Many of the above are unfit for indoor exhibitions owing to the amount of sulphurous gas given off. For tableaux in churches, schools and private houses, the best light is undoubtedly magnesium or, where it can be had, the lime light (sometimes, though erroneously, called the calcium light). Both of these lights are very powerful, and any color may be obtained by the use of pieces of differently colored glass. A very effective arrangement consists of a tin box, which may be made out of one of those cases in which crackers are imported. Pro cure good-sized pieces of red and blue glass, the red being a soft, warm tint, such as will add a richness to the complexions of those upon whom the light is thrown. Arrange one end of the tin box so that these glasses may be slipped over a large hole in it. The opposite end of the box should be highly polished so as to act as a reflector, and a hole should be cut in one side so as to allow of the introduction of the magnesium.
In every case the burning matter should be so shaded that it may not be seen by the audience. If the direct light from the burning body meets the eyes of the spectators the reflected light from the objects composing the tableau will have no effect.
Where arrangements for lime or magnesium lights cannot be made, the following may be used.
Chlorate of potash, 12; nitre, 5; finely powdered loaf sugar, 4; lycopodium 2.
Nitrate of baryta, shellac and chlorate of potassa, all finely powdered, equal parts by bulk.
Nitrate of strontia, shellac and chlorate of potassa, all finely powdered, equal parts by bulk.
The brilliancy of these fires will depend largely upon the thoroughness with which the materials are finely powdered and mixed. [See caution at end of this article.]
Braunschweizer recommends the following formidse as giving excellent results, the lights being good without producing injurious frimes:
Nitrate of strontia, 9; shellac, 3; chlorate of potassa, l 1/2.
Nitrate of baryta, 9; shellac, 3; chlorate of potassa, l 1/2.
Ammoniacal sulphate of copper, 8; chlorate of potassa, 6; shellac, 1.
The Pharmacist gives the following formula for "Red Fire," which will not evolve sulphurous acid during combustion: nitrate of strontia, 1 lb.; chlorate of potassa, 1/4 lb.; shellac, 1/4 lb.
These ingredients must be thoroughly dried, powdered separately, and carefully mixed by gentle stirring.