Barium and strontium oxides give a dim flame luminescence. No specific preparation is required. Any suitable-size piece of limestone will be adequate for this demonstration. MFH uses a lump of limestone because it is more robust. This is the usual industrial preparation of calcium oxide e.g. in the production of cement.
Old limekilns are to be found in many parts of the country, some of considerable antiquity.
The small area of lime is heated to some 2000K by the flame but, in addition to the incandescent light produced, additional blue light is emitted due to thermoluminescence. The combined emission appears as an intense white light. After many attempts to improve the efficiency of gas lighting a giant step was made in 1887 when the Austrian physicist Carl Auer von Welsbach made the first successful gas mantle. Welsbach used a fabric tube that had been soaked in a solution of soluble salts of thorium and cerium and then dried. The fabric was arranged around the burner, and when first lit it burned away leaving a delicate open structure of thorium and cerium oxides.