  Several authors have claimed that the observable Hawking emission from a
microscopic black hole is significantly modified by the formation of a
photosphere or chromosphere around the black hole due to QED or QCD
interactions between the emitted particles. Analyzing these models we identify
a number of physical and geometrical effects which invalidate them. In all
cases, we find that the observational signatures of a cosmic or Galactic
background of black holes or an individual black hole remain essentially those
of the standard Hawking model, with little change to the detection probability.
