This cross, when printed in glow-in-the-dark PLA from colorFabb, has a hidden word that only shows when you hold it up to a light.  Also the glow represents grace to the holder of this cross in dark moments.  The secret word is 'JESUS" and it is written as five hollow letter-shaped chambers inside the cross.  This way when you hold it up to the light and look at the flat (bottom, or back) side of it, you see "JESUS" in lighter PLA surrounded by darker PLA.  If you print it solid or with high infill percentage, you get this effect more noticeably as well as brighter glow in the dark.  Use the ColorFabb glow-in-the-dark because the other brands (to my knowledge at this time (january 2015)) are not very bright in the dark but that stuff is really bright.  I have no affiliation with the company or its distributors.  Also charge the object in sunlight for a while to get best glow duration and brightness.  You can change the secret word in the OpenSCAD file if you like.  The secret word does not appear from the front because the digital effect and distance distort and diffuse and diminish it's light.  That way you don't see the secret word backwards on the front, only forwards on the back.  And that's about it!  Les