Oil paint is a very expressive medium to use, with sensuous, tactile textures and glowing colors. However, perhaps because of its association with the Old Masters and other towering figures in the world of art, it is often regarded as having a certain mystique that puts it beyond the successful reach of the novice. In fact, it is a forgiving medium that is easy to work with, for you can simply clean or scrape off anything that you are not pleased with and start again.
How Oil Paints Are Made
Oil paints are made by grinding pigments with a drying or semidrying vegetable oil such as linseed oil, walnut oil, safflower oil or poppy oil. This oil binding medium gives the paint its characteristic appearance and distinctive buttery feel. Pigments ground in oil have a particular depth and resonance of color because of the amount of light the oil reflects and absorbs. The oil also protects the pigment particles, as well as acting as an adhesive to attach the pigments to a painting surface. Commercial manufacturers add to this basic mix to give a range of stable paints with relatively consistent drying times.
Make sure you watch the following video on “How Oils Are Made”
Characteristics of oil Paint
One reason why oil paint has been so popular for hundreds of years is that it is an incredibly versatile painting medium that can be manipulated in many ways. Oil paint is so responsive because it dries slowly, allowing for colors to be modified and moved around on the surface of the painting for some time after they have been applied.
This aspect of oil paint makes it an excellent medium for alla prima painting methods, in which the paint itself can accurately reflect the immediacy of the artist’s response to an image. Once oil paint has dried, it can be overpainted in a number of ways without disturbing or dissolving the original color beneath. This means that a complex layer structure of paint can be built up to create different effects.
Oil paint is different because of its richness and depth of color. This is because the pigments are ground in a drying oil that has a relatively high refractive index (the amount of light it reflects and absorbs). Chalk that otherwise appears opaque white becomes practically transparent when it is mixed with linseed oil.
Pigments vary in their refractive index, which to a large extent dictates whether they appear transparent, semi-opaque, or opaque in oil. When compared to other media, oil paints are the most successful at exploiting the different qualities of opacity and transparency. Over a pure white ground, for example, a thin layer of a transparent oil color has a saturation and depth that is difficult to achieve in any other medium.
Drying and semi-drying oils
The range of drying and semidrying oils used to bind pigments together are made from the crushed and pressed seeds of certain plants. The most important of these plants is linseed oil, which is a golden yellow drying oil and comes from the seeds of the flax plant. The best quality linseed oil is cold-pressed, although most modern oils are hot-pressed.
Poppy oil is a semidrying oil made from the seeds of the opium poppy plant. It is a pale straw color and has long been popular as a binding medium for pale pigments that might be affected by the more yellowing linseed oil. It is popular for alia prima work as it takes a long time to dry. This means that the paint can be moved around for some time after it has been applied.
Safflower oil from the seeds of the safflower plant is similarly pale and slow-drying, and it can be used in the same manner as poppy oil.
Walnut oil from the nuts of the walnut tree was very popular in the past for its pale color, and it has been identified as a binding medium for white and blue pigments in many Renaissance paintings. It should be used fresh, as it goes rancid quickly.
Traditional & modern oil mixes: In the past artists used a variety of ingredients in their painting mediums; some caused pictures to darken and crack. Nowadays, a mix of stand oil and turpentine is recommended, and very little resin, if any, should be added.
Traditional pigment sources: Traditional pigments were made from natural sources. The mineral azurite was ground to powder and used as an underlayer for Ultramarine Blue. The red and yellow pigments are poisonous and no longer available. Synthetic substances replace now many natural pigments.
Contemporary Painting Mediums
Solvent-free Painting Mediums
REFINED LINSEED OIL: This is the best quality of linseed oil and it can be used to increase flow and slow drying times. It should be used rarely or it should be mixed with an equal amount of Gamsol, as it makes the paint medium to dry slowly.
ALKYD SLOW DRY: Galkyd Slow Dry is a fluid and glossy medium that is used to thin oil colours and to extend working time. When used with one part of oil colours it allows wet-into-wet painting for over a day.
COLD PRESSED LINSEED OIL: This is the most traditional type of oil. Using Cold Pressed
instead of Refined Linseed Oil will result into slower drying times and will also increase yellowing. Cold Pressed Oil should be used sparingly and only with an equal amount of spirit to create a traditional slow-drying, low-viscosity painting medium. Use Refined Linseed Oil or Puppy Oil for modifying painting mediums and colour instead of COLD PRESSED OIL.
ALKYD GEL: When used untouched they are great for impastos, while they increase significantly the drying times of oil colours. When used together with other mediums they increase fluidity and transparency of oil colours. It takes approximately 18 hours for a layer of average thickness to dry, so that it can be painted over without risking of damaging it. When using Alkyd medium the paint dries all over the paint film (film-forming characteristics), as opposed to linseed oil colours which dry from the top to the bottom.
GALKYD LITE: Galkyd Lite can be used to thin oil colours, while making them more transparent and glossy. It is more fluid and less glossy than Alkyd medium. Thin layers take between 24 -30 hours to dry.
COLD WAX MEDIUM: Cold Wax medium is a soft paste that can be used alone as a matte varnish or to make oil colours thicker and more matte. As it does not contain any oil it can be applied a a wax varnish on a dry painting. Cold Wax medium is made primarily from unbleached beeswax, a small amount of resin as a hardener and also a solvent (odorless mineral spirits) to avoid using heat to melt the medium. It takes on average between 7-15 days to dry depending on the resin medium.
If pigment particles were the same smooth shape, size, and weight, they would all need the same amount of oil to coat their surfaces. In fact, each pigment needs a specific amount of oil to reach a desired uniform consistency. Paint with less oil content is less flexible and is liable to crack if you paint it over a color with high oil absorption. This can be avoided using the “fat-over-lean” rule
High oil content pigments (70% or more): Burnt Sienna, Raw Sienna, Burnt Umber, Winsor Blue and Green, Alizarin, Permanent Rose, and Cobalt.
Medium oil content pigments (50-70%): Cadmium Yellow, Cadmium Red (above), Raw Umber, Oxide of Chromium, and Ivory Black are included in this category.
Low oil content pigments (50% or less): Ultramarine (above), Manganese Blue, and Flake White.
Mixing oil paints
Making your own oil paints is not difficult. You need a ground glass slab and a flat-bottomed glass muller (these are also available in hard stone, such as granite), a large palette knife, cold-pressed linseed oil, and some pigment powder. Avoid using toxic pigments such as Lead White or Cobalt Blue, as they are too dangerous. You should use a dust mask whenever you grind powder colors.
Watch the following great video “On mixing Oil paints”
Modern commercial paints
Commercial oil paints are sold in tubes, and most manufacturers produce two lines: artists’ and students’. Artists’ paint is of a higher quality, as it contains the best pigments and has the highest proportion of pigment to drying oil. The price of individual colors largely depends on the cost of the raw material used to obtain that particular color.
The wide range of cheap, bright, lightfast synthetic pigments now available are a good option.
Paint and other materials
There is a wide choice of oil paints available in tubes or pots, varying in strength of pigment and quality. The best quality paints are professional or “Artists’ colors.” These contain stronger pigments than “Students’
The 15 colors below make up a useful standard palette. With this number of colors, you will have a good ready choice when painting, because with these you will be able to make virtually any color by mixing two or more together. You may want to add a few more colors that you particularly like. It is often economical to buy the colors that you use most, such as titanium white, in a larger tube.
The drying time of Artists’ oil colors can vary from a few days to a few weeks, depending on how thick the paint is applied. Alkyd paints are faster drying oil paints, and their drying time is a fraction of that of:
- Cadmium yellow
- Prussian blue
- Burnt umber
- Yellow ochre
- Sap green
- Raw umber
- Cadmium red
- Viridian green
- Ivory black
- Burnt sienna