Why do mirrors not follow brewster's angle? Normally a material will have an angle where the reflected light is completely polarized. Now say we have a mirror (implemented by a conductive silver coating) that reflects most of it's incident light. https://physics.stackexchange.com/a/10925 says that this imperfect mirror will be mostly linearly polarized, but not at the brewster angle. Why is this? The derivation for the brewster angle assumes non-magnetic materials, but does not assume non-conductive materials I believe.
 A: I think you may have misunderstood the answer to the question you cited.  It says that light reflected from a silvered mirror will be mostly unpolarized.  This is true whether the silver is on the front or back surface.  There is a very slight polarization due to the less than ideal properties of the silver.
The front surface of a back-surface silvered mirror will reflect highly polarized light, but whatever gets past the front surface will be almost perfectly reflected by the silvered back surface.
A: Brewster's angle relates the index of refraction to a polarization phenomenon
in reflection from a dielectric (insulator) material.   Most mirrors are
silvered (have a metal coating), and the equivalent dialectric constant
for a metal is ... infinity.   That predicts a Brewster's angle
of 90 degrees, which is geometrically unavailable to an experimenter.
$$ \Theta_{B}  = arctan({\eta_{metal} \over {\eta_{air}}})  = arctan({{\infty} \over 1})$$
The ninety degree angle is simply not a glancing incidence possibility for
a reflection to be observed.   It is not incorrect to say that metallized
mirrors DO follow Brewster's angle.
