|
A lava lamp (or Astro lamp) is a decorative novelty item, invented by British accountant Edward Craven Walker, the founder of Mathmos, in 1963. The lamp contains blobs of coloured wax inside a glass vessel filled with clear or translucent 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. ==Operation== A classic lava lamp contains a standard incandescent bulb or halogen lamp which heats a tall (often tapered) glass bottle. A formula from 1968 U.S. patent consisted of water and a transparent, translucent or opaque mix of mineral oil, paraffin wax and carbon tetrachloride.〔 DISPLAY DEVICE, Edward C. Walker, Nov. 13, 1968〕p. 2, line 30 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.〔p. 1, lines 40 & 45 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.〔p. 1, line 47 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 in China for the U.S. market since 1970 do not use carbon tetrachloride, because its use was banned that year due to toxicity.〔(【引用サイトリンク】title=Toxicological Review of Carbon Tetrachloride ) EPA/635/R-08/005F〕 The manufacturer (Haggerty) states that their current formulation is a trade secret.〔(【引用サイトリンク】publisher=Chemical & Engineering News )〕 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 form freely 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. In 2015 a new design that uses ferrofluid in place of wax was introduced into the market. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「lava lamp」の詳細全文を読む スポンサード リンク
|