Last October I received a lava lamp for my birthday. It's a european model - the globe is 20cm tall and it's powered by a 30W 240V reflective light bulb in E14 R39 size.
The instructions on the box say that it works best in room temperatures of 20-25 deg. C. And last October it was working great (I can put a video on Youtube if you want). On average, about 6 blobs of wax were moving around different parts of the globe at any given time.
The thermometer on my wall was indicating a room temp. of 21 deg. C. I also managed to measure the outside temperature of the glass globe with an infrared thermometer and it was abot 54 deg. C when operating.
Now that it's December and the room temperature has fallen to 17 deg. C, the lamp seems to have trouble warming up fully. After 6 hours of running, the best it can do is produce two big blobs that make it halfway up the globe and start to fall back down, separating into smaller blobs in the process. Using the same infrared thermometer, the globe's outside temperature is now only 51 deg. C.
Is there anything I can do to make it work like it should? I've checked the bulb and the glass is still as clear as when it was new. Also, the lamp is right next to my wooden cupboard and far away from any windows or draughts. Today I tried slightly unscrewing the bulb in its holder to bring it upwards a few mm closer to the globe. Still waiting to see if it has any effect.
Lamp holder is not damaged at all - it was just getting hot enough to smell like barbequed plastic (lol). I didn't take a photo of the setup with the halogen (and now I've taken things back to normal), but let me try and describe what I did. The lamp came with a 240V E14 holder for the original E14 lamp - this is what it looked like:
MR16 bulbs look like this:
So all I did was take off the 240V wires of the old holders, and run the GU5.3 wires in their place, in such a way that the white holder was in the center of the original black holder (which I left in the lamp), and passed the white 12V wires right out of the lamp. The MR16 was thus roughly where the old lamp was. So naturally, when I switched it on, and since the dichroic reflector reflects only light - and lets heat pass straight through - the 50W filament of the halogen was right next to the tip of the original holder and the holder got hot enough to start smelling. I'm not sure what it's made of, but since it's black and brittle-looking, I'm going to guess bakelite. And bakelite is a thermosetting polymer, which means that it doesn't melt; it burns. Luckily it didn't get hot enough to burn in 3 hours, but my little white GU5.3 holder turned a dark brownish colour.
So then I just undid the modifications, put the original bulb back (which looks like this btw: )
and then I got the bottle idea with a little inspiration from my dad.
Here's a couple of pics of the running lamp with the bottle. The lamp tends to overheat when I leave the bottle on it (I measured a peak temp of 60 deg. C on the glass), so I alternate between putting the bottle on and taking it off depending on what the lamp is telling me. In the pics it had been running for 7 hours, but it cooled down to below optimum because I removed the bottle (so basically you can see the original problem)...
With bottle, a few seconds later:
The bottle itself showing the cut-out at the bottom:
My toasted MR16 holder and bulb after the failed experiment (notice the brown colour of the holder compared to the whiteness of the wires):
Finally - 2 pics of the lamp at almost the right temperature after running for only 10 minutes under the bottle (i.e. 10 mins after I took the first pic in this post):
P.S. I'm using the diagrams on this page to gauge the temperature based on what the blobs are doing: http://www.lavalamp.com/resources/use-and-care/
In future, I want to get a straighter, plainer looking bottle to cover it with (the funny looking bottle is the only empty one I had at the moment. It's for a popular brand of mineral water in Malta). Possibly I might also get a plug-in dimmer to make it run perfectly with the bottle on without having to remove the bottle every half hour.