b'TECHNICAL & RESEARCH Continued from page 39diameter circle (Figure 3). A black and white5. Post-Impact Weights and Granule Counts. image was created from the original color image,Weights of the samples and granule counts at a process called color thresholding. This enabledeach impacted zone were obtained a second time the computer program to determine quantitativefor each sample following impact. In addition to information regarding the image (granule countsweighing the full samples using a precise scale, and exposed bitumen area). In addition to imagegranules equal in number to those lost during analysis, manual counts of the granules were alsoimpact were also weighed. Comparisons were conducted.made between pre- and post-impact images (Figures 5 and 6). Figure 2. Weighing of sample. Figure 3. Granule identification through image analysis.4. Impact Testing. A 5-pound steel missileFigure 5. Sample 5-MB-G-1Figure 6. Sample 5-MB-G-1 released from a height of 53-inches impactedpre-impact. Orange arrowspost-impact. Orange arrows indicate some differencesindicate some differences each quadrant of the sample per ASTM D3746.between the pre-impact andbetween the pre-impact and The steel missile was held at the top of the droppost-impact images.post-impact images.tube with a pin until the sample was ready to be6. Desaturation. Desaturation is the process impacted. A laser guide was used to align theof removing the bitumen from the membrane missile with the center of the impact zone. Seesamples using a solvent to expose the Figure 4. reinforcement. One quadrant of each sample was desaturated to allow the membrane reinforcement to be visually inspected for damage due to the impact (Figures 7 and 8). Figure 4. Testing apparatus at left; steel missile within drop tube at upper right; and laser spot alignment for missile drop within aFigure 8. Polyester typical 3-inch diameter circle at lower right.Figure 7. Fiberglassand fiberglass dual reinforcement from areinforcement from a modified bitumen base ply. modified bitumen cap ply.40 www.mrca.orgMidwest Roofer'