How did a humble metal tube send painters outdoors?

The collapsible metal paint tube made oil paint portable, and that let painters leave the studio and work outdoors, "en plein air". Before the 19th century, artists or their assistants ground raw pigments with linseed oil themselves, and the fresh paint was stored in animal bladders. It was messy, awkward to carry and dried out, so most painting stayed indoors.

In 1841 an American portrait painter, John Goffe Rand, patented the first collapsible tin paint tube. Paint could now be made in bulk, squeezed out as needed and capped again without drying out, a bit like toothpaste. Add portable folding easels, and a painter could carry a whole studio into a field.

A generation of young painters seized on it. In the early 1860s, Claude Monet, Pierre-Auguste Renoir, Alfred Sisley and Frédéric Bazille often went into the countryside together to paint in the open air, chasing changing light. Tubes gave them ready-made colours and let them work spontaneously. Renoir was later quoted as saying that without paints in tubes, there would have been no Cézanne, no Monet, no Sisley or Pissarro, "nothing of what the journalists were later to call Impressionism".

Historians add a caution: Impressionism can't be explained by portable paint alone. But a small tin tube certainly helped art step outside.