Century Base not heating up enough?

[amy m]

Hi everybody. I bought a century base off ebay for an extra 52 oz. bottle that was homeless. When I put in on the Century base, the lava won't flow. After 4 hours it's still just kind of a halfway melted lump at the bottom. It came with a bulb that looked really old, so I changed out the bulb to a new clear 40 watt bulb. Still the same result. The lava flows great when I switch it back to a newer lava world base. Am I just not waiting long enough? This is the first vintage base I've ever used so I wasn't sure if this is normal. Thanks!