So I went out to Spenser's on Sunday and bought two 52oz Lava Lamps. My fiance and I sat and watched for a long time as a stalagmite formed, then a while later, the infamous "spurting" event when the warm lava erupts into the still cold water like a volcano. Finally, the column breaks and collapses. On one of the lamps, I had to jiggle slightly because a massive clot of semisolid lava had formed at the top and gotten stuck there. Slowly, the movement started up in each lamp, but mainly just a couple of large blobs go up and then back down again, not the classic flow like that of my old USA 32oz Midnight Blue. So I walk to Lowe's (there's one just two blocks from my house, yay) and buy two 60 watt ceiling fan bulbs, which have the same form factor as the default 40 watt appliance bulb, and "upgrade" my lamp. I put the still-warm globes back on the bases, and a short time later, the lava has definitely got that classic flow pattern just like my USA lamp. Several hours later that night, I dropped off my fiance, came back inside, and turned both the lamps off to go to sleep. Monday morning, I turned them back on, then later in the day, I left for work (my job starts at 2:00pm FYI). The lamps were flowing nicely when I left, but when I return home from work, I was greeted by a scary sight: the entire mass of lava from both lamps is cooking at the top, and the airspace under the bottle cap was much smaller than normal. I turn off both lamps and set the globes flat on the table, but it was at least 25-30 minutes before the Lava blobs moved away from the top. I swapped the 60s with the original 40s, replaced the globes, and the many suspended lava blobs slowly began to perform their magical dance once again.
The flow has remained very nice ever since. I guess what I'm trying to say is to be patient because it can take a long time to achieve optimal flow, esp on a brand new lamp.
Oh, and be extremely cautious and make sure you absolutely know what you are doing before changing the wattage.