A few years ago I had a fantastic old sculpture workshop in a falling-apart Newtown terrace. There was a lot of space for strange experiments, including this technique for making gigantic lava lamps out of supermarket ingredients. These ones aren’t quite as active as the ones you can buy in shops, but they have their own leisurely charm… And they’re giant! 
Lava liquids in action.
So, here’s the recipe.
How to make a lava lamp (the home-cookin way)
The container has to be fairly large for one of these lava lamps. Try about 10 litres at the minimum… Discount stores have massive glass vases for around $30, and they make great containers. It’s already closed at the bottom, so no chance of leakage, and then you just need to find something chemically inert to close the top with. Aluminium is ok, but it will react with the water over time and form that white crusty oxide. Glass is best! Stainless steel is ok, or some sort of plastic that won’t react with ethanol. (NOT perspex! It makes the worst smell in the universe: like sticking your head in one of those nail polish parlours and inhaling deep. TOXic.) I seal them with regular household silicon sealant, and this doesn’t seem to react with anything. There also needs to be an air space at the top, of about five centimetres or so. Air expands and compresses a lot more easily than water; and as the liquids heat up and expand the air at the top absorbs the pressure increase within the sealed container.
Then the base needs to be sturdy and tall enough to hold the light bulb — about 14 cm is usually heaps for a vertical socket, screwed to the bottom, plus the 100W incandescent bulb.
The Liquid
The density of the liquid needs to be only just barely less than the oil. This way as soon as the oil heats up it expands, and thus becomes less dense, and so it is then lighter than the liquid; it floats to the top and then cools down and sinks and the cycle continues.
This method uses methylated spirits (a cheap and easy way to buy ethanol) as the liquid. Because its lighter than water, the oil will actually sink in the metho. The trick is to dilute the ethanol with water, making it slightly heavier, until the oil is just about to float — at this point the oil at the base of the container seems ’springy’ and joyful and bouncy, just ready to leap off the bottom. (This comes later.)
So, start with a few big containers of metho and pour them into the clean container. To dilute it add just a little distilled water and mix them together: say, about half a litre to every 10 litres of metho. At this point the liquid should still be a bit lighter than the oil, so that the oil stays safely on the bottom while you are adjusting the density balances. It’s best to put the liquid in first and then add the oil: the plan is to disturb the oil as little as possible in the entire process, otherwise it’ll break up into lots of small bubbles and will take forever to join up again, if it ever does.
An easy way to tint the liquid is food colouring.
The Lava
This is made of baby oil! Simple! It’s basically mineral oil, which has a specific gravity very close the ethanol so they’re pretty close in density from the start. One addition is vaseline. The oil by itself forms bubbles inside the liquid that float around and bounce off each other in a boring kind of way, and they are slow to join up again when they get to the bottom, and they often don’t stick to the metal coil (later). So a little vaseline, added in a proportion of about 1:5, makes the oil good and sticky. This has to be something to do with surface tension but I don’t really understand how it works. Oh yeah, the vaseline also makes the bubbles themselves more dynamic, less bound to a spherical shape when moving around.
Get an old saucepan and melt the vaseline into the baby oil on low heat, without letting it burn. Then wait for it to completely cool before adding it to the liquid or else it’ll be heated and thus just float to the top and be annoying. Refrigerate it if you’re in a hurry but not so that it solidifies.
Oil and vaseline mix is a really groovy stuff. It’s a mix of two different consistencies, and the oil is suspended into the vaseline so their consistency ends up being somewhere in between, but they still separate out over time. It’s beautiful luscious stuff.
A good way to colour the oil is with candle tint — I get it from Stacks of Wax in Newtown. The tint has to be oil-soluble, and that’s hard to find! Oil paints are made of a powder suspended in oil and that won’t work, as it just sinks to the bottom and looks really crusty and dodgy. I’ve heard that a chopped-up Sharpie marker will work, but when I was doing this they weren’t available in Australia. So I wasted money on a lot of markers, none of which worked… The candle tint comes dissolved in a wax lump, and it does have a whole load of goop in it, and the colour isn’t pure, and some of it dissolves out and colours the liquid itself (because some of the ingredients are water-soluble instead…). Drop a bit of the candle tint into the saucepan of lava and melt it through, remembering that it’s a very intense dye — you don’t need much.
The Coil
There has to be a metal coil at the base too — the lava to sticks to it, making it stay at the bottom and really soak up the heat. Without it the lava quickly reaches an equilibrium in the liquid where it just floats near the bottom without any action at all. This coil needs to be totally rust-free, and I use titanium from a jewellers’ supplier, it’s quite cheap! Coffee plungers from op shops have a coil of exactly the right size and shape attached to the metal sieve of the plunger part, so that’ll show you the rough idea. Ssince they’re stainless steel they might even work, but I’ve never tried one.
The Combining
This is the tricky part. First things first.
It’s a really good idea to test the balances before you charge ahead. Get a glass jar and scoop up the liquid in it. Now, take a tiny bit of the lava mix and drop it into the jar. This’ll let you know where their respective densities are at: if the liquid is too heavy the oil will float; if it’s too light the oil will plummet like a stone to the bottom. If it’s just right the little bubble of oil is going to gracefully and unhurriedly float slowly but surely downwards and then bounce a little at the bottom before coming to rest. Shake the jar and it should leap about then settle again slowly.
Here’s the thing: If you add the oil to the final container and it floats, then you are going to have to lighten the liquid to compensate; this means pouring a batch of lighter liquid through the layer of oil into the metho mix underneath, and the oil is going to break up into a shower of tiny droplets all mixed through the liquid and it’ll take forever to settle out again, and you don’t want that. With the oil safely at the bottom you can very gradually and carefully raise the lightness of the liquid until it’s just right.
What I do is get a large funnel with a tube coming off the bottom that reaches to just above the base of the container. Rest the funnel on the top lip of the container and slowly pour in the lava gloop. Try to match the rate of flow through the tube so there’s a consistent pour without any air bubbles. If it’s going well you’ll see the lava pool at the bottom, but it will be slooshing around and bouncing into the liquid as it keeps coming through.
Now it’s ready to test. Put a light bulb underneath it — either the finished base or some tester device that can support the container with a bulb underneath — and turn it on. These ones take only a few minutes to get some action going, and what you’re looking for is continual movement up and down and through the container. It’s exciting to see it going for the first time.
The Adjusting
Suppose your oil is a little too heavy: it’ll just sit there, and maybe bulge a little when the heat is on, but no movement and no bubbles bouncing around. You need to dilute the ethanol with more distilled water. This has to be done delicately. If you just pour in a glass of water, the heavier liquid will plunge straight to the bottom of the container without mixing and crash into the oil, which is actually lighter than it, so the oil will splash around too, and the water will settle at the bottom with the oil between it and the rest of the ethanol mix — this is the Worst Case Scenario. Good luck getting the two layers of liquid to mix, with the oil in between them.
Thus it’s better to mix up a separate batch of liquid for diluting with. Something like half ethanol and water is good. Then pour it in a small amount at a time, mixing it in with a stirring rod, so that it’s evenly distributed. Make sure you don’t go too far or the oil will lift off the bottom and float at the top. I made a stirrer out of a length of wire twisted into a loop at the end; this also let me lift up a small bubble of oil so I could see how quickly it sank in the liquid. If your oil drifts down like a feather, it’s just right! You can also use the stirrer to make a small whirlpool effect, and this gets some of the oil to spring up in the centre and again you can observe it’s bubbliness and falling speed.
Once you’ve made the adjustments the best final way to get it all mixed up is to run the lava lamp for a couple of hours! Convection will blend together any layers of slightly lighter liquid anywhere, and after it’s run and cooled down again you’ll find it runs slightly differently the next time it starts up. The chemicals even seem to ‘cook’ together for the first few runs. This means it’s a few days of testing before you’ll know whether it’s ready.
Looking great: the balance is pretty right here.
Gratuitous workshop closeup
