The now widely available 3D-printing technology enables structural molecular biologists to easily produce tangible models of large and complex molecules, which can aid them in understanding their spatial structure. Those models, however, are static and often monochrome, therefore their information content cannot compete with existing screenbased visualization solutions. Following the paradigm of spatial augmented reality, we present an approach to dynamically visualize molecular properties directly on the surface of 3D-printed tangible models, using a digital projector. We developed a prototype system consisting of hardware and software, that enables the tracking of the tangible model and the rendering of colorcoded molecular properties, which are then projected onto the tangible surface. Using knowledge about the geometry of the molecular model, the optical properties of the digital projector and the exact spatial relation between projector and model, the rendered projections are updated in real-time, such that they stay registered with the tangible model during user interaction. We evaluated the usability and potential applicability of the developed system by collecting feedback from domain experts from the fields of biochemistry and molecular biology.