When a moistened clump of borax powder (being hydrated sodium borate) is held on the tip of an inert wire in a flame it will fuse into a clear glassy bead, called a borax bead. If the borax bead is subsequently powdered with a substance containing an unknown element and then held within the flame again, depending upon whether it is held in an oxidising or reducing part of the flame, the bead may become coloured as the substance decomposes and the oxide of the element dissolves in the bead. This coloration is used as a test for various elements. For some elements, the test is ambiguous, in that some elements can impart the same coloration to the bead. But if the test is repeated in both the oxidising and the reducing parts of the flames, further discrimination can be achieved in those instances when a different colour is produced. If the borax bead tests are combined with the flame coloration test, the element can usually be identified provided it is one that imparts colours.
Sometimes the borax bead changes colour as it cools, and this observation can further aid determination of the element. For some elements the borax bead takes on a different appearance or colour depending upon the concentration of the test substance, whether it undersaturates, saturates or supersaturates the glassy bead. The colours quoted here are those imparted by the higher concentrations of test substances. The first colour shown is that for the oxidising part of the flame, the second for the reducing part.
Please note that, at best, the on-screen colours of the bead are very poor representations of the actual colours, but the best that can be achieved on screen.
