Gabriel Lippmann had gained credibility within the scientific community when he revealed his theory of the solar spectrum to the Academie in 1891. The spectrum provided a photographic image of an instrumentally isolated object, the sun, via a spectroscope with the ability to record the characteristic Fraunhofer black lines, familiar to astronomers. It demonstrated the full potential of instantaneous natural colour photography: a photographic process without the artifice of pigment or the intervention of colour separations. Like a daguerreotype, the Lippmann photograph had to be held in the available light at the right angle for the image of the spectrum to be visible. For a larger audience, light reflecting from the surface of the plate could reconstruct the image to project it onto a white board or screen. This projection might appear to the audience to be an aesthetically satisfying simulacrum of nature's “rainbow.” When Lippmann presented this photograph, his first claim for this invention within his paper was the provision of a photographic image that would last indefinitely; it would not fade or decay under light (Lippmann 1891, 274): “Je me suis proposé d’obtenir sur une plaque photographique l’image du spectre avec ses couleurs, de telle façon que cette image demeurât désormais fixée et pût rester exposée indéfiniment au grand jour sans s’altérer.”