What are in lava lamps?

• Fill the bottle about half full of water and add a few drops of food colouring.
• Fill the rest of the bottle with cooking oil and allow the components to settle and separate.
• Break an Alka-Seltzer tablet into quarters, and drop one piece into the bottle.
• Watch as the bottle swirls and churns like a real lava lamp!

A lava lamp is a decorative lamp, invented in 1963 by British entrepreneur Edward Craven Walker, the founder of the lighting company Mathmos.

It consists of a bolus of a special coloured wax mixture inside a glass vessel, the remainder of which contains clear or translucent liquid. The vessel is placed on a base containing an incandescent light bulb whose heat causes temporary reductions in the wax's density and the liquid's surface tension. As the warmed wax rises through the liquid, it cools, loses its buoyancy, and falls back to the bottom of the vessel in a cycle that is visually suggestive of pāhoehoe lava, hence the name. The lamps are designed in a variety of styles and colours.

Lava lamps can be associated with hippie and cannabis cultures.

A classic lava lamp contains a standard incandescent or halogen lamp which heats a tall (often tapered) glass bottle. A formula from a 1968 US patent consisted of water and a transparent, translucent, or opaque mix of mineral oil, paraffin wax, and carbon tetrachloride.p. 2, line 30 The clear water or mineral oil can optionally be coloured with translucent dyes.

Common wax has a density much lower than that of water and would float on top at any temperature. However, carbon tetrachloride is denser than water (also nonflammable and miscible with wax) and is added to the wax to make its density at room temperature slightly higher than that of the water. When heated, the wax mixture becomes less dense than the water, because it expands more than water when both are heated.p. 1, lines 40 & 45 It also becomes fluid, causing blobs of it to ascend to the top of the lamp. There, they cool, increasing their density relative to that of the water, and descend.p. 1, line 47 A metallic wire coil in the bottle's base breaks the cooled blobs' surface tension, allowing them to recombine.

Since 1970, lava lamps made for the US market have not used carbon tetrachloride, whose use was banned that year due to toxicity. Haggerty, their current manufacturer, has stated that their current formulation is a trade secret.

The underlying fluid mechanics phenomenon in lava lamps is a form of Rayleigh–Taylor instability.

The bulb is normally 25 to 40 watts. It generally takes 45–60 minutes for the wax to warm up enough to form freely rising blobs, when operating the lamp at standard room temperature, and as long as 2 to 3 hours if the room is cooler.

Once the wax is molten, the lamp should not be agitated, or the two fluids may emulsify, and the fluid surrounding the wax blobs will remain cloudy rather than clear. Some recombination will occur as part of the normal cycle of the wax in the container, but the only way to recombine all of the wax is to turn off the lamp and wait for a few hours. The wax then settles back to the bottom, forming one blob once again. Severe cases can require many heating-cooling cycles to clear.

In 2015, a new design was introduced that uses ferrofluid in place of wax.

British entrepreneur Edward Craven Walker had the idea for the lava lamp in 1963 after watching a homemade egg timer, made from a cocktail shaker filled with liquids, as it bubbled on a stovetop in a pub. He hired British inventor David George Smith to develop the device and the chemical formula it required. Smith is credited as the inventor on the original U.S. Patent 3,387,396 for a "Display Device" filed and assigned to Craven-Walker's company in 1965, and subsequently issued in 1968. Craven Walker's company, Crestworth, was based in Poole, Dorset, United Kingdom. He named the lamp "Astro" and had variations such as the "Astro Mini" and the "Astro Coach" lantern.

In 1965, Adolph Wertheimer and Hy Spector were intrigued by Walker's product when they saw it at a German trade show. They bought the American rights and began the Lava Manufacturing Corporation in Chicago to sell what they called the Lava Lite Lamp. In the late 1970s, US rights were sold to Larry Haggerty, who created a subsidiary of his company, Haggerty Enterprises, called Lava World International, which produced American lava lamps for over 30 years.

In 2003, American lava lamp maker Lava World International (formerly Lava-Simplex-Scribe Internationale) moved its production to China. In 2008, it was acquired by Talon Merchant Capital and its name was changed to Lava Lite LLC. As of 2016, lava lamps were being sold under Lifespan brands in North America. In 2018, the 'Lava Lamp' brand was acquired by toy and gift maker Schylling Inc. of North Andover, MA. who continue to hold the US trademark rights to both the shape and name of LAVA lamp.

When the American rights were sold, Craven Walker retained the rights for the rest of the world, and took on two business partners in the late 1980s, Cressida Granger and David Mulley. They eventually took over the company and changed its name to Mathmos in 1992. Edward Craven Walker remained a consultant to them until his death in 2000. Mathmos continues to make Lava Lamps and related products. They have won two Queens Awards for Export, and the Best Multi-Media prize at the Design Week awards. Astro lava lamp was launched in 1963 and celebrated its 50th anniversary in 2013. Mathmos lava lamps are still made in the original factory in Poole, Dorset.

Lava lamps were very popular back in the groovy 1960s! Many people still have them at home today.

Most lamps light up a room. But lava lamps are mainly just fun to look at. They have coloured wax globules floating around in a transparent liquid.

Lava lamps are also a “groovy” way of seeing physics and chemistry principles in action.

To understand how lava lamps work, you have to understand Kinetic Molecular Theory. It states that all matter is made up of molecules that are always moving. These molecules have kinetic energy. The amount of energy depends on the temperature. When it’s hotter, molecules have more energy. And when they have more energy, they move faster. There are three most common states of matter.

The molecules in solids have the least energy. That means they move more slowly than molecules in liquids and gases.

The molecules in gases have the most energy of all. They move the fastest.

Kinetic molecular theory can help you understand density. Density refers to how much matter there is in a given volume of space.

Have you ever thrown a coin into a fountain or a rock into a pond? You probably noticed that these objects sink in water. And you’ve probably noticed that other objects, like twigs, float on water. The objects that are denser than water sink. And the objects that are less dense than water float.

But what does this have to do with lava lamps? Remember the globules - let’s call them “globs” for short - that float around? At room temperature, the globs are a bit denser than the surrounding liquid. That’s why they sit at the bottom of the lamp. But when you turn the lamp on, the globs heat up. The molecules move faster. The globs become less dense than the surrounding liquid. They rise and start to float around!

So why don’t the globs of wax in a lava lamp mix with the surrounding liquid?

Think about chocolate syrup and milk. They’re miscible liquids. That means they can mix to form a homogeneous mixture.  The chocolate syrup mixes completely with the milk to form yummy chocolate milk!

But some liquids are immiscible. They don’t mix with each other. It all depends on the force of attraction between the molecules in the two liquids.

For example, what happens when you try to mix oil and vinegar - like in a salad dressing? The molecules in the vinegar are more attracted to each other than to the molecules in oil. The molecules in oil are more attracted to each other than to the molecules in the vinegar. No matter how much you shake or stir your dressing, they will never stay mixed together.

But chocolate syrup molecules are attracted to milk molecules. And milk molecules are attracted to chocolate syrup molecules. That’s why you get chocolate milk and not a lava lamp in a glass!

Each immiscible liquid is called a phase. A mixture with two immiscible liquids is called a biphasic mixture. A mixture with more than two immiscible liquids is called a multiphasic mixture.

When you watch the globs float around in a lava lamp, you’re looking at a biphasic mixture!

One of the most interesting features of a lava lamp is the way that the globs float around. But why does this happen? You know that the globs are less dense than the surrounding liquid. And you know that the globs and the liquid are immiscible. So why don’t the globs just rise to the top of the lamp and stay there?

Well, lava lamps are designed so that the temperature at the top is a bit cooler than at the bottom. And what happens to molecules when they cool down? That’s right! They lose energy and move closer together. So when a glob reaches the top of the lava lamp, it contracts. It becomes denser than the surrounding liquid and begins to sink. When it reaches the bottom, the whole cycle repeats!

A lava lamp is an example of a convection current. Convection currents cause liquids and gases to rise and fall because of changes in their density. There are convection currents all around you, even in the Earth’s crust!

You can build your own lava lamp in your classroom or at home! Here’s what you’ll need:

How to make a lava lamp:

Description A lava lamp is a decorative lamp, invented in 1963 by British entrepreneur Edward Craven Walker, the founder of the lighting company Mathmos. It consists of a bolus of a special coloured wax mixture inside a glass vessel, the remainder of which contains clear or translucent liquid. Wikipedia

The whirling globs we remember are made mainly of paraffin wax, with compounds like carbon tetrachloride added to increase its density. The liquid the wax floats in can be water or mineral oil, with dyes and sparkles added for whimsy.