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The direct reading emission spectrometer was developed during the 1940s. By substituting photo-multiplier tubes and electronics for photographic film spectrograms, the interpretation of special lines with a densitometer was avoided. Instead, the instrument provided the desired information concerning percentage concentration of elements of interest directly on a dial. Such instruments ‘de-skill’ the job of making such measurements. They do this by encapsulating in the instrument the skills previously employed by the analyst, by ‘skilling’ the instrument. This paper presents a history of the development of the Dow Chemical/Baird Associates direct reader. This history is used to argue for a materialist conception of knowledge. The instrument is a material form of knowledge, knowledge of aspects of spectroscopy, analytical spectrochemistry, electronics, instrument design and construction, and metal production industry economics.