Hazy Spots on Photographic Plates

In this article, different experimental attempts to measure the velocity-dependency of the electron’s mass will be discussed. These experiments were carried out between 1901 and 1916 by Walter Kaufmann, Alfred Bucherer, Günther Neumann, and Charles-Eugène Guye together with Charles Lavanchy. They all attempted to capture this effect on photographic plates, such that it could then be measured afterward as precisely as the plates allowed for. It will be argued that two different approaches to the production of precise photographic plates can be distinguished: one that conceptualized precision in terms of qualitative plates, and one that attempted to achieve it through quantity. In the final part of the article, it will then be argued that these two approaches were shaped both by the specific radiating materials at hand as well as by the intellectual context in which the scientists involved were working.