chemical reactions do not cease once the painting hardens.
The painting will continue to react with oxygen, light, humidity, and other chemicals. Some paint colors could change due to chemical alterations, whereas the oil-based binder will alter over time as well.
Yellowing is one such alteration.
Over time, oil binder starts to turn yellow. This process may affect the color composition of the whole painting, especially its brighter parts.
This is why the restorer needs to have scientific knowledge in addition to art skills. The chemistry of paints and binders allows determining the way of preservation of the painting.
Art and chemistry are connected in such surprising ways
Oil painting is an excellent example of the way in which science lives inside something that is seen as purely creative.
Every stroke contains substances that have certain chemical properties. Pigment gives it its color, oil affects the behavior of the paint, and oxygen is involved in the conversion of the wet paint into the solid film. Light and environmental factors can affect the process of the changing of the painting with time.
While painting, artists may consider such factors as colors, composition, and emotion; however, all these aspects have chemistry behind them.
This is why I find art so interesting.
A painting is not only something to see but also materials that interact with each other.
The next time you are going to look at an oil painting, do not forget that you are seeing not only colors on a canvas but also the result of the artistic experiments of centuries, material science, and chemistry.
Sometimes, the most beautiful science is not hidden in something unexpected places.
Thank you for reading!
I started this project because I believe art can inspire change and help advance childhood cancer research. If this article meant something to you, consider supporting the mission by exploring my artwork.
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