Very nice question!

Let's look at the frequency distribution of a halogen lamp:

[![enter image description here][1]][1]

You can see that all frequencies are present (hence the white color). The temperature of the burning lamp is about $800$ Kelvin. If you polarize the beam nothing, in particular, should happen because the photons have a random distribution of polarization. The intensity should obviously get less (with a polarization filter).  
Did you change the settings of the camera? I think you have to (why did you use two filters, by the way?).

I can think of nothing else to conclude that the metal reflects the light in such a way to produce your observation(s). Paper reflects in a completely different manner. Try using another metal.




  [1]: https://i.sstatic.net/uDBSz.png
  [2]: https://www.researchgate.net/post/How_can_I_obtain_a_circular_polarized_light_with_Tungsten_Halogen_light