Artists find this useful because they can keep working on the painting for a long time. People say that Leonardo da Vinci worked on his painting of the Mona Lisa for four years, even although it is not a very big picture. Oils paints and oil paintings are often just called "oils" for short. If someone talks about "painting in oils" they mean that the painting is done in oil paints.
No-one knows when oil paint was first used. Caves in Afghanistan are decorated with ancient paintings in paint mixed with oils. It is believed that this type of paint was used in other countries of Asia as well.
It is believed that oil paint was used in Europe in the middle Ages at first for decorating shields, because oil paint lasted better than the traditional paint of tempera when it was in the weather, or if it was roughly treated. In 1125 a writer called Theophilus gives information for how to make oil paint in his book called On Diverse Arts.
The Renaissance art historian, Giorgio Vasari, said that the art of oil painting came from Northern Europe and the person who invented it was the famous Flemish painter Jan van Eyck.
Artists from the areas of modern Belgium and the Netherlands were the first artists to make oil painting their usual method of painting. This trend spread to other parts of Northern Europe.
A famous painting called the Portinari Altarpiece by Hugo van der goes arrived in Florence in the 1470s at a time when Leonardo da Vinci was young. Oil paintings at this date were usually done on wooden panels, in the way that tempera pictures were.