Lava Lamp Scientists

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 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 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 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 Rototype on January 28, 2024 at 11:49am

It seems like quite some time has passed since the last posting in this list and I suspect quite a lot has moved on since then. With the advent of more modern technologies and easier access to complex components I can see we can have a lot of time experimenting here.

One question I have is: What is the approximate proportion of Wax (goo) to Master Fluid?

Realising now I'm sitting here that I have a) an empty AstroBaby bottle, b) a full AstroBaby bottle and c) a set of new, clean measuring jugs, I set about finding out by first marking the wax height from the full bottle to the empty one (this will probably also be useful when adding wax later) then filling the bottle with water to this line (Note: the spring was still present throughout this procedure), then pouring it out into the small measuring jug (using the small 250ml one as the measurements will be easier to get accurate). Result, about 125ml to the wax height. Next I filled up the bottle to it's 'Full' level with water, poured off into the small jug (which hasd since been emptied) to the line the water came to from the 'wax' line and the rest into the big jug. After some careful levelig of the surface it was sitting on (to get an even level in the jug), it measured out at 675ml, making the total volume 800ml.

Thus the ratio of wax to fluid is 125:675, or dividing down 5:27 (a bit over 1:5, I may have been generous with the water).

Following this if I want to fill a 700ml bottle, I should need (700/(5+27)) x 5 wax and (700/(5+27)) x 27 Master Fluid, working out at about 110ml of Wax and 590ml Fluid. Assuming 2:1 wax to Perc this gives me 73ml of Candle Wax and 37ml of Perc. Also following the vague rule of 1 teaspoon of 'salt' to 100ml water I'll probably need just under 6 teaspoons of 'salt'.

I'll probably make up the solution a bit weaker than this to start with to allow me to adjust later.

Tim

(Hereford, UK)

Next time: Mixing and filling

Comment by Rototype on February 20, 2024 at 12:39pm

So, first attempt completed and a total failure. Lovely red wax, clear(ish) fluid to start with - heated it up and absolutely no movement.

Then I decided to revisit my assumptions and calculations. Turns out the amount of Perc I'm using is WAAAYYY too much (Folks, 2:1 ain't gonna work) - looking at the numbers in a more scientific manner it's closer to 5:1, possibly 4:1 to allow for evaporation while mixing (Perc's pretty volatile).

Second lesson is the fluid went pretty cloudy with Epson Salts - I tried doubling the concentration and still no movement in the wax, the fluid just got cloudier. Next attempt will be pure glycerine added to the distilled water (Hopefully this will stay clear and be stable). 

Other factors: 1) Using the liquid colouring for the wax I bought doesn't really work too well - I ended up with a large surplus of beeswax and the liquid colour just didn't want to stick (ended up wiping most of it out of the melting vessel), concentrated wax colour chips worked well though. 2) Liquid colouring for the master fluid worked well - food colouring seemed to take pretty well but I don't know how long it will last.

Next steps: Hydrometer and measuring beakers arriving tomorrow, I want to get my numbers refined a bit more so I need to be more accurate in how much I'm putting in of each component and I want to see exactly what density the fluids are.

Tim

(Hereford, UK)

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