The Lindemann brothers’ glass

At this year’s Cheltenham Science Festival Mark Lythgoe and his students made the deliberately provocative suggestion that medical images have had a greater impact on the imagination than any work of an artist. The first image was something of a slam-dunk for their argument: the radiograph taken by Wilhelm Konrad Röntgen of his wife’s hand, taken three days before Christmas in 1895. In less than five years x-rays went from being a weird curiosity that shook physics to a must-have medical and photographic tool that transformed how we look at our bodies. By 1905 there were several commercial manufacturers making tubes for medical imaging and home photography.

The penetrating power of the x-rays emanating from these tubes varied and the factors affecting it seemed myriad – the size of the induction coil, the type of interruptor (the x-rays were pulsed to build up more voltage in the coil), the quality of the vacuum, the quality and age of the electrodes, and the thickness of the glass, among others. The best images were obtained with x-rays of intermediate ‘hardness’. Several scales of this hardness emerged, including Bernhard Walther’s eight-point W-scale based on the ability of the x-rays to cause fluorescence on a screen after passage through platinum foils of different thicknesses. Such semi-quantitative measurements made it possible to surmise that the glass of the x-ray tube might itself be a hindrance to producing images.