I think the fact you can the see the possible outline of a coil and possibly fins shows a difference in visible//translucent light radiation in those areas.
I also find quite a bit of research on translucent sintered alumina and its ability to scatter light through rayleigh and mie scattering. Sintered alumina can appear translucent yellow depending upon how it is sintered. http://infoscience.epfl.ch/record/175704/files/NanoporeCharacterizationAndOpticalModelingOfTransparentPolycrystallineAlumina.pdf http://repository.tudelft.nl/assets/uuid:ad82e9ad-f44f-41d6-86eb-8e64d2e0086b/MS-21.908.pdf Whether this has any bearing on visible color @ high temp in the photos I am not sure. Somebody needs to heat some! Stewart On Sun, Oct 19, 2014 at 5:49 PM, Jed Rothwell <[email protected]> wrote: > H Veeder <[email protected]> wrote: > > >> Consider the difference between the sun at noon and the sun at dawn/dusk. >> The interior of the HotCat glows white but from the outside it glows red >> like a sunrise because it is shinning through an atmosphere of alumina. >> > > It does not work that way. If the outside surface temperature really is > 1400 deg C, then the outside surface material should be incandescent white. > It does not matter what the inside temperature is. All materials glow with > the same incandescent color at a given temperature. That is what the > textbooks claim. > > I doubt any light is shining through the alumina, but even if it is, the > light from incandescence of the outside alumina material itself should be > white. > > - Jed > >
