Production of White Light

Pyrotechnic light production has two purposes illumination and recognition. In other words, it either is important to light up an object or an area to make it visible to the eye or to a camera, or one desires to see or scan by instrument the light source itself as a signal and, in the case of fireworks, as an esthetic design of light. 

The light of a full moon on a clear night has been given as yielding an illuminance of the ground of 0.025 foot candles (Im/ft ), which may be called the minimum of useful light for a military operation while 0.05—0.1 foot candles are required for some night operations.  

I million candlepower will satisfy this requirement from an altitude of 4000 ft and for a 5000-ft operational radius. The same candle would have to drop to 2000 ft for 0.05—0.1 foot candles at an optimum radius of 4000 and 2500 ft, respectively. More details on formulas and charts for illumination can be found in a Picatinny report.  

The gist of this thumbnail sketch is that a candlepower of I 2 million over the longest possible or practical burning time of 2-3 minutes is needed for many operations. Air-dropped parachute flares of this size exist as described below, as do smaller less powerful units (but designed for operation at lower altitude) in the form of ground-launched howitzer or mortar-fired illuminating shells. 

Surveys of existing munitions (for illumination) are found in technical manuals, 43,258 but without pyrotechnic details such as formulas, The quoted candlepower figures may be much too low compared with those now obtained from the same munitions due to improvements since these manuals were compiled. Dr. Hart quotes the doubling and tripling of light outputs between 1948 and 1958 on numer- 

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For the production of white light, a temperature of >1500°C is required. The incandescent carbon volatilizes above 3600°C and hence reasonable brightness can be obtained from the arc produced from carbon electrodes. 

The presence of incandescent solid or liquid particles in the flame will adversely affect color quality. The resulting "black body" emission of white light will enhance overall emission intensity, but the color quality will be lessened. A "washed out" color will be perceived by viewers. The use of magnesium or aluminum metal in color compositions will yield high flame temperatures and high overall intensity, but broad emission from incandescent magnesium oxide or aluminum oxide products may lower color purity. 

In the following chapters, pyrotechnic light production will for purely practical reasons rather than as a logical arrangement be divided into the creation of white light other than flashes, for military uses with... 

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