AS/NZS 1301.204rp:1993

This Standard is new to the 1301 series. However an Appita Standard on this subject was published in 1956, but was withdrawn because of its unreliability. This Standard is published with the status of a Recommended Practice rather than a standard because, although it is the best procedure known at this time, it is not particularly accurate. Care needs to be taken in the interpretation of results. The procedure described involves using a standard chart to estimate the size of dirt spots and to either count the numbers of spots with certain size classes , or to calculate the total area of the spots. The determination may be made in either reflected light or transmitted light.