The residue on the lower disc, if examined before carbonisation, is fawn-coloured with non-characteristic spots.
characteristic char·ac·ter·is·tic (kār'ək-tə-rĭs'tĭk)
The part of a logarithm to the base 10 that is to the left of the decimal point. For example, if 2.749 is a logarithm, 2 is the characteristic. Compare mantissa.