Busch felt his painting skills could not compete with those of the Dutch masters. He regarded few of his paintings as finished, often stacking them one on top of the other in damp corners of his studio, where they stuck together. If the pile of paintings became too high, he burnt some in his garden. Since only a few remaining paintings are dated, categorizing them is difficult. His doubts regarding his skills are expressed in his choice of materials. His ground was usually chosen carelessly. Sometimes he used uneven cardboard or poorly-prepared spruce-wood boards. One exception is a portrait of Johanna Kessler, on a canvas support measuring by , one of his largest paintings. Most of his works, even landscapes, are small. As Busch used poor grounds and colours, most are heavily darkened and have an almost monochrome effect.