Lava lamp
A lava lamp (or Astro lamp) is a decorative novelty item, invented by British accountant Edward Craven-Walker in 1963. The lamp contains blobs of colored wax inside a glass vessel filled with clear liquid; the wax rises and falls as its density changes due to heating from an incandescent light bulb underneath the vessel. The appearance of the wax is suggestive of pāhoehoe lava, hence the name. The lamps are designed in a variety of styles and colours.
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Operation [edit]
A classic lamp contains a standard incandescent bulb or halogen lamp which heats a tall (often tapered) glass bottle. A formula from 1968 US patent consisted of water and a transparent, translucent or opaque mix of mineral oil, paraffin wax and carbon tetrachloride.[1] The clear water and/or mineral oil can optionally be coloured with transparent dyes.
Common wax has a density much lower than that of water, and would float on top under any temperature. However, carbon tetrachloride is heavier 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 the wax expands more than water when both are heated.[2] It also becomes fluid, and blobs of wax ascend to the top of the device where they cool (which increases their density relative to that of the water) and then they descend.[3] A metallic wire coil in the base of the bottle acts as a surface tension breaker to recombine the cooled blobs of wax after they descend.
However, lava lamps made for the US market since 1970 do not use carbon tetrachloride, because its use was banned that year due to toxicity.[4] The manufacturer (Haggerty) states that their current formulation is a trade secret.[5]
The underlying fluid mechanics phenomenon is a form of Rayleigh–Taylor instability.
The bulb is normally 25 to 40 watts. Generally it will take 45-60 minutes for the wax to warm up enough to freely form rising blobs, when operating the lamp at standard room temperature. It may take as long as 2 to 3 hours if the room is below standard room temperature.
Once the wax is molten, the lamp should not be shaken or knocked over 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 means to recombine all of wax is to turn off the lamp and wait a few hours. The wax will settle back down at the bottom, forming one blob once again. Severe cases can require many heat-cool cycles to clear.
History [edit]
A British accountant Edward Craven-Walker invented the lava lamp in 1963, after watching a homemade egg timer made out of a cocktail shaker filled with liquids bubbling on a stove top at a pub.[6] His U.S. Patent 3,387,396 for "Display Device" was filed in 1965 and issued in 1968.[7] Craven-Walker's company was named Crestworth and was based in Poole, Dorset, in the United Kingdom. Craven-Walker named the lamp "Astro", and had variations such as the "Astro Mini" and the "Astro Coach" lantern.
Craven-Walker presented it at a Brussels trade show in 1965, where the entrepreneur Adolph Wertheimer noticed it. Wertheimer and his business partner William M. Rubinstein bought the US rights to manufacture and sell it as the "Lava Lite" via Lava Corporation or Lava Manufacturing Corporation. Wertheimer sold his shares to Hy Spector who took the product into production, manufacturing and marketing the Lava Lite in his Chicago factory at 1650 W. Irving Park Rd in the mid-1960s. Rubinstein stayed on as a vice president.
The lamps were a success throughout the 1960s and early 1970s. Lava Corporation's name changed to Lava-Simplex-Scribe International in the early 1970s, and they also made instant-loading camera-film cartridges, as well as postage-stamp vending machines. In the late 1970s Spector sold Lava Simplex International to Michael Eddie and Lawrence Haggerty of Haggerty Enterprises. Haggerty Enterprises continues to sell their lava lamp in the US. "Lava lamp" has been used as a generic term but Lavaworld has claimed violation of trademarks.[8]
In the 1990s, Craven-Walker, who had retained the rights for the rest of the world, took on a business partner called Cressida Granger. They changed the company name to Mathmos in 1992. Mathmos continues to make Lava Lamps and related products. Mathmos lava lamps are still made in the original factory in Poole, Dorset, UK.
Hazards [edit]
In 2004, a Kent, Washington man was killed while attempting to heat up a lava lamp on a kitchen stove while closely observing it from only a few feet away. The heat from the stove built up pressure in the lamp until it exploded and a shard pierced his heart causing fatal injuries.[9]
The circumstances of his death were later reenacted in a 2006 episode of the popular science television series MythBusters. The show found that even if shards of glass are not thrown with lethal velocity during such an attempt, the resulting spray of hot liquid from the lamp could easily cause severe burns to anyone nearby. The show also noted that the safety instructions clearly state that lava lamps should not be heated by any source other than the specifically rated bulbs and purpose-designed bases that are provided.[10]
Homebrew lava lamp recipes can be found over internet, however some of them rely on combinations of highly flammable components like alcohol. Such lamps could represent a serious fire hazard in the case of rupture when heated over a light bulb. A safe wax formulation that uses distilled water as its transport fluid is also available for hobbyists.[11]
See also [edit]
- Lavarand, a random number generator that used lava lamps.
- Plasma globe
- Lava
Notes [edit]
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This article uses bare URLs for citations. (May 2013) |
- ^ U.S. Patent 3,570,156 p 2 line 30
- ^ U.S. Patent 3,570,156 p 1 lines 40 and 45
- ^ U.S. Patent 3,570,156 p 1 line 47
- ^ [1]
- ^ [2]
- ^ Abigail Tucker (March 2013). "The History of the Lava Lamp: At 50, the legendary relic of the college dorm room is still groovy after all these years". Smithsonian magazine. Retrieved Feb 28, 2013.
- ^ Patent 3570156
- ^ Legal Threats from Lavaworld. - Oozing Goo Lava Line
- ^ Lava Lamp Death at Snopes.com; AP story (via Fox News)
- ^ Mythbusters, Season 4, Episode 60: Earthquake Machine, first aired August 30, 2006.
- ^ Standard Goo Kit at Oozinggoo.com;
External links [edit]
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Wikimedia Commons has media related to: Lava lamps |
- Official site (UK)
- How Do Lava Lamps Work? (from The Straight Dope)
- How Liquid Motion Lamps Work (from howstuffworks.com)
- Basics of lava-lamp convection, by Balázs Gyüre and Imre M. Jánosi, Phys. Rev. E, 80, 046307 (2009).
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