Utilization of STV in estimating the efficiency of penetrant removal operations from examined surfaces
creates a number of additional problems, for in this case not only should one determine the effect of parameters of operations on the flaw detectability (which could be done easily on the base of criteria and methods applied to other operations), but also estimate the intensity of the luminescent background due to the
remaining penetrant dye on the surface. This paper suggests a method and criteria that help in solving these
problems.