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Physical Chemistry

What’s that Stuff

What's that stuff? Lava Lamps

A density lesson inspired the Woodstock generation

by Carmen Drahl
February 18, 2008 | A version of this story appeared in Volume 86, Issue 7

Credit: iStock
Credit: iStock

NOSTALGIA PROBABLY ranks somewhere near the bottom on the list of causes of kidney failure. But a 1996 report in the Annals of Emergency Medicine relays the story of a 65-year-old man who guzzled the contents of a certain iconic 1960s light fixture and then spent three months in a hospital to recover from his indiscretion. The journal didn't name the manufacturer of that particular lamp. But most people would call it a Lava lamp, the trademark name for one company's product that's widely used to describe liquid motion lamps and their characteristic undulating flow.

Liquid motion lamps were invented in the U.K. The story goes that Edward Craven Walker, leader of a World War II Royal Air Force squadron and a nudist filmmaker, drew inspiration for the groovy lamp from a pub's egg timer. The patent literature suggests that there is some truth to that tale. Walker was certainly the first to commercialize the lamps, which went on to embody the "Age of Aquarius."

Those early patents aren't easy-to-follow recipes, but they do discuss how the kitschy lamps work. The shapely vessel houses two main ingredients that are mutually insoluble. The key to the lamp's ever-changing serpentine flow is to closely match the density of the two layers. A heat source tweaks the density of one component so that when warm, it is less dense than the other component and so floats to the top. Upon cooling, it is denser than the other component and sinks to the bottom.

The random motion captivates people's interest, and is something that other collectibles very rarely recreate, notes Anthony Vassallo, a liquid motion lamp collector who helps maintain the tribute websites and "You never know how the lava is going to flow."

Water and wax, which the original patents name as main ingredients, remain components of the commercial recipe, says Tom Spain, vice president of sales, marketing, and product development for Haggerty Enterprises, the official U.S. manufacturer of Lava brand lamps. Additional agents, he explains, help the wax gently plume upward instead of breaking apart into bubbles as it is heated and keep wax from sticking to the sides of the container.

Walker's U.S. patent mentions additives such as dye, mineral oil, carbon tetrachloride, and polyethylene glycol (PEG), but the exact formula of commercial lamps is a trade secret. Spain tells C&EN that only five or six staff chemists know the formula and are in charge of occasional reformulations. Densities must be recorded for each batch of wax that Haggerty makes, which is mixed in 5-foot-tall vats in factories in China.

Last but not least, the water layer is added to the cooled wax very slowly so as to avoid creating emulsions, which are cloudy-looking oil-water mixtures. In fact, the recipe for the water layer is carefully adjusted to perfectly complement the density of each unique batch of wax.

As far as motion lamp recipes go, a study of the aforementioned emergency room patient provides more detailed information than do patents and corporations. Gas chromatography-mass spectrometry analysis of the patient's blood and the remaining lamp liquid revealed components mostly consistent with Walker's patent. But here's food for thought for those with an insatiable thirst for liquid motion lamps: The study concluded that PEG was probably to blame for the kidney toxicity.

PATENTED FORMULAS aside, a potpourri of do-it-yourself recipes is available on websites like Many of these recipes call for both flammable alcohols and a heat source, a dangerous combination without the right expertise and supervision.

Sprinkled throughout the home-brew websites are also allusions to a liquid motion lamp at the Smithsonian in Washington, D.C. The lamp's place of honor is a darkened nook in the Smithsonian National Museum of Natural History. Massive rocks dredged from the remnants of ancient volcanic eruptions flank the lamp. Sorena S. Sorensen, the museum's chair and curator-in-charge of rock and ore collections, helped dream up the display 10 years ago. The goal, she says, was to give museum patrons a crash course in the science of molten rock, which rises through the earth's crust to become the underpinnings of volcanoes.

At first, Sorensen says, the display case interfered with the lamp's performance, because the lack of airflow kept the wax globules from cooling down and sinking.

Lamp ventilation is an issue during factory quality-control testing as well, Spain notes, and it requires a room with a specialized cooling system. At the Smithsonian, curators drilled strategically placed holes in the display case to fix their lamp. That persistence paid off, Sorensen says, giving the museum "something dynamic, something that would be a magnet for kids."

Mission accomplished. When C&EN visited the museum, five-year-old Joshua from Arizona galloped toward the tower of glowing ooze and pressed up against the glass case, mesmerized. "I want one of these at home," he told C&EN.



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