Clear vs frosted bulb

[perishingtardis]

Hi all,

I recently had to replace the bulb in my Mathmos Astro Baby. It takes a 30 watt reflector bulb. The original bulb from Mathmos was frosted, and I got a new one from ASDA but it is clear.

I didn't think this should make any difference to the flow of the lamp, but I have noticed that after about 5 hours of operation there starts to be dozens and dozens of tiny pea-sized blobs of lava floating around, so it seems to be getting a bit too warm.

Do you think this could be due to the bulb being clear rather than frosted? Has anyone experienced the same problem with clear bulbs?

Many thanks.

[Peter Panussi]

Well, I didn't notice an effect of frosted vs clear bulbs, but maybe only cause I never checked it systematically.

But I noticed dramatic effects caused by even slight differences in room temperature. In other words: My experiences show that the flow of lava lamps can be very, very heat sensitive. So I think your assumption is at least plausible.

[Callum Carr]

It could also be down to your frosted bulb being a filament bulb and the replacement being halogen?

I usually buy slightly lower power halogens for my lamps as they are more efficient and create more heat and light despite using the same amount of power.

The boxes for them sometimes have a wattage on them as well as a wattage which it is equivalent to in filament form.

E.g. a 28w halogen bulb might be equivelent to a 35w filament bulb. 

[perishingtardis]

Thanks for the replies guys. The temperature in my room has been pretty constant before and after the change of bulb (I actually have a digital thermometer in my room for the precise purpose of knowing whether it's too hot/cold for my lamps to run properly ). As far as I can tell both the frosted and clear bulbs I've used are ordinary filament bulbs - not halogens.

I have ordered some frosted bulbs from eBay - we'll see how they compare!

[Laurie]

I'm reading this in 2021... I always had frosted bulbs a few years ago I replaced with clear.. I could tell it was hotter, now it's, making a lot of bubbles. I was told to try a dimmer, I don't have yet, maybe a new base. It's over 23 years old but it runs like it's 8 years old.

[perishingtardis]

Hi Laurie in 2021! Looks like it's 4 years to the day since I made this thread.

What I've found over the past few years is that bulbs vary between brands anyway, i.e., a 30W bulb from one company could be hotter than a 30W bulb from another company. And unfortunately, lava lamps are very sensitive to small differences in the temperature. Now I use plug-in dimmers for all my lamps. It's the only way really to get them to function nicely.

Laurie said:

I'm reading this in 2021... I always had frosted bulbs a few years ago I replaced with clear.. I could tell it was hotter, now it's, making a lot of bubbles. I was told to try a dimmer, I don't have yet, maybe a new base. It's over 23 years old but it runs like it's 8 years old.

[andy ross]

I've found that if you use the premium branded bulbs you generally get a better, more reliable result, although some serious collectors look to economise on these vital items. 

Crompton and Bell in the UK are pretty good in my experience.

The only difference I can find between clear and frosted is that brilliance is diffused by the frosting, so frosted is easier on the eye if the bulb has to be visible