Single-Number Tolerances For Coloured Glass Specifications

Chromaticity data of glasses were measured by the Hunter Colour-Colour Difference Meter and the results converted to single numbers representing distances in colour space between each glass and a glass in the centre of an appropriate specification. This simple evaluation gave a good correlation to visual specifications as the more complicated evaluation of spectrophotometric data. A probable error or 5% existed for each method if the alternate method was regarded as correct.