Oil pastels are pigment held in a soft wax and a non-drying oil. That last part is the whole story. Unlike almost every other painting material, an oil pastel does not cure. A picture you made five years ago is still, technically, wet.
Everything worth knowing about using them follows from that.
First, they are not chalk pastels
Soft pastels, sometimes called chalk pastels, are pigment bound with gum. They are dry, dusty, they blend by smearing powder and they need fixing. Oil pastels are greasy rather than powdery, they do not raise dust, and they behave more like a very soft crayon than like chalk.
The two are sold side by side and are often confused. If it leaves a dusty film on your fingers it is a soft pastel; if it leaves a greasy sheen it is an oil pastel.
Working with them
Choose a surface with tooth
Oil pastel needs something for the wax to grip. Textured pastel paper, watercolor paper, sanded pastel board or a gessoed panel all work well. Smooth copier paper does not: the stick skates across it and the color sits in a thin greasy layer that will not build.
A board primed with gesso is a good and cheap surface, because gesso leaves a fine tooth. Our note on what gesso actually is explains why that texture matters. If you would rather work on canvas, our overview of types of canvas for painting covers which surfaces have enough grip.
For the numbered kind specifically, the tips that actually work start by dealing with two pieces of advice that are repeated everywhere and are wrong.
Build up, do not start heavy
The most common beginner mistake is pressing hard from the first stroke. Once you have filled the tooth of the paper with thick waxy color, nothing further will stick to it, and you have painted yourself into a corner.
Start light. Lay the broad areas with the side of the stick and light pressure, then build the strength of the color in successive passes, saving the heaviest, brightest marks for last.
Blending
Three ways, all useful.
- A fingertip. The warmth softens the wax and it blends beautifully. It is also the reason people end up with rainbow hands.
- A blending stump or a soft cloth, for more control and cleaner edges than a finger gives.
- A little odorless mineral spirit on a brush, which dissolves the wax into something closer to a wash. This is how people get smooth skies and soft backgrounds out of what looks like a crayon.
Scratching back
Because the surface never hardens, you can scrape into it with the end of a brush, a palette knife or a fingernail to reveal the layer underneath. Lay a dark color over a light one and scratch a drawing back through it. This is the one thing oil pastels do that no other medium does as easily, and it is worth trying on the first day.
A trick for detail
Oil pastels soften in a warm room and in a warm hand, which is exactly what you do not want when you are trying to make a small precise mark. Leaving the sticks somewhere cool for a few minutes firms them up and gives you a sharper edge. A knife-sharpened point on a chilled stick will hold for a minute or two of fine work.
Finishing a piece is the hard part
Since the surface stays soft indefinitely, an oil pastel painting is vulnerable forever. It will pick up a fingerprint next year as readily as it would today.
The reliable answer is to frame it behind glass with a mat or a spacer, so that nothing touches the surface. Laying glass directly onto oil pastel will eventually leave the picture stuck to it. Fixatives made for oil pastel exist and help a little with dust, but none of them turn the surface hard, and any article telling you otherwise is guessing.
For storage, keep a sheet of glassine or baking parchment between finished pieces, and keep them flat and cool.
How they compare with acrylic
| Oil pastel | Acrylic | |
|---|---|---|
| Drying | Never fully dries | Touch-dry in minutes |
| Correcting | Scrape back or work over, indefinitely | Wait for it to dry, then paint over it |
| Blending | Easy, at any point, forever | Only while wet, so a short window |
| Color change | Stays as laid down | Dries slightly darker than it looks wet |
| Fine detail | Limited by the width of the stick | As fine as your smallest brush |
| Finished piece | Needs glass and a spacer | Can be varnished and hung as it is |
Neither is better. They suit different temperaments. Oil pastel rewards a painter who likes to keep pushing a picture around and does not want to be hurried. Acrylic rewards a painter who wants a decision to stay made, and who likes putting one layer cleanly over another, which is covered in our guide to layering acrylic paint.
Why numbered kits are acrylic
Three reasons, and they are all practical.
Coverage. Every region on a numbered canvas has a printed outline and a printed number that must disappear. Acrylic is opaque enough to bury them. Wax over printed ink is far less reliable.
Precision. A great many of the regions on a 16x20 canvas are smaller than the tip of a pastel stick. A fine brush can fill them; a stick cannot.
Permanence. A numbered canvas is meant to be hung on a wall and dusted occasionally. Acrylic dries hard, takes a coat of varnish and looks after itself. An oil pastel version of the same picture would need glazing and framing before it could safely be touched.
You can see the designs in the full collection, and our guide for beginners covers a first canvas from start to finish.
