A 19th century unit of luminous intensity mainly used in France (literally, star candle). Sometimes referred to in English as a “French star candle.”
One bougie de l’étoile is the luminous intensity of a standardized candle made of stearin burning at the rate of 10 grams per hour with a flame height of 52.4 millimeters. There were two types of star candle, identified as being packed 6 to a package or 5 to a package. The respective dimensions are given in source 1, below.
One bougie de l’étoile is about 0.136 carcel.
The French Star candle burns 10 grams of material per hour. Peclet, in 1830, compared the first candles made by de Milly; he found that they gave a light whose intensity was equal to 1/7 carcel. Candles of this quality are no longer to be found; the best candles made in France do not equal more than 1/8 carcel.
According to Monnier, the employment of the Star candle as a photometric unit requires not only a consumption of 10 grams per hour, but a height of flame of 52.4 mm. These candles come 5 or 6 to the package.
The candles with 5 in a package weigh 100 grams each; their dimensions are: total length, 306 mm.; length of cylindrical part, 290 mm.; diameter above, 20 mm.; diameter below, 22 mm.; the wick is composed of 81 threads.
The candles with 6 in a package weigh 83.3 grams; their dimensions are: total length, 274 mm.; length of cylindrical part, 258 mm.; diameter above, 20 mm.; diameter below, 21.5 mm.; the wick has 81 threads.
The comparisons of Star candles with other candles not being numerous on account of their comparatively small employment, we shall give immediately the most probable values of this standard of light as a function of the normal carcel lamp.
Monnier found the following mean values. A Star candle equals 0.136 carcel with a mean consumption of 10 grams per hour, and 0.136 carcel also with a height of flame of 52.2 mm. For candles with 6 in a package, the corresponding values are 0.131 and 0.132 carcel.
In the same way 1 normal carcel equals 7.4 candles of 5 to the package, or 7.6 candles, 6 to the package, taking as the normal candle that which consumes 10 grams of stearine per hour, or that which gives a flame 52.5 mm. in height.
A Treatise on Industrial Photometry with Special Attention to Electric Lighting.
Authorized translation from the French by George W. Patterson, Jr., and Merib Rowley Patterson.
New York: Van Nostrand Co, 1894.
Pages 121. The first French edition, Traité de Photométrie Industrielle Spécialement Appliquée à L’éclairage électrique, was published in 1892.
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Last revised: 22 February 2011.