Oil painting is
the process of painting with pigments that are bound with a medium of
drying oil — especially in early modern Europe, linseed oil. Often an
oil such as linseed was boiled with a resin such as pine resin or even
frankincense; these were called 'varnishes' and were prized for their
body and gloss. Other oils occasionally used include poppyseed oil,
walnut oil, and safflower oil. These oils confer various properties to
the oil paint, such as less yellowing or different drying times.
Certain differences are also visible in the sheen of the paints
depending on the oil. Painters often use different oils in the same
painting depending on specific pigments and effects desired. The paints
themselves also develop a particular feel depending on the medium.