This paper is concerned with forms of writing that characterize the laboratory, a research place where scientific knowledge is made to emerge and can be grasped in its emergence. Laboratory notebooks and other forms of research inscriptions have received increasing attention in recent years. With few exceptions, however, the epistemic function of such notes in the overall order of knowledge production has been widely neglected. This paper tries to compensate for this neglect. It highlights some facets of the productive function of particular forms of laboratory writing in the process of knowledge acquisition. In other words, it considers laboratory writing in its epistemic positivity. The first part describes some characteristics of individual, primary laboratory 'write-ups.' As an example, a short case study on the research notes of the German geneticist Carl Correns follows. The paper closes with a few remarks on collective forms of laboratory writing.