Traditional oil paint came into use some time around the 5th century B.C gaining great popularity in the 15th century. Oil paints have a rich deepness and dry very slowly allowing the artist to continue to blend and work an area for days. They are created by binding a pigment with an oil, like linseed oil. In order to thin the paint or clean brushes, a solvent like turpentine must be used. These solvents are toxic, highly flammable, and require good ventilation. Over the years, manufactures have invented a variety of products to reduce the issues surrounding solvents. Today, a water mixable oil paint is available allowing the artist to thin and clean up the oil paint while still retaining most of it's great qualities.
Techniques used to create paintings for both types of oil paint are the same. Since water is used to thin paint, there are two steps to the drying process. First, the water will evaporate out of the painted surface followed by the typical oxidation of oil paints when exposed to air. Once the paint is dry, it can not be activated again by water.
Drying time is 1 - 3 days (different colors dry at different rates)
Small amounts of oil like, linseed oil, can be added to slow down the drying time
Paint is permanent once it drys
Artist build up multiple layers to create depth and richness
The first layers are called "under-painting" and use fairly thinned layers of color that help the next layer to "grab the canvas.
Under-painting establishes the tonal range and colors for the entire painting
Thinned acrylic may be used for the under-painting to create a solid tonal base for future layers
Oil paint has a natural glossy finish. Layers mixed with a lot of water will dry matte
For thicker layers, it is best to use an oil rather than water to thin the paint or make it more spreadable.
Oil paintings can be varnished for a glossy look, but must be allowed to dry for at least 6 months before varnishing
Over time oil paints can yellow
Canvas Prep Because of the corrosive nature of oil paint, canvases must either be bought pre-primed or be painted with gesso.
Blending Oils allow for beautiful blended areas. If a hard edge is desired, the surrounding paint must be allowed to dry for a day or so to prevent them from mixing.