Why did Pierre-Auguste Renoir and other Impressionists avoid using black paint in their early work?

In their early work, Pierre-Auguste Renoir and other Impressionists avoided using black and gray in shadows because they considered these colors to be inaccurate representations of how light and shadow appear in nature.1

Instead of using black, the Impressionists utilized complementary colors to render shadows and capture the effects of natural light. This technique was part of their broader effort to move away from the traditional, muted landscape palette and instead record the vibrant, transient effects of sunlight and reflected light as registered on the retina. By using discrete flecks and dabs of pure, contrasting colors, they aimed to evoke a sense of broken-hued brilliance and shimmering light.1

It is worth noting that Renoir’s perspective on this changed later in his career. Following his travels to Italy and his study of Classicism in the early 1880s, he concluded that black did not deserve the negative reputation it held among his peers, finding that it could provide striking effects and intensity to other colors in certain compositions.2