Liquid motion lamps, commonly known as lava lamps, were invented in 1963 by Edward Craven Walker, a British accountant. Unlike most lamps, lava lamps are not acquired for the sole purpose of lighting a room. Most people buy lava lamps because they are fun to look at and are capable of lighting one’s mood. Edward Craven Walker reportedly once said, “If you buy my lamp, you won’t need to buy drugs”.
Besides mood lighting, lava lamps have also been used as random number generators. Some programs were made to change the motion of lava globules into truly random numbers for use in cryptography.
Edward Craven Walker founded the lighting company, Mathmos, which has produced millions of lava lamps over the years. The lava lamps were marketed under the name Astro Lamps. They had peak popularity in the 1990s, with Mathmos selling over 800,000 lamps a year. Lava lamps are still sold every year, and many people have them at home. Some are still in possession of the lava lamps from decades ago.
How are lava lamps made?
The process of making lava lamps begins with the production of custom-made glass bottles. Molten blobs of glass are dropped into a molt. The bottles are shaped into the required shape by a machine blowing air into the top of the bottle. The newly shaped bottles are allowed to cool.
They are then inspected by hand to ensure they are perfectly shaped. Each bottle is also inspected to ensure it can withstand heating and cooling. Quality control is highly important.
With a perfectly shaped glass bottle in place, the next step is metal spinning. A spinning tool is used to spin a thin sheet of steel into the right shape. The base and the cap of the bottle are hand-spun and subsequently polished. The next step is the filling of the lamp.
We know that the lamp is filled with liquid. What we might not know is that a metal spring is also included. The primary function of the metal spring is to distribute the heat. The exact formula of the fluid in a lava lamp is a closely guarded trade secret (although some guys have been said to have done a pretty good job of figuring it out).
Once the two liquids are mixed, the bottle is submerged in hot water. This water bath cleanly separates the liquids and sees that no wax is stuck to the side of the bottle. Lids are glued on and the bottles are ready to go.
How do lava lamps really work?
The fundamental fluid mechanics phenomenon in lava lamps is a form of Rayleigh-Taylor instability.
For a lava lamp to work, density is a major key. There are two major components in a lava lamp: a colored solution and a colored wax globule that sits in it. The whirling globules are made mainly of paraffin wax with an addition of compounds like carbon tetrachloride to increase their density. The liquid the globs of wax floats in can be mineral oil or water with sparkles and dyes added to make it fanciful and more aesthetically pleasing.
Lava lamps are designed in a variety of styles and colors but the components are the same. A classic lava lamp contains an incandescent light bulb or halogen lamp which heats up the glass bottle. The light bulb is usually 25-40 watts.
The density of paraffin wax is lower than that of water, and at any temperature, it would float on top of the water. Carbon tetrachloride is denser than water, and fortunately for the makers of lava lamps, it is non-flammable and miscible with wax.
Carbon tetrachloride is added to the wax to increase its density at room temperature and make it slightly higher than that of the colored water or mineral oil in the glass bottle.
When the lava lamp is turned on, the light bulb in the base starts to heat up the lamp’s interior. Generally, it takes 45 minutes to an hour for the lamp to warm up enough to form freely rising blobs when the lamp is used at standard room temperature and as long as 2 to 3 hours in cooler rooms.
The wax expands when heated. This increase in the volume of the wax decreases its density and causes blobs of wax to float and ascend to the top.
When the blobs of wax hit the top, they cool down and decrease in volume. The density of the blobs increases relative to that of the water or mineral oil in the glass bottle. Consequently, the blobs of wax descend. The metallic spring at the base of the bottle breaks the surface tensions of the cooled blobs, allowing some recombination to occur. And thus, the cycle continues.
The only way to recombine all of the wax is to turn off the lamp and wait for a few hours. The wax returns to the bottom and settles into one blob again.
Once the wax is molten, it is advised not to agitate the lamp. If agitated, the two fluids may emulsify, and the fluid surrounding the wax will remain cloudy rather than clear. It is also advisable not to leave lava lamps on for more than 8 to 10 hours straight.
The exact composition of the wax and liquid are trade secrets, but they are invariably being improved upon. The newest design was the addition of ferrofluid to the wax in lava lamps. The ferrofluids have microscopic magnetic particles suspended in them, which allows us to interact with our lava globs using a magnet.
Making a basic lava lamp at home is quite possible with the use of ingredients like baking soda, vinegar, and other materials that can be easily obtained.
Whether bought or homemade, it is advised not to drink the contents of a lava lamp. We know humans are curious beings and this curiosity sometimes leads to bad things happening. The components of a lava lamp are toxic and many people have been hospitalized for consuming the contents.
