Mathmos metallics - what bulb?

[alan lovedog]

Managed to find a metallic gold mathmos atro at a boot sale last week - great. Only thing is, with the regular astro bulb the liquid starts to rise but can't break off - it just pulsates at the bottom. Now maybe it's just because it's really old and essentially dead, but maybe it needs another bulb strength? Anyone have any thoughts? Thanks in advance