Since the practice turn, the role technologies play in the production of scientific knowledge has become a prominent topic in science studies. Much existing scholarship, however, either limits technology to merely mechanical instrumentation or uses the term for a wide variety of items. This article argues that technologies in scientific practice can be understood as a result of past scientific knowledge becoming sedimented in materials, like model organisms, synthetic reagents or mechanical instruments, through the routine use of these materials in subsequent research practice. The proposed theoretical interpretation of technology is examined through a case where a model organism—Drosophila melanogaster—acted as a technology for investigating a contested biological effect of a mechanical instrument: Hermann J. Muller’s experiments on X-ray mutagenicity in the 1920s. The article reconstructs how Muller employed two syntheticDrosophilastocks as tests for measuring X-rays’ capacity to cause genetic aberration. It argues that past scientific knowledge sedimented in theDrosophilastocks influenced Muller’s perception of X-ray-induced mutation. It further describes how Muller’s concept of X-ray mutagenicity sedimented through the adoption of X-ray machines as a ready-made resource for producing mutants by other geneticists, for instance George Beadle and Edward Tatum in their experiments onNeurospora crassa, despite ongoing disputes surrounding Muller’s conclusions. Technological sedimentation is proposed as a potential explanation why sedimentation and disputation may often coexist in the history of science.