Lava Lamp Scientists

Comment

Comment by João Roberto Gabbardo on April 25, 2010 at 7:03pm

Well, according to your experiments the material of the coil (or the object) placed in the bottom of lava lamp plays important role to break the ooze surface tension. The 2 coils I have are stainless steel made and this material probably was chosen due to be corrosion resistant (by first?) and for the propriety of break the ooze surface tension. The metallic paper clips are mainly made by galvanized steel. I’ sure you know how that the proposal of galvanization process is protect steel from oxidation by means of covering it with a fine zinc layer. So an interesting question arises: is the zinc better than the stainless steel or even the steel to break the ooze surface tension? I know the problems involved to heating using induction coils and I was just thinking in an alternative way – not the most efficient – of heat the lamp. Too much difficulties (and high cost) are involved to use it in lava lamp and it was a simply crazy suggestion of me. On the other hand if one wants uses heating by resistance instead of incandescent lights the best way of provide the illumination is using LEDs. Today we can found high power LEDs with efficiency higher than fluorescent lights making them very attractive to make experiments. Of course I agree with you that the use of incandescent lamps offers a very good cost-benefit to regular experimentation.
Concerning to your second message the shape of the lava lamp recipient is very important. The short recipients don’t provide sufficient temperature gradient and not allowing the ooze circulates properly. The heating is also a problem and an adjusting heat source is mandatory. Here is one drawback of use incandescent lamps to heat and illuminate at same time: you only reduces the heating as expense of reducing the light intensity. So tacking this problem in account seems to be attractive use independent sources of heat/light.

Best regards,

João Roberto Gabbardo

Comment by MagicLamp on April 12, 2010 at 7:30am

Also, I meant that when the lamp overheats and the temperature is pretty much uniform everywhere, there are no more gradients that could make the blobs move, that's why they wax usually collects on top after protracted operation, even in otherwise carefully balanced lamps, even commercial-grade ones: unless the shape of the globe and the lamp's power are calibrated as to ensure that there will always be a large enough temperature gradient across a wide range of temperatures (which is just impossible without an adjustable power heat source and/or a variable cooling lamp top), the lamp will "stall" at some point and you will have to power it off.

Comment by MagicLamp on April 12, 2010 at 2:36am

I should rephrase my statement in clearer wording: the coil does play an important role in breaking the surface tension, but it does not do so by concentrating heat, and it has no significant heat localization effect whatsoever. It works purely by mechanical action. A coil-less lamp would result in one big blob that seldom breaks and seldom reconnects and would be, overall, pretty boring to watch.

During my own experiments, I found out that using too soft materials for the coil, like e.g. copper wire or metal dish brush filaments, didn't result in proper breaking of blobs (even though they would concentrate more heat than a polished stainless steel coil, due to them being darker and less reflective): the blobs just pushed the metal aside without breaking.

However even by using some paper clips joined in a girdle or a coil of 1mm solder wire, resulted in immediate breakage upon contact, even when the coil was mostly "submerged" in wax.

As for the other concept, an induction-heated lava lamp, it would sure be possible if you got a suitable coil inside it, the only problem would be that such a coil would be very visible and much bulkier than the simple tension-breaking coils. It would have to be made of proper, corrosion-resistant materials, and also have constant heating/resistance properties over time.

The lamp mechanism would have to be replaced with a powered "emitter" induction coil, and that coil would have to be as close as possible to the one inside the lamp (the "receiver") in order to avoid losses, and you would also have to provide separate lighting through something small and powerful enough to fit between the two coils without emitting too much (or any) heat itself (LEDs?).

The main problem would be power efficiency (power would be lost the farthest the two coils are, and some minimum distance is inevitable. It's one thing using an inductive charger for something that uses 3-5 W (like e.g. a rechargeable toothbrush or computer mouse) and for something in the 40-50W range, plus having to provide for separate lightning.

Lava Lamps are one of those applications where incandescent lamps provide the ideal mix of heat and light in one device: no reason to make it any more complex just for the sake of it ;-)

Comment by João Roberto Gabbardo on April 10, 2010 at 4:08pm

When I was making experiments with my damaged lamp I noticed one of the effects you are describing: the ozze was accumulated in the top and from time to time a big blob (due to the cooling of part of accumulated ooze) was falling. This problem was caused by an incorrect density balance between the ooze and water not by overheating: the lamp has a dimmer and was possible control the heating and was impossible make the lamp works properly adjusting the heating, either the ooze stays at the bottom or was accumulating in the top.

Of course the coil is not responsible by itself to break the blobs, the heat also takes a important place in the game and again I was able to notice it in my experiments. When the rising (and hot) blobs touched the ooze in the top (more cooled) they didn’t joined to it immediately, only after transfer sufficient heat to disrupt the contact surface between them.

So we agree in the point when the coil is completely covered by ooze: it doesn’t play an important role in the surface tension breaking mechanism, here the heating makes the hard job.

You are sure. Place one black disk inside the bottle is not worthwhile. One interesting idea is use the same principle of induction owens. I think you know a kind of electric owens without heating resistances where the pans are placed directly over the ‘heating plate’ and the pans heat the food like a magic. Of course there are no magic in the process, the pans must be metallic made and below the heating plate are coils where a strong alternating current with high frequency flows creating a intense alternating magnetic field. This field induces closed current loops in the bottom of the pans and the heating is produced by resistance loss in the metal. The same phenomena takes place in the iron core of transformers and the current lops are also called ‘eddy currents’ or ‘Foucault currents’. The cores of transformers (also the stator and rotor in the motors) are laminated just to reduce the losses by these current loops. Why not try to use the same principle with lava lamps heating the lava directly by the coil in the same way of induction owens? The lamp should be replaced by LEDs and even the LEDs who change the color automatically could be used creating interesting light effects. This is only a suggestion, after all the efficiency of such arrangement can be lower than use a incandescent lamp!

Comment by MagicLamp on April 5, 2010 at 11:26am

Well, the ooze is much softer than the coil and touching it disrupts the blobs' surface. If there was just enough wax for one blob in the whole lamp, then yeah, a coil wouldn't be necessary: the same blob would keep going up and down due to heat gradients. If you have multiple blobs though, when you have a malfunctioning coil (e.g. too thick, too porous, too dirty) then they tend to stay separated, like many baloons, and don't recombine.

Consider e.g. what happens at the top of the lamp, where blobs touch for long times but very seldom break up and mix (only if the lamp overheats they connect away from the coil) or what happens to "in flight" blobs that touch: they just bounce off each other.

By the time the lamp heats up enough as a whole to start the cycle, the coil can't make any difference (and for that matter, it can't be hotter than its surroundings: its temperature will be dominated by the fluid and wax around it). Now, if you had a charcoal black disk directly facing the lightbulb, even several centimeters inside the bottle...then yeah, that would localize some extra heat due to irradiation, but still no big deal.

Comment by João Roberto Gabbardo on April 4, 2010 at 5:31pm

I must admit that my experience with lava lamps is very little; after all I only had one lava lamp! In spite of it worked well, the clear liquid was clouded. Probably the lamp was packaged warm and immediately shipped. I made several experiences intending to repair the lamp (but letting the original ooze) and discovered that if you shake the lamp when it is warm the ooze mix with the water at some extent clouding it. In my thoughts the coil seems to spread the heat in ooze like the heatsinks used in electronic components.
If you consider a lava lamp operating in such way like ever having enough quantity of ooze in the bottom to let the coil completely covered, how it will act to break the ooze surface tension? In this situation the blobs will emerge due to the heating from the top of the accumulated ooze or a quantity of ooze is splashed forming a blob when one cool blob falls in the accumulated ooze.
Anyway the metallic coil is better to transfer the heat to the ooze than the glass but as you pointed, due to its low size and mass how much it takes part in the working of the lamp?
I think that if the ooze was heated directly by the coil it would be work in the same way but with a increasing of the energy efficiency. In the actual lamps the incandescent light bulb serves to furnish heat and light with low efficiency since the heating happens mainly by radiated heat. Using an element like the coil to directly heat the fluids will save energy and would allows use LEDs as light sources that are much more efficient than incandescent lamps.

Best regards,

João Roberto Gabbardo

Comment by MagicLamp on April 4, 2010 at 4:32pm

I don't know if the coil has -or even if it's supposed to have- any serious effect on spreading the heat: after all, it has too small a mass, too little surface area and total thermal capacity compared to the fluid, wax and even the glass surrounding it.

I know it has an important role in breaking up the surface tension of the blobs though: the soft copper and dish-scrubbing wire mesh just let the wax "flow" through them without breaking it, and the wax kept itself in one big blob. The hard steel paper clip OTOH resulted in the wax breaking up almost immediately on contact.

Then again....it might be that due to its being metallic and closest to the lamp's filament, it might have a localized high temperature gradient (although the surrounding fluid and wax would cool it almost immediately). I wonder how a lamp where the coil was a direct heating element would perform....

Comment by João Roberto Gabbardo on April 4, 2010 at 3:44pm

I was looking again the coil from my damaged (and disassembled) lava lamp and it is made by 0.4mm diameter stainless steel. The coil serves to distribute the heat in the bottom of the bottle and stainless steel is far to be the best material to do so. The heat conductivity of stainless steel is less than copper (best) and aluminum and the main reason of use stainless steel is by its greater mechanical strength compared to the other two later materials. Copper and aluminum are too much soft and is easy to deform them permanently. On the other hand a coil made by a thin stainless steel wire is sufficient hard to be squeezed and inserted in the bottle opening and returns to the previous shape. Here in Brazil we can found thin stainless steel wire in crafts material store and I bet you can found it easily there. Make a coil using a thin stainless is very easy and you don’t need any kind of special tool: just wrap firmly the wire in a rod with the diameter you want make the coil. You can use a Philips screw driver, for example. But why a Philips screw driver? Well, if you use a regular screw driver surely you will not be able to remove the coil from it due to the flared extremity!

Best regards,

João Roberto Gabbardo

Comment by Jennifer on April 4, 2010 at 1:47pm

Wow, great idea! I have found springs at my local Ace hardware, but they are so stiff and thick that I have to get my husband to fix them for me and then still, he usually scrapes up his fingers.
Thanks!

Comment by MagicLamp on April 4, 2010 at 1:46pm

About the wax I used: I found it best to use high-quality candles with all-solid color wax. They cost more, but they are worth it, for they have great opaqueness and color consistency compared to white waxes with just external color coatings. The black wax comes from such candles. It occasionally shows bubbles or some blobs get too transparent, but otherwise it has a near pro-grade opaqueness. I will post the candle brand if I find it. They were quite expensive though, like 3 Euro for just two candles, enough for 1 lamp.

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