The beginning of the widespread use of oil paints occurred between the 14th and 16th centuries. Finnish artists mixed oil paints with other common paints of the time early on, but oil paints used on their own were not popular until the end of the 15th century. Oil painting use was altered and made better over time by legendary painters such as Leonardo da Vinci, who combined oil paint with wax. Today, most oil paints are combined with various oils that are known to reduce drying time and prevent cracking or crumbling of the paint.
Since oil paints were not regularly in use until the 15th century, many people think that is when they are invented. This is not the case, though. In fact, there is evidence of oil paints being used on cave walls in Afghanistan in the year 650 AD. However, oil paints were not used for many years after that and never enough for them to be considered worthy of mention or distribution. During the later years of the 15th century, oil paint began to see wide use and began to be experimented with to create various effects.
The slow drying properties gave artists the ability to work on a piece for weeks at a time before the paint actually set. This slow drying process also made way for the invention of tube paint, which was invented in 1841. By being able to take premised oil paints with them, artists could paint wherever they wanted. It is said that tube paint, and therefore oil paint, is directly responsible for art's Impressionist era.
Perhaps the most important feature of oil paint was that it has what is called a long open time. This means that the paint can be manipulated for days or weeks before it sets, giving artists more time to blend and finish a piece. Because of the thicker consistency of oil paint, it blends in very subtly with other colors, so more defined and unique blends can be achieved. Upon their invention, they quickly became the most used type of paint in portraits because they have a translucent surface quality similar to human skin.
When oil paints were first produced, a number colors were made with toxic compounds that endangered the health of the users. An example of older toxic oil paints is emerald green, which is made with copper-acetoarsenite, a dangerous poison. Some of the toxic colors are no longer made, though certain ones are. If you choose to work with a toxic paint, always wash your hands or wear gloves when handling it and never ingest or breathe near the paint.