BUT, Jack, you should understand that you don't get any real glow this way. Cranking up luminosity a lot may illuminate the immediate surroundings somewhat, if you use high GI sample quality, 4 and above. The object is not really emmitting light, though. What you'll see on the surroundings is a GI effect.
The effect that you are looking for (probably) is a glow that surrounds the object as well. But for this, there must be something to illuminate, such as dust particles or smoke. As long as there's nothing to be lightened in the air around your object, you won't get this kind of glow effect.