Astro lava lamp.]]

A lava lamp (or Astro lamp) is a novelty item used more for decoration rather than illumination — the slow, interesting rise and fall of variously-shaped blobs of wax in it is suggestive of lava; hence, the name. The lamps are available in a variety of styles and colors of wax and liquid.

Operation

The lamp contains a standard incandescent bulb or halogen lamp which heats a tall (often tapered) glass bottle containing water (often with glycerol derived additive) and a transparent, translucent or opaque mix of wax and carbon tetrachloride (although other combinations may be used).^[1] The wax is slightly more dense than water at room temperature but is less dense under warmer conditions.^[2] This occurs because wax expands more than water when both are heated.^[3] When heated, the wax becomes fluid, its relative density decreases, and blobs of wax ascend to the top of the device^[4] where they cool (which increases their density relative to that of the water's) and then descend. 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. The underlying mechanism is a form of Rayleigh–Taylor instability.

The bulb is normally about 25 to 40 watts. It may take 45 to 60 minutes for the wax to warm up enough to freely form rising blobs (depending on the original temperature). It may take 2 to 3 hours if it has been in a cold room for a long time.

Once the wax is molten the lamp should not be shaken or knocked over or the two fluids may emulsify and the wax/blobs will remain cloudy rather than clear. Some recombination will occur as part of the normal cycle of the lava 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.

History

Englishman Edward Craven-Walker invented the lava lamp in 1963. His U.S. Patent 3,387,396 for "Display Device" was filed in 1965 and issued in 1968.^[5] 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 U.S. 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-60s. Rubinstein stayed on as a vice president. The lamps were a success throughout the 1960s and early 70s. Lava Corporation's name changed to Lava-Simplex-Scribe International in the early 1970s, and made instant-loading camera-film cartridges, as well as postage-stamp vending machines.

In the late seventies Spector sold Lava Simplex International to Eddie Sheldon and Larry Haggerty of Haggerty Enterprises. Haggerty Enterprises continues to produce and sell the Lava Lamp in the US, using the name of Lavaworld. "Lava lamp" has been used as a generic term but Lavaworld has claimed violation of trademarks.^[6] Lavaworld has closed production in the USA and has outsourced their lamps to China.^{[citation needed]}

In the 1990s, Craven-Walker, who had the rights to England and Western Europe, sold his rights to Cressida Granger, whose company, Mathmos, continues to make Lava Lamps and related products. Mathmos lamps are still made in the original factory in Poole. Mathmos is the only company worldwide to produce the lamp using the original formula, and the sole original manufacturers of the lava lamp.^{[citation needed]}

Hazards

In 2004, Phillip Quinn, a 24-year-old of Kent, Washington, was killed during an attempt to heat up a lava lamp on his 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, spraying shards of glass with enough force to pierce his chest, with one shard piercing his heart and causing fatal injuries.^[7] The circumstances of his death were later repeated and confirmed in a 2006 episode of the popular science television series MythBusters. The show also proved 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 specially-designed bulbs and bases that are provided.^[8] According to the TV show 1000 Ways to Die, a man suffered a similar fate in 1992.

See also

• Lavarand, random number generator that used lava lamps.
• Plasma globe
• Lava

Notes

External links

• 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).