Seventeenth-century painters were masters at painting objects and beings that seem tangible. Most elaborate was painting translucent materials like skins and pulp: human flesh and grapes, for instance, require various surface effects and suggest the presence of mass below the upper layers. Thus, the viewer is more or less convinced that a volume or object is present in an illusionary space. In Dutch, the word ‘stofuitdrukking’ is used: expression or indication of material, perhaps better understood as rendering of material. In English, ‘material depiction’ probably captures this painterly means best: it includes rendering of surface effects, while revealing the underlying substance, and it implies that weight and mass are suggested. Simple strokes of paint add up to materials and things that are convincingly percieved. At first glance, material depiction hardly seems a topic in early-modern art theory, yet 17th-century painters are virtually unequalled as regards this elaborate skill. Therefore, 17th-century written sources were studied to define how these might discuss material depiction, if not distinctly. This study concerns one of many questions regarding the incredible convincingness of 17th-century material depiction: besides wondering why the illusions work (Di Cicco et al., this issue) and how these were achieved (Wiersma, in press), the question should be asked why this convincingness was sought after. Was it mere display of ability and skill? And how was material depiction perceived, valued and enjoyed? First, contemporary terminology is determined: the seemingly generic term ‘colouring’ signified the application of convincing material depiction especially — which is not as self-evident as it sounds. Second, and extensively, the reader will find that convincing or appealing material depiction was considered a reference to religion and natural philosophy.