Vive le difference

History recognizes Claude Monet, Auguste Renoir and others as the heroes of impressionist painting. Conservator Perry Hurt adds artist John G. Rand and a host of scientists to the list of people responsible for this French revolution in painting.

Hurt spent five years studying the history of paint and its impact on the way paintings look. The N.C. Museum of Art displays the fruits of his research in "Revolution in Paint," a one-room exhibition in the European galleries, to your left as you approach the stairs down to "Monet in Normandy." A few of the contrasts:

Prussian blue vs. cobalt blue

In the late 19th-century, an artist's palette might contain 15 pigments: white, black, earth tones, red, muted yellow, Prussian blue and precious natural ultramarine blue. The Monet palette is vivid with colors made possible by the discovery of new elements: among them cadmium, chrome and cobalt.

Of particular importance among the new pigments were chrome yellow, synthetic ultramarine, viridian and emerald green. This gave the impressionists a brighter range from which to create their colors.

Black vs. white

Michel Eugene Chevreul, hired by the Gobelin tapestry firm in Paris to develop new dye colors, advanced the understanding of light and color theory. White light was understood to be the mixture of all colors, black the absence, leading some impressionists to ban black from their palette.

A giant mound of white pigment is central to Monet's palette. A brush loaded with white paint as well as color created the light-filled appearance that distinguished impressionist painting from its darkly layered academic counterparts.

Bladder vs. tube

In the 19th century, paint was stored in a pig's bladder (left). If unopened, it would preserve the paint up to three months. A painter would prick the bladder to tap the paint and reseal the vessel with a stopper. Paint would often seep out.

In 1841, painter John G. Rand invented the collapsible metal tube. Not only could paint be stored longer, but it could also be transported to outdoor sites. Because the painter could lay out small amounts of paint, he could develop a composition all over, without the worry of waste that forced earlier artists to work in segments.

LInseed vs. poppyseed

For centuries, linseed oil was the predominant binder for oil paints. With the invention of the paint tube, slower-drying poppyseed oil became the preferred binder.

Where linseed oil tended to flatten out pigment as it dried, poppyseed oil maintained the pigment's texture, retaining the mark of the brush and the thicker spread of the palette knife characteristic of impressionism.