A tape head cleaner cassette made of clear hard plastic. The plastic is birefringent and demonstrates internal stress as coloured patterns (photoelasticity) when photographed using cross polarisation. The polarising light source (an LCD monitor) has been rotated such that the polarising filter on the lens is oppositely oriented and so cuts out all the direct light, leaving a black background.
I hereby award Kiran Gopi the Commons Contributions Barnstar – for your tireless work regarding uploads. The community can be proud to have you as a member. -- Raghith (talk) 05:10, 26 April 2011 (UTC)