In response to an innocent question about what the fake coal in living room gas fires is made of, I received this delightfully convoluted quote (thanks, Miss Foottit)...
"A gas fire with coal effect has a gas manifold or box divided into separate gas compartments with gas outlets therefrom and is formed with illumination apertures. The coal effect which is ceramic and has flame apertures therethrough is precisely positioned on the gas manifold or box by locating formation so that the gas outlets and flame apertures are correctly relatively disposed to avoid "sooting".
An electric lamp (preferably two) is disposed forwardly and downwardly of, and preferably centrally of, the gas manifold or box and the coal effect to provide an instantaneous "glow" effect when illuminated. This latter effect can be attained with or without flames being present."
