The vivid green color of copper(II) acetate made this form of verdigris a much used pigment. Until the 19th century, verdigris was the most vibrant green pigment available and was frequently used in painting. Verdigris is lightfast in oil paint, as numerous examples of 15th-century paintings show. However, its lightfastness and air resistance are very low in other media. Copper resinate, made from verdigris by boiling it in a resin, is not lightfast, even in oil paint. In the presence of light and air, green copper resinate becomes stable brown copper oxide.