Oil paintings are the traditional method of painting and are considered the choice for finished masterpieces since the Renaissance. The benefits of owning oil paintings are the incredible variations in visual impressions the artist can create on the canvas for you. It is a very flexible medium, from watery thin washes of colour using a turpentine base through to inch thick impasto marks.
Oil paint exhibits numerous versatile qualities such as opacity for example, which makes it ideal for artist's to express their ideas using magnificent colour and textural qualities of pigments in oil.
The longevity of oil paintings and qualities under light together with their flexibility endears them as a serious choice for the artist and collector. It is possible to undertake repair on them and they are robust enough to withstand life quite well. They are often painted on canvases that don't require a frame, so it is not always necessary to purchase a frame.
Oil painting on canvas tends to be the more expensive option, mainly because they are seen as representing the artist's full potential and that the painting is presented according to accepted art industry traditions or standards. They can take longer to produce and to dry than other types of art such as acrylic or watercolour paintings.
Please note that in terms of materials used to create oil paintings there can be huge variations in quality between materials used:
Canvas quality. Inspect the canvas before you buy or at least before you are committed to a purchase. Is the canvas comfortably taut? Cotton as a material for canvases is a relatively recent invention and has not yet proved as long lasting as the traditional material of linen as a support. Linen is more expensive and if you look at the back of the painting, it tends to look naturally darker and less yellow than cotton.
Are the stretchers sturdy and well made? Quality stretchers should be either a heavy weight soft wood or preferably a hard wood (which you can tell by the weight and of the painting) that resists warping over time and is a very stable support. They normally come with 'keys' or wedges that insert into the edges of the frame which pre-load the canvas with surface tension.
Quality of paint is difficult to find out but a good paint will show in the intensity of colour reflecting off the surface, its rich, clean colour which is bright and pure.
Worth checking if you are interested in gauging the longevity of an oil painting is the thickness of the oil paint surface. In general, the thicker the oil paint surface, the greater the potential for cracks to appear as the paint shrinks as it dries.
The likelihood of this happening is reduced if heavy layers of paint are confined to one off marks or sections of the canvas. 'Fat over lean' is used by oil painters to structure their paint surfaces to give them maximum flexibility to avoid future cracks (layers of oil rich paint is applied to less oil rich underpainting).