Introduction to Oil Paint Mediums
The oil paint mediums are vegetable oils that are used in oil painting to hold paint pigment together. They can also be used to thin the paint and act as a clear first layer when painting wet-on-wet. This will allow the first paint layer to spread easily.
What other uses do the different oil paint mediums have in the oil painting process? I want to cover the 4 main mediums in this post, and the way they affect the oil painting process. Oil paint mediums also act as drying agents that can change the drying rate of paint on the canvas. The different oils can also have a different effect on different coloured paints.
Only use artist’s oil paint mediums bought from art stores as your painting medium.
Linseed oil is the most commonly used medium. It is relatively quick drying and provides a strong first paint layer when dry. This makes it ideal for oil painting styles where you put a layer of paint above another layer. It has a tendency though to “yellow” over time and this makes it unsuitable to use with white and yellow colours as it will darken these, and other, light colours.
The painters of the Renaissance period would allow Linseed oil to stand and bleach in the sun for a few months. This would thicken and strengthen the oil, reducing its tendency to “yellow” over time. This made it more suitable for the white and yellow coloured paints. It would also speed the drying time. Heating the oil to between 250 and 350 Celsius has a similar effect.
There are various versions of linseed oil available for artists. Each version has different properties related to drying time, yellowing, flexibility and gloss.
Linseed oil is usually the binding oil used in the manufacture of the darker artist oil paints because the yellowing effect that occurs over time isn’t so noticeable.
Poppy oil is becoming as popular as Linseed, as it doesn’t go yellow over time. It is particularly useful as a medium for colours such as whites, pale colours and Blues. It is though a slow drying oil than Linseed oil and produces a physically weaker paint layer.
Poppy oil should never be used in a first layer of paint that will have a linseed based paint over it. The slower drying time of Poppy will cause the faster drying Linseed based layer above, to crack and flake off.
It is also frequently used as the binder of the lighter coloured artist oil paints as it doesn’t yellow over time. Poppy oil is also used in the manufacture of blue coloured paint as it enhances this colour.
Pure Walnut oil is a very slow drying oil that does yellow slightly with time, but yellows less than Linseed oil, and this makes it suitable for the paler coloured paints. It forms a strong layer when it dries.
Sun bleaching Walnut Oil turns into a faster drying oil which yellows less, making it suitable for brighter colours. Walnut oil characteristics put it between Linseed and Poppy oil as an effective medium.
Walnut oil needs to be fresh as It can rot over time. It’s not used so much now because of this rotting.
Safflower oil is slower drying than Linseed, but faster than Poppy and tends not to yellow over time. It also adds gloss and transparency to paint which makes it ideal for the using with pale colours. Safflower oil is used in the manufacture of the Titanium and Flake White oil colours.
Different mediums give artist oil paints different properties
Different types of oil paint mediums have different drying properties and different colour enhancing properties. The fastest drying medium is Linseed oil and it is best used as a medium for the first paint layer. It is also used as a medium for the darker colours because of its yellowing effect on lighter coloured paints. Poppy oil is slower drying and best used with lighter colours and blues. You must avoid using Poppy oil based paints for the first paint layer. Its slower drying time means that faster drying top layers of paints might crack and flake.
And finally; use the oils from the hobby store for painting, and the oils from the grocery store for cooking.