What surface did artist paint on in northern Europe during the 1400?

During the 1400s in Northern Europe, artists primarily painted on wooden panels, often made from oak or poplar. These panels were typically prepared with a layer of gesso to create a smooth surface for painting. The use of oil paints became increasingly popular during this period, allowing for richer colors and more detailed textures. This technique was especially prominent in the works of artists like Jan van Eyck.