When I put the light out in the shed a circlular glow emanated from the roll of plastic that I use for 3D printing This the first time I have seen this and to all intends its a standard roll of PLA polylactic acid (Poly or polylactic acid or polylactide is a biodegradable and bioactive thermoplastic aliphatic polyester derived from renewable resources, such as corn starch, cassava roots, chips or starch, or sugarcane. In 2010, PLA had the second highest consumption volume of any bioplastic of the world
From https://en.wikipedia.org/wiki/Polylactic_acid
Having look at the web is quite common to have a glow PLA
Derek's dabblings 