In pre-modern times the art of enameling, (stained) glass painting, polychromy, mosaics and oil painting all share similar optical characteristics. Artisans created translucent enamel colors on different types of metallic surfaces, enameled mosaic stones with transparent vitreous layers, made translucent stained glass windows and painted glowing glazes with oil colors. Whereas several scholars alluded to the material connections between the above-mentioned crafts, its implications for a growth of optical knowledge within the visual arts have never been explored. This paper will deal with the question of how artisanal knowledge was triggered and changed by the confrontation between and competition of diverse crafts that were optically related in the period up to 1450, finally leading to a particular and striking know-how for representing light and luster in the works of the famous Flemish painter Jan van Eyck and his contemporaries. Combining research into art technological sources, reconstructions of historical painting techniques and technical research into art objects, it will become clear how the search for lustrous effects in pre-modern crafts led to the exploration and ultimately emancipation of drying oils in the workshop of the panel painter. Finally, I will argue how the artisanal understanding of the properties of translucent and transparent materials, and the oil medium in particular, contributed to the astounding display of optical knowledge characterizing the painters of the ars nova in the fifteenth century. This way investigating the ways in which the history of image-making is intertwined with the history of knowledge-making, both in the exploration of the optical properties of materials and in the history of the imitation and representation of gems, gold and glass with oil paint, sheds new light on the early Netherlandish innovations in panel painting. While it is usually studied as a pictorial transformation, it can also be considered a material revolution, in which the art of painting lost its ties with the crafts that it was so closely connected to in the centuries before.