The main Artist quality oil pastels to look for are; Caran D'Ache, Sennelier and Holbein. Research shows these contain quality products with excellent lightfast and archival properties.
Of the Student grades there are a larger number to choose from, each offering different qualities but the lightfast quality is not usually as good. Try out the different makes, do some research and find what works best for you.

Oil pastels can be applied to most surfaces - paper, mount board, Bristol board, wood, mdf, primed panel and canvas panel to name just a few! Same surfaces as used in oil painting.
They can be used for sketching, drawing and very detailed work. They can be smoothed with the fingers to blend them. They can also be used with other media - over a dried watercolour painting, over a gouache background, mixed with pastels and pastel pencils, with oil paint or over a dried oil painting and with ink - a very versatile media.

There is usually a price to pay for something as amenable as this and for most people it's the framing of the finished art work. Oil pastels never really 'dry', the oil and wax combination stops them drying with a skin like oil paint, you can go back to them years later and find you can still move the oil pastel around. So to protect the finished painting they are most often framed under glass, which is usually more expensive than a frame without glass. There are spray varnishes around that can be used on oil pastels to save framing under glass, this may be fine until the work needs cleaning or conservation - the choice is always with the artist.
 
 

The Oil pastel painting above measures 7 inches by 4.5 inches, it's my first Oil pastel and was painted over forty years ago on watercolour paper.
The oil pastels used were of a lesser quality than can be purchased today but it has stood up well even though it has never been framed under glass or varnished. The oil pastels have hardened but they could still be moved!
How a painting is protected defines the life it leads.

Zest-it Oil Paint Dilutant and Brush Cleaner with Oil Pastels

Furthest left is just oil pastel applied to the paper. I basically held the oil pastel like you would a pencil and laid down lines on the diagonal to apply the pastel. Oil Pastel strokes can be kept very loose and you can draw with them overlaying one colour with another.

Next is the same oil pastel, applied in the same way, this has then been blended with the fingers. You can see that it gently softens the pastel, it still shows the 'hit and miss' effect of the tooth of the paper - it would take more pressure to blend it further. To save on the fingers a blending stump or tortillon could be used.

The next swatch (third from the left) has been blended with a soft flat brush, 'just damp' with Zest-it Oil Paint Dilutant and Brush Cleaner. This gives greater blend-ability and colouring of the paper, it also gives back some of the 'tooth' of the paper allowing more pastel to be applied. You can 'gently' add more pastel to this dampen area to further blend colour and add depth, or wait for it to dry before adding more oil pastel. Although not shown in the above example, subtle difference can be seen, depending on whether oil pastel is added whilst damp or dry.

The last swatch is the same oil pastel blended with a soft flat brush, 'just damp' with Zest-it Clear Painting Medium. The Clear Painting Medium does not spread the oil pastel as much and it stays damp for longer whilst still giving greater blend-ability and colour to the paper. Once the Zest-it Clear Painting Medium is dry the oil pastel is not as easy to move.

With most types of paper surfaces there will usually be some 'drag' of the pastel as you move it across the surface. On less absorbent surfaces, the smooth velvety feel of the oil pastels is more apparent and blending is easier.
 

Saunders Waterford 140 lb paper primed with Blackened Bronze Liquid Metal which has an acrylic base. The paper has retained its tooth but notice how the oil pastel has gone on much smoother and the blending is also more even.
It all depends how you want to work and the look of the finished painting.

From my experience of using Oil pastels - they live a better life on less absorbent surfaces than un-sized paper products and a more rigid surface suits them very well. To give a less absorbent surface to watercolour paper apply a coat of archival Gelatine, Gesso, Acrylic, Permanent Pigmented Ink or Liquid Metal Ink as the primer.
Using a primer makes the paper more rigid, retains the 'tooth' and protects both the pastel and the paper from each other.

This is just a small insight into Oil pastels, especially for those who have not tried them before or are unsure of the possibilities. Get to know your media, the surfaces you can use it on and the products you can use with it, but most of all enjoy yourself.

Copyright© Jacqui Blackman 2000