Overall Surface Texture Change

The cracked sealant surfaces of samples PU1, PU2, and MS2 show the highest ratings for overall surface texture change. The values for the silicone sealants, SRI and SR2, indicate that their surfaces do have some variations. Visual observation of these two specimens indicates heavy accumulation of dirt particles.

FIG. 8—Visual color change of samples calculated on the basis of change in average gray levels.

FIG. 9—Enhanced and processed images of weathered sealant surfaces. Cracking/Crazing

PU1, PU2, and MS2 have apparent cracks and their severity is measured based on crack density and crack width. It is notable that all three specimens show comparable crack density values. The crack width measurement indicates that PU2 displays the most severe cracks in terms of crack width. The PS2 speci­men shows some crazing; however, automatic detection of the crazing on this sample was not feasible.