The bright glow is caused by the phosphorus coating on the tritium vial being energised by UV light.
I present version 3A of my small keychain tritium lantern for use with a 2x8mm tritium vial (tritium vial not included).
The attachment hole is 2mm wide and is perfect for a 10mm split ring (not included).
The tritium vial should be set using a UV activated optically clear adhesive such as Norland 61 or Loctite glass bond. These adhesives will cure in direct sunlight in an hour or so.
There are some more photos of this object and other examples of my work, both 3D printed and otherwise, on my 'Tofty' facebook page
0.53 w x
1.424 d x
0.209 w x
0.561 d x