Studio Craft: Impasto Basics

Ask the Expert: “I like the look of thick paint (the thicker the better IMHO). Are there any rules or guidelines for using impasto?”

A: Applied correctly, thick passages of paint can prove as durable as any technique, but improperly applied or excessive impasto can lead to defects or even paint failure.

Flexibility has a lot to do with how broadlyimpasto can be applied. Paint like acrylic whichretains flexibility as it ages can be piled on fairlyheavily. Alternately, oil paint doesn't offer thesame degree of flexibility over time and maycrack if thick passages cover a broad surfacearea. The addition of alkyd medium can helpincrease flexibility, reducing the chance ofcracking in heavy applications.

Movement in the support can impose stress onthe paint film. For this reason, there is adifference in how impasto can be handled onflexible fabric supports like canvas versus rigidpanels. Shrinkage, expansion and sagging in astretched canvas can cause thick passages tocrack, and weakly bonded pieces of paint maydetach over time if the damage is severe.

Rigid panels like hardboard, MDO plywood andhoneycomb aluminum sandwich board cangenerally support much heavier paint thanstretched canvas. Even highly flexible acrylicsmay cause a stretched canvas to sag whenapplied too thickly, so panels should beconsidered any time the weight of the paintmight exceed the strength of a flexible support.

The painting ground also plays a key role in howwell impasto can adhere to the support.Adequate priming is always important, evenmore so when paint is heavy. Careful supportpreparation with a professional quality primer isessential to provide optimal texture andabsorbency so paint can attach securely. Thatway, even if cracks develop, paint will stillremain in place.

A good approach to painting in impasto with oilson stretched canvas is to limit the broadness ofapplication, placing thick passages in smaller,isolated spots surrounded by thinner paint. It'spossible to create the illusion of heavier paint byapplication with a knife, or texture can be builtup in the priming layer, prior to painting withacrylic-based products like modeling paste.

Finally, it's important to consider drying timewhen painting thickly. Even a fast-dryingmedium like acrylic paint can take a long time todry if applied in thick passages. Heavy impastoin oil paint may take as long as a year or more todry thoroughly.

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