While I'm not an expert in art conservation, I am the artist who paints full-time. After years of painting, conversations with other professionals and some research, I can offer my basic guidance choosing oil paints. Feel free to research this topic further via my references or by contacting products’ manufacturers, or any other way you may see fit.
Artists have many choices. Picking the right brand of oil paint can be a challenge. Some brands are promoted so heavily by art supply companies that artists buy their paint without a second thought. When I was a student, the quality of paint hardly ever mattered to me and my most common determinant was the price. Today as I take care of my art, however, my buying choices are strongly influenced by the quality and lightfastness of oil paint.
There are several important properties of oil paint artists should pay attention to. The most necessary information can be seen right on the tube. Don’t buy paint that doesn’t have the following data printed on it.
1. Transparency vs. opaqueness of your paint.
An empty square, half-empty, or filled square-gives artists information about the paint’s transparency. While some colors are transparent, others are opaque or semi-opaque. Some brands just say “Transparent” or “Semi-opaque” as opposed to assigning a specific symbol to it. So when I chose my paint for glazing-applying transparent layers of paint-I look at the square/ or a note on transparency to determine if my paint is naturally good for glazing. Some transparent colors are Gamblin’s ultramarine blue, Michael Harding’s bright yellow lake, or Charvin’s transparent yellow ochre, etc. Opaque or semi-opaque colors are often good for scumbling.
2. Pigments used in oil paint determine the lightfastness (resistance to light) or longevity of your art.
This is the most important principle in choosing your paint. While some basic colors have just one pigment, there are many colors that consist of several pigments mixed together along with oil, fillers, and binders. These “new”, not historical colors give artists a lot more color choices but each pigment present in such paint tube should be checked for lighfastness separately. For example, Winton flesh tint has 4 pigments in it (PW6, PW5, PY42, and PV19).
The pigments are described by letters and numbers. For example, PB15-phtylocianine blue is rated lightfastness I. PW1-lead white is lightfastness I. PR2-Napthol red G- lightfastness II, etc.
Here is extensive pigment information database that lists oil paint properties including lightfastness: http://www.artiscreation.com/
Each company performs its own tests on lightfastness of the oil paint. This information is included on the tube too. It reads either as +, ++ or +++, or lightfastness 1, lightfastness 2, or lightfastness 3 and so on. The higher the number (3-4) the less lightfast the paint is. By nature, browns and ochres are often more lightfast than some funky colors, like alizarin crimson or turquoise. Those colors that have lightfastness 3-4 are fugitive and fade pretty quickly. If you paint professionally, those colors should be avoided painting with.
Artists can perform their own tests as well by exposing 1/2 of paint to the sun (while the other half is covered by black tape or cardboard). Lift the tape in a month of continuous light exposure to see the change in color of your pigment. Artist Virgil Elliott has tested numerous colors of various brands and he included a lot of information about painting in his book "Traditional oil painting." http://www.amazon.com/Traditional-Oil-Painting-Techniques-Renaissance/dp/0823030660/ref=sr_1_1?s=books&ie=UTF8&qid=1414806712&sr=1-1&keywords=traditional+oil+painting
3. Type of oil mixed into the paint.
All paints have some oil premixed into the paint. Linseed oil-is the most stable oil that is also used widely as paint medium by artists. It’s long-lasting and dries quite quickly.
Safflower oil, poppy oil, and walnut oil are other, less stable oils often used as vehicles mixed into tubed oil paint.
4. The amount of fillers and binders present in oil paint.
Various amounts of fillers and binders are mixed into oils as well. They dilute the pigment by “stretching” the paint and thus making it cheaper to the consumer. Fillers and binders greatly affect the consistency and texture of paint. It could affect the drying speed of paint as well. Rublev colors, manufactured by Natural Pigments, don't have any filler in their paint making the oils more stable and with high tinting strength. Like other professional-grade paints, they give artists a lot more pigment placed in a small tube as opposed to cheaper oil paint manufactured in a much larger tube.
-Rublev colors by NP
These are great resources for further research:
The atelier movement- a closed group on Facebook-exists for artists interested in classical painting. The group’s administrator is classically trained artist-Graydon Parrish.
-Artist Virgil Elliot: http://virgilelliott.com/
-Beth Sistrunk's blog: www.bethsistrunk.com
-Douglas Flynt' blog: http://douglasflynt.blogspot.com/
-"The artist's handbook of materials & techniques" by Ralph Mayer: http://www.amazon.com/The-Artists-Handbook-Materials-Techniques/dp/0670837016
Visit my website today for tutorials, art and news: www.veronicasart.com