classic lamp contains a standard incandescent bulb or halogen lamp which heats a tall (often tapered) glass bottle containing water and a transparent, translucent or opaque mix of mineral oil, paraffin wax and carbon tetrachloride.[1] The water and/or mineral oil can be coloured with dyes. The density of common wax is much lower than that of water and would float on top under any temperature. However, the 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 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 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.
The underlying mechanism is a form of Rayleigh–Taylor instability.
The bulb is normally 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 depending on the temperature.
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 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.
1.14, 29.12.12.
apparel someone has pilfered my earlier version of this and i can't find it
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