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A lantern is a portable lighting device used to illuminate broad areas. Lanterns may be used for signaling, or as general light sources for camping. Dim varieties are often used for decoration.

The term "lantern" is also used more generically to mean a 'light source' or the enclosure for a light source, i.e., the housing for the lamp and lens -- that is the top section -- of a lighthouse.

Traditional and decorative lanterns

Stone lantern in a Chinese Garden
The simplest technology used is the candle lantern which can be lit with fire. Candles give only a weak light, and must be protected from wind to prevent flickering or complete extinguishment. Thus the lantern was invented. A typical candle lantern is a metal box or cylinder with glass side panels and an opening or ventilated cover on the top.
Decorative lanterns exist in a wide range of designs. Some hang from buildings, while others are placed on or just above the ground. Paper lanterns occur in societies around the world. Modern varieties often place an electric light in a decorative glass case.

The ancient Chinesemarker sometimes captured fireflies in transparent or semi-transparent containers and used them as (short-term) lanterns. Raise the Red Lantern, a Chinese film, prominently features lanterns as a motif.

Use of fireflies in transparent containers was also a widespread practice in ancient India. But since these were short term solutions, the use of fire torches was more prevalent.

Modern fueled lanterns

A railroad brakeman's signal lantern
All fueled lanterns are somewhat hazardous due to the danger of handling flammable and toxic fuel, danger of fire or burns from the high temperatures involved, and potential dangers from carbon monoxide poisoning if used in an enclosed environment.

Simple wick lanterns remain available. They are cheap and durable, but provide little light and are unsuitable for reading. They require periodic trimming of the wick and regular cleaning of soot from the inside of the glass chimney.

Mantle lanterns use a woven ceramic impregnated gas mantle to accept and re-radiate heat as visible light from a flame. The mantle does not burn (but the cloth matrix carrying the ceramic must be "burned out" with a match prior to its first use). When heated by the operating flame the mantle glows incandescently. Such lanterns are very bright, and can easily be used as reading lights. The heat may be provided by a gas, by kerosene, or by a pressurized liquid such as "white gas," which is essentially naphtha. For protection from the high temperatures produced and to stabilize the airflow, a cylindrical glass shield called the globe or chimney is placed around the mantle.

Manually pressurized lanterns using white gas (also marketed as "Coleman Fuel" or "Camp Fuel") are manufactured by the Coleman Company in one and two mantle models. Some models are "dual fuel," which can also use gasoline. These are being supplanted by a battery-powered fluorescent lamp models by many manufacturers including Coleman. Liquid fuel lanterns remain popular where the fuel (see portable stove for a discussion on fuel) is easily obtained and is in common use.

Many portable mantle-type fuel lanterns now use fuel gases that becomes liquid when compressed, such as propane, either alone or combined with butane. Such lamps usually use a small disposable steel container to provide the fuel. The ability to refuel without liquid fuel handling increases safety and additional fuel supplies for such lamps have an indefinite shelf life if the containers are protected from moisture (which can cause corrosion of the container) and excess heat.

The leading manufacture of kerosene mantle lamps in the United States is the Aladdin Mantle Lamp Company, which has long produced an extensive line of utilitarian and decorative mantle lamps. A specialized cylindrical wick with a central airflow tube satisfies the high and uniform heating demands of the mantle.

Modern electric lanterns

Some lanterns are battery-powered and have a simple lightbulb, but power supply to operate a Fluorescent lamp. They are easy to use and comparatively durable, but less bright than propane or liquid fuel lanterns, require battery replacement, or if rechargeable and not constantly plugged in must be brought to full charge every few months.

Some rechargeable fluorescent lanterns may be plugged in at all times and may be set up to illuminate upon a power failure, a useful feature in some applications. During extensive power failures (or for remote use), supplemental recharging may be provided from an automobile's twelve volt electrical system or from a modest solar powered charger. Solar-powered lanterns have become popular in developing countries where they provide a safer and cheaper alternative to kerosene lamps.

Battery-powered lanterns utilizing LEDs are becoming increasingly popular due to improvements in LED technology and reduced production costs. LEDs have become brighter and more rugged, and typically run longer (due to low current draw from the batteries) than incandescent bulbs or fluorescent tubes of comparable brightness.

References

  1. Terry Pepper, Seeing the Light, Lighthouses of the western Great Lakes, Illumination.
  2. Ashden Awards case study on solar-powered lanterns in India


See also




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