How so? Is it because it's dirty?

it's not dirty...thats phosphorus thats still in the lamp after i filled it with water.

I've done that before!

How did it get filled with water? I don't see water damage, looks like you stratched it all up with a broken piece inside.

well it wasn't a piece of glass,the lamp was in a recessed square fixture,the socket was loosely held in (a Deoderant Cap with metal pieces for contact XD) the end of the lamp was supported by a screw in the end of the fixture that was quite sharp on the end....the fixture fell and the screw punctured the dimple at the end of the lamp...then i tried to make it clear by filling it with water may not be visable in the pic but the frame actually developed some corossion from the water...meh

And it STILL works?!

for a while it did....then i dropped the lamp and broke the glass,arctube survived and i ran it a couple of times all by itself under some heavy glass and even submerged in a glass gar full of water....bad bad experiments,nothing went wrong but dangerous still.

I thought once the seal was broken, the lamp wouldn't work.

@streetlight 98: yes some lamps have an auto-extinguish feature that makes them safer if the outer bulb is broken

yeah some lamps have that...the best example i remember is the Durotest Safe-T lamps which i believe used a thin carbon strip that would vaporize in the presence of oxygen...im sure some other Mfg's made these type lamps but i can't recall any off hand.

in the case of a lamp like this it would continue to burn until the seals oxidized.