Chalk and Butter

If you have had the good fortune to see Diane Leifheit's show (described in my post "Visit 'Meadow Front'"), you have a sense of how luxuriously expressive a medium pastel can be.


But what is pastel? The word simply means paste - in this case, a paste of pigment and binder. However, you may recall: binder is the defining element of a medium. So, the binder which forms the paste determines what type of pastel you have - and not all pastels use the same binder!


Diane is a master of what we call "soft pastel". In this case, pigment powder has been mixed with chalk (or clay) and a thickening agent.

Most people have also heard of "oil pastel". Can you guess the difference? Here, the binder is a mixture of oil and oil-soluble wax.

Picture a stick of butter and stick of chalk side by side. What would happen if you tried to grease a pan with chalk? (-shudder!-) It's easier to imagine drawing a picture with butter ... but I wouldn't recommend it!

Likewise, oil pastel and soft pastel have very different working qualities.

Soft pastel offers the purest, clearest color, as the crystalline structure of the pigment powder is not dulled by any extraneous coating material. It requires a "toothy ground" (that is, a highly textured surface), and it creates a great deal of dust. The color is so concentrated that a little goes a long way, and it layers, smears, and blends on the ground very easily. It is also water soluble.

In contrast, the color produced by oil pastel is deeper but less intense, because the grains of pigment are coated in the oily binder. (Think of dry vs. buttered toast. The crumb is more visible without the butter.) This is not to say that oil pastel (or buttered toast!) is dull - far from it. Just different.


Oil pastel does not require a toothy ground - its sticky binder holds it onto a smooth surface just fine. It is oil soluble, and can be combined with oil paint mediums such as turpentine. It is not dusty, and is often therefore preferred over soft pastel by artists with respiratory concerns. This also makes it much less messy, and more suited for use by small children.

Whereas soft pastels have a virtually unlimited shelf life, oils do not; over time, they will dry and harden. Also, when exposed to heat (such as a sunny window), oil pastels melt.


Due to their divergent working properties, soft and oil pastels cannot be used together.


Recently I read somewhere that the only similarity between soft and oil pastels is the shape of the stick, and that they should be considered quite distinct media. I think this is true.

The best way to understand each is to try them both: not only will you gain experiential appreciation, but you can also decide which works better for YOU.