# Photoelasticity - TDK Head Cleaner - White background

- By: Colin
- Date: 2017-03-12
- Classification: Photograph
- Museum: [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Photoelasticity_-_TDK_Head_Cleaner_-_White_background.jpg)
- Rights: [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0)
- Picture: https://upload.wikimedia.org/wikipedia/commons/thumb/b/bb/Photoelasticity_-_TDK_Head_Cleaner_-_White_background.jpg/1920px-Photoelasticity_-_TDK_Head_Cleaner_-_White_background.jpg
- Who can see it: Tweens profiles and older (museums give no ratings; placed by Invisible Network from the museum's own words)

TDK tape head cleaner cassette "HCL-11" 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 similarly oriented and so lets through all the direct light, producing a white background.