Since at least the early 17th century artists made oil sketches out of doors in nature. In the mid 18th century, the practice became widespread, especially among the large international community of artists working in Italy.
By the 19th century it had become a normal part of artistic training, and for the next fifty years or more almost every landscape painter in Europe, whether travelling in Italy or working at home, made these simple direct oil studies in the open air. Conceived purely as studies or exercises, the sketches were rarely meant to leave the studio or be seen by a public audience.