Oils are used to mix pigments and to modify their properties afterwards. In reading the art supplies catalogue, remember that oils have to do the following:
hold the pigments together, protecting them from dispersion and chemical change
create something of the right consistency that can be applied to the canvas by brush or painting knife
preserve the pigments in drying to a tough, flexible layer
bring out the properties of each pigment
There are three main groups of oils:
fixed oils, which dry and bind the pigment in a tough surface
essential oils, which evaporate and and are therefore used as thinners
balsams, resins and varnishes, which protect fugitive colors, improve the flexibility of oil layers and modify their reflecting properties, generally making them glossier.
A great variety of products are marketed today, and there were even more 'wonder recipes' in the past.
Massey (see below) thought the safest approach would be to use cold-pressed linseed oil in the right proportion with pigment, and leave it at that, perhaps adding a glaze or varnish if necessary. All other modifications increased the chance of the oils yellowing and becoming brittle. There was no harm in using paint as it comes from the tube, therefore quite the contrary, provided only that the paint was properly constituted. Modern paint manufacturers in fact do an excellent job and offer a wide range of paints that last well in tubes and display a common consistency and drying time. Unfortunately, these properties can only be achieved by a) adding inert pigments to improve the brushability, b) adding more oil to prevent hardening in the tube, plus waxes and animal fats to prevent the paint being too runny, c) adding poppy oil to slow drying or d) siccatives to increase drying rates. All this means that the artist cannot be sure just what has gone into the paint and how it will perform in the long term.
Oils undergo a chemical change when they dry, which is not strictly drying at all but oxidation. This process goes on for weeks and months after the oil is dry to the touch, and oil paintings are not generally varnished until six months after completion for that reason.
Linseed oil is generally used in the manufacture of oil paints. When properly prepared it disperses the pigment well, can be brushed easily, has the right consistency, dries within a reasonable time, binds the pigments and protects them in a tough, flexible skin. Poppy oil yellows less than linseed but become brittle more easily and may crack if incorrectly applied. Both oils start drying immediately, however, and paint left on the palette from the day before may adhere or brush less well. The best course of action is to prepare your own paint as needed, even though hand-grinding cannot emulate the smoothness of commercial products.
All oils suffer two defects on aging: they yellow and they become more brittle. Drying agents (siccatives) used to prepare faster-drying painting media and varnishes, may increase both dangers. Massey believed that lead and manganese driers certainly did, although Stephenson thought that the lead drier, properly used, was suitable for boiled oil. Cobalt naphthenate may be added sparingly to actual paint to reduce its drying time, but here again Massey cautioned against its use in underpainting or in thick oil layers.
Dries quickly (12-24 hours), does not crack easily but top layers yellow with time (not lower or underpainting layers, however). Stephenson thought that alkali-refined linseed oil would give adequate results, while Massey insisted on the traditional (and more expensive) cold-pressed variety.
Dries in 3-4 days and does not yellow so much. Good for fluid brush work, but does not keep well.
Dries in 4-5 days, does not yellow, but may crack if applied too thickly or to lower layers of painting.
Thick oil, prepared from linseed oil in air-free environment. Dries slowly, 5-8 days: often thinned with turpentine. Ages well and gives a glossy enamel-like finish. Often used in glazes.
Like poppy oil but dries a little faster.
Produced by leaving oil in the sun for weeks or months, sometimes with a siccative. Even better than stand oil more viscous, quicker-drying, more durable and elastic. Usually prepared from refined linseed oil but any oil can be so treated.
Refined linseed oils boiled with drying agent. Faster-drying, with more gloss and durability. Both Stephenson and Massey had doubts about boiled oil, however, particularly the commercial varieties in which air was blown through heated and sometimes inferior oils.
Essential oils evaporate away, and are therefore used as thinners or a means of dispersing paints already applied.
Dries quickly: mixes well with fixed oils and is good solvent for resins. Gum spirit is a less purified form, often favored for mixtures.
Best for thinning oil varnishes.
Dries in a few hours. Very useful for giving layers cohesion: sinks through paint layers, carrying waxes, oils and resins into layer(s) beneath. It is also much used for cleaning brushes.
These provide a transparent protective layer in varnishes, and also add gloss and clarity when used in a painting medium.
Resin from larch. Protects fugitive colors well.
Used extensively in retouching varnishes etc., dissolved in turpentine.
Expensive and generally inferior to damar. Makes a mellow finishing varnish.
Imparts great gloss and strength when used as painting media. It darkens with age, however, and cannot be removed with ordinary solvents, making finishing varnishes somewhat final. Massey believed that copal should never be used in anything but glazes and varnishes, and remarked that the Manilla copal normally sold was a very inferior product useful only for fixatives. Stephenson was quite happy with Manilla copal, and provided a recipe for resin oil that used copal and alkali-refined linseed oil.
The experts do not entirely agree. The best source of recipes is Massey, though Mayer has little good to say about him. Stephenson mentions Massey, however, but ignores Mayer altogether. The safest course is to accept what everyone agrees with, or at least doesn't actually dispute, which means steering clear of copal varnishes, for example.
The second point to make is that there is no one product that will serve all purposes. Old masters prepared paints and media as needed, bearing in mind mixing properties, speed of drying, elasticity, gloss, interaction with other media, and durability. Their general practice was finer paint over coarser-ground paint, and fat over lean (i.e. the lower layers should always be more rigid than the upper ones). Normally this was achieved by thinning the lower oil layers with turpentine, and making sure that lower layers of paint or glaze were quicker-drying than than the upper ones. They worked up from lean paint, through normal paint, to oil-rich fatty painting, glazes and varnish.
There are many advantages in making your own paint. The ingredients are readily obtainable, and the process is straightforward. Paint so prepared is also cheaper (often a third of the commercial price), but the two real advantages are:
paint handles very much better. You make paint with the properties that meet your particular requirements or painting style
you can be sure of what's in your paint, and so be more certain of its permanence
Paint is best ground with a muller and glass slab, but may be prepared in small quantities with a palette knife only, provided it is thoroughly mixed and all grittiness ground out. It is worth noting that French ultramarine often needs an inert pigment added if any consistency is to be achieved, and all pigments have their individual properties, which are readily appreciated when prepared in this way.
Cleanliness is essential. Freshly-prepared paint will keep on a palette for up to a week, though properties will suffer. Linseed oil is the usual medium, but other media may be added to the ground mixture. Paint so prepared may be stored in metal tubes, which are sold by artist suppliers, but of course will deteriorate in time unless preservatives, stiffeners and fillers are added, when the paint becomes no better than commercial varieties.
Massey provides the best information, but his recipes apply more to paintings built in stages, which was the traditional approach, and remains the safest.
Use one of these:
Sun-thickened linseed oil, Venice turpentine or turpentine.
Egg yolk, water and any oil or varnish
Use one of these:
Normal paint thinned with 2-3 times its quantity with turpentine
Media given below and thinned with turpentine
Use normal paint with one of these media:
Damar varnish, linseed oil and turpentine.
Damar varnish and linseed oil
Stand or sun-thickend oil, Damar varnish and turpentine
Damar varnish, beeswax and turpentine
Damar varnish, sun-thickened linseed oil and Venice turpentine
Damar varnish and a wax varnish
Some pigments react together. To prevent this adverse effects consider:
Venice turpentine and linseed oil
Beeswax, Damar varnish, sun-thickened linseed oil and turpentine
Egg yolk and Damar varnish particularly goof for painting wet into wet
Egg yolk and beeswax varnish
See the page devoted to glazes and glazing.
For painters who don't want to bother with such matters, the artist supplies companies offer various painting media. Megilp is a medium used to stiffen impastos and consists of linseed oil, lead dyers, gum mastic and turpentine. Most painters today would prefer Win-Gel.
Information from paint manufacturers is useful start, but you'll probably need to purchase one or more of the books below for detailed reference. We give only a small selection of the many art suppliers listed on the Internet. You can find many more with the search engines, possibly someone local for convenience. There are also trade directories, Yellow Pages and the like. Don't forget to compare prices, terms and shipping charges.
1. Cad-Red. Useful information on oils, pigments and how to prepare paints and canvases.
2. Kama Paints. Online demonstrations on how to make oil paints.
3. 'The Artists's Handbook of Materials and Techniques' by Ralph Mayer. 5th Edition. Viking Press. 1991.
4. 'What Every Artist Needs to Know About' by David Pyle. Krause Publications. 2000.
7. 'The Materials of the Artist and their Use in Painting' by Max Doerner. Harvest Books. 1984
5. 'Formulas for Painters' by Robert Massey. Watson-Gupthill. 1980.
6. 'The Materials and Techniques of Painting'. J. Stephenson. Thames & Hudson. 1989.
7. 'The Artist's Methods and Materials'. M. Bazzi. John Murray. 1960.
8. 'Methods and Materials of the Painting of the Great Schools and their Masters: Two Volumes Bound as One' by Sir Charles Lock Eastlake. Dover Publications 2002. Reprint of classic 1847 text.
9. BigHorn Art Supply Directory. Maintain a directory of fine art supplies worldwide. Excellent coverage : email them for a list of your country's suppliers.
10. Rex Art. Long-established art supplier in Florida with a good range of merchandise.
11. Discount Art. Stocks products of many well-known names at discount prices.
12. Dick Blick. Excellent range of products from a well-promoted supplier.
13. Mister Art. Very large online discount art and craft supply store.
14. Art Express. Another well-known US discount store.
15. Utrecht Online Art Store. Sell their own paints but otherwise a good range of art materials.
16. Lawrence. Leading UK supplier, with 4000+ products, useful advice and downloadable fact sheets.
17. Graphigro. Leading French art materials suppliers with 18000 product line.
18. Art Navigator. Lists art materials suppliers (and much else) in Germany and Austria.
19. Bondi Road Art Supplies. Australian supplier of an exceptionally wide range of pigments: catalogue in pdf format.
20. Art Spectrum. Australian art supplies manufacturer: useful color guide on site.
21. Art Supplies Online. A New Zealand supplier: good range of products and some helpful painting tips.
22. Oils HQ. Not specific to painting, but again with items of interest.
'The Water Seller of Seville' by Diego Velázquez. c.1619. Wellington Museum. London. An early work, essentially in reds but with olive-green in one water vessel and so technically a complementary color scheme.