The "in situ — ex-situ" exhibition presents technological research results at i2ADS/FBAUP around photomechanical processes. Photo engraving, gillotage, photo-enamel, cromocuprography, photolithography, diazo type, lithophane, among others, were the object of technological reconstruction and its reconduct to artistic practice. The first rehearsals took place in 2016 on the pretext of analyzing a set of zinc engravings by Marques de Abreu, treated in the first seminar, “Modos de editar” . Since that date, and in transit between the observation of archives, print workshops, laboratories, offices, graphic arts companies, museums, and laboratory practice, we have reconstructed the presence, identity, and procedural visibility of these artifacts in situ and ex-situ. Along the way, we rethink how artistic research can embrace chemical printmaking in its difficult declinations, particularly in Portugal's scientific and graphic arts context. We also reveal less recognized contiguities. There, materiality proliferates, and disciplinary crossings are the basis for building the image.