The French term “en plein air” means “out-doors”. Plein air painting therefore refers to the practice of painting an entire finished picture out of doors. Artists have long worked out of doors to create landscape sketches for the preparation of further studio work. The plein air approach, finishing entire pictures out-doors, however, began only in the 19th century, initiated by John Constable in Britain around 1813.
Before the 19th century, artists had mixed their paints using raw pigments from a variety of media, that had to be ground. The inconvenience of transporting the colour materials had confined them mostly to working in the studio. In the 1800s, ready-made oil paint became available, making plein air painting viable. Furthermore, portable easels and canvases were invented, which the 1830 School of Barbizon strongly made use from. Characteristic for their paintings were tonal qualities, softness of form, and loose brushworkMasterful brushwork is often the defining feature of great artists, where the brush becomes an extension of their arm, allowing paint to flow effortlessly onto the canvas. These artists demonstrate a profound understanding of their medium, knowing precisely when to apply thick, textured strokes or smooth, delicate ones. Their skill extends beyond mere color application; it's about the artistry of More, which would inspire the Impressionists in the 1860s. The popularity of painting en plein air further increased in the following decade with the introduction of paints in tubes.