OIL PAINTING INFORMATION
Oil paints are pigments combined with oil, usually linseed oil, either raw or refined by mechanical means without chemicals.
Due to the varied influence of pigments on oil, various driers may be added to encourage more uniform drying of the paints.
Stabilizers (waxes, water, inert pigments) may be added to keep the pigment in suspension and the oil from separating during periods on the shelf.
While painting, most artists use a glaze and oil painting medium that makes the thickest paints more fluid and/or thins the body colour to allow for transparent application of the paint.
A good medium includes Stand oil, Damar Varnish, Refined turpentine, AS Medium No.1, or cobalt drier.
Oils are desired for:
Buttery consistency, allowing flexibility and ease of manipulation;
Colour consistency upon drying;
The freedom to use transparent glazes as well as opaque application; Their resistance to the elements
Their affinity for canvas, allowing the production of very large work on a lightweight substrate.
Universal acceptance as a fine art medium
Oils may be undesirable because of: Slow (up to 6 months) and uneven drying time.
The necessity to use solvents that may cause allergic reactions
Clean up with turpentine or Turpenoid
S - Series number:
The series number of each artist's quality paint is determined by the value of the pigments.
ASTM stands for the American Society for Testing and Materials.
ASTM has a standard which rates paints by their lightfastness. This is done by exposing the paint to unusually strong and prolonged artificial light, and rating them according to the degree to which they have faded or discoloured.
A scale of one (1) to four (4) is used for this.
If your paint has an ASTM rating of one (1) it has excellent lightfastness and the pigment will remain unchanged for more than 100 years.
An ASTM rating of two (2) means that the pigment in the paint has very good lightfastness so that it will remain unchanged for about 100 years.
Fair lightfastness, with an ASTM rating of 3, will remain unchanged for 20 to 100 years, while paints rated ASTM 4, poor lightfastness, or will show discoloration in less than 20 years. Paints that have an ASTM rating of three or four will fade much quicker if they become diluted or thinned with other paints or mediums.
As an artist, especially if you are selling paintings and not just exploring the use of colour, you should try to choose paints with an ASTM rating of one (excellent lightfastness) or two (very good lightfastness), because if you choose a paint that has a low ASTM rating, it is likely that the colours in your painting will fade sometime in the future.