There are lots of materials that can be used to express your paintings in different canvases. One material that is commonly used is oil. When using oil as a medium it must be able to hold pigments together and protect tem from chemical change and dispersion. It must also be able to create something that is of right consistency that can be used on the canvas by either panting knife or brush. Oils must also be able to bring out the properties of each pigment and preserve them in drying to a tough, flexible layer.

There are there main groups of oils:
• Essential oils – used as thinners because they evaporate
o Oil of lavender and spike –is best used for thinning oil varnishes
o Distilled Turpentine – is a good solvent for resins especially when mixed with fixed oils. The oil often favored for mixtures is gum spirit in a less purified form.
o White spirit – useful for giving layers cohesion and dries quickly. This oil sinks beneath the layers of paint layers, oils, carrying waxes, resins. This substance is uses to also clean brushes.

• Fixed oils – dries and binds the pigment of a tough surface. When oils undergo a chemical change they dry, but they do not really dry but only oxidizes. The process of oxidization is a long process that’s why oil paintings are not varnished until six months.
• Oils suffer two defects when aging. They become yellow and become more brittle. Drying agents such as siccatives are used to prepare faster drying paint but it can cause more dangers.
o Linseed oil – dries easily but does not crack easily but top layers yellow when aging. When properly prepared it can be brushed easily, disperse the pigment well, has the right consistency, dries quickly, binds and protects the pigments in a tough flexible skin.
o Poppy Oil – it yellows less than linseed oil but becomes more brittle and cracks easily if not applied properly. It usually dries four to five days.
o Nut oil – nut oil is good for fluid brushes but does not keep well. It dries three to four days and does not yellow so much.
o Stand Oil – is a thick oil that is prepared from linseed oil in an air free environment. It is often thinned with turpentine. Dries for five to eight days, ages well and gives a glossy finish. It I often used to glaze.
o Safflower oil –it is like poppy oil but dries faster
o Sun thickened oil – an oil produced with siccative that is left under the sun for weeks or months. It is better than stand oil because it is more viscous, dries faster, more elastic and durable. It is usually prepared linseed oil that is refined, but any oil can be refined to.
o Boiled Oil – linseed oils that are boiled with a drying agent. They dry fast, glossier and more durable.

• Balsams, resins and varnishes – they improve the flexibility of oil layers, protect fugitive colors, and modify their reflecting properties and makes them glossier.  They provide a transparent protective layer that vanishes and makes the painting medium glossier and clearer.
o Venice Turpentine –made from resin from larch that protects fugitive colors well
o Damar resin – extensively used in retouching varnishes
o Mastic – inferior to damar and more expensive
o Copal – gives a great gloss and strength when used as painting media. It becomes darker in time but cannot be removed easily with ordinary solvents.

So that your painting may not be wasted by using improper oils, try to get a help of an expert first. If you are not to find an expert to guide you, painting by numbers will help you start.