The blanks used had a diameter of 275 mm and thickness of 340 mm with artificial defects (holes drilled radially) of diameters 9.3, 8.7, 4.6, 4.4, 2.9 and 2.8 mm and depth of about 20 mm. It is well known that in industrial radiography with conventional sources, unsharpness plays a key role in defect delectability. At thicknesses greater than 50 mm steel equivalent, this unsharpness is a combined measure of the geometry, film and screen combination. Delectability of defects, especially in thick walled materials, is a function of the unsharpness and also the location of the defect within the object. Hence, before the actual radiography was taken up, empirical calculations were made using a specifically developed computer program to determine the variation in unsharpness with thickness. From the experimentally observed contrast, the achievable sensitivity was calculated. Theoretical estimates revealed that defect sensitivity of the order of 2.4% could be easily achieved with the X-ray beam oriented along the diameter of the insulator blank. Since steel is the most commonly used material for radiography, the radiographic equivalence factors were determined to be about 0.31. This was done by comparing the film densities obtained under three different thicknesses of the insulator blank with the image of a standard steel step wedge both taken with identical radiographic parameters. Using this radiographic equivalence factor, the radiographic parameters were standardised. Experiments were conducted with the defects in a variety of orientations. It was observed that the 8.7 mm hole could be detected in the insulator with a thickness of 340 mm resulting in a sensitivity of 2.5%. This is very close to the theoretically estimated sensitivity of 2.4%, thus validating the empirical approach.