“…Burdevold's window technic (1948), which involved covering the crown with wax except for a standardsized area, has been used by several workers (e.g. Stralfors, 1958, andJenkins et al, 1952). The method is time consuming, and a large number of tests must usually be carried out because of considerable variation in the solubility of areas from the same tooth as well as that of areas from different teeth.…”