Bi- magnetic powder has the remarkable properties of appearing black when dusted on a light coloured surface and appearing silver when dusted on a dark coloured surface. The greatest advantage of using Bi- magnetic powder is that the lifted prints will be black when placed on a white backing card. This eliminates the bother of comparing latent prints with light coloured ridges on a black background against rolled prints with black ridges on a white background. It also means that only white latent print lift backing cards will be needed. There is no need for black latent print lift backing cards with Bi powder.
Also known as 2 tonne, duel or bio chromatic