Lippmann made use of this phenomenon by projecting an image onto a special photographic plate capable of recording detail smaller than the wavelengths of visible light. The light passed through the supporting glass sheet into a very thin and nearly transparent photographic emulsion containing sub microscopically small silver halide grains. A temporary mirror of liquid mercury in intimate contact with the emulsion reflected the light back through it, creating standing waves whose nodes had little effect while their antinodes created a latent image. After development, the result was a structure of lamellae, a very fine fringe pattern in distinct parallel layers composed of submicroscopic metallic silver grains, which was a permanent record of the standing waves. Throughout the emulsion, the spacing of the lamellae corresponded to the half-wavelengths of the light photographed; λ/(2n), λ being the wavelength of light in air and n is the refractive index of the emulsion. Thus colour information was stored locally. The larger the separation between the fringes, the longer was the wavelength recorded from the image colour, red being the longest.