Why Oil Paint?

Oil paint was officially invented in the 15th century in Italy/Greece. Usually paint was a mixture of pigment and egg. Jan Van Eyck was one of the first in Europe to add oil paint to pigment. When his paintings were first seen everyone thought it was an incredable invention. It trapped the light and increased the colors intensity. He invented it because he wanted to make his paintings as realistic as possible, with every little detail. Temera paint, which had been used before, dried much to quickly and didnt allow him to make the detail that he wanted. Oil paint dried much slower and allowed him to make better and smoother changes between colors and light making his painting more realistic. Later Leonardo cooked the paint and added 5-10% beewax, which made the color lighter.
Oil paint has been continued to be used by artists and painters because it allows them to rework their paintings to perfection, you can completely erase or paint over things and made extremely smooth gradients of color.