Lava not moving...

[supersezzie]

Hi everyone...sorry this is probably the same question you get all the time!

I recently bought a lava lamp at a car boot sale, apparently new but obviously I don't know the history! It looked in good condition though and the liquids not cloudy or anything. Oh, and it's a Mathmos one.

Anyway, yesterday I had it running for several hours and all that happened was the lave flowed straight to the top and stayed there - it looked like it had completely solidified. Now today the wax fell to the bottom in a solid lump and formed a stalactite whilst heating up, so I thought it might work this time, but it seems that some has risen to the stop and stayed there, though it doesn't look so solid this time, and the rest is in a mound at the bottom looking like it's trying to rise but isn't. Any tips? Thank you! :)

[Ford Prefect - NPNG]

what bulb does it have in it?