To grade tiles in control lines of tile factories, some methods are required for detection of all different types of defects which may exist on tiles during production. According to experts, one of the defects which reduce quality of tiles are cracks and spots. These kinds of defects are called sharp defects which generate low width and high contrast structures in image. One of the image processing tools with which these low width and high contrast structures can be detected in an image is the use of morphological operators such as dilation and erosion. In this paper, Fuzzy morphological operators are used to detect defects. Efficiency of detection depends on the used mask a lot. To overcome this challenge, genetic algorithm has been used for optimization of mask. Desirable results were obtained for detection of sharp defects and gradation of all types of simple, colorful and designed tiles by simulating this method in MATLAB medium and performing abundant tests on images of all types of tiles and this case i.e. gradation of all types of tiles is one of the advantages of this method over the previous methods.