Shown in this video is a 3” silver coated substrate attached to an abrasion test apparatus. The demonstration was conducted over a three day period of time at Photonics West 2019.

During the show, almost 4,000 rotations were made depicting the durability of Guernsey’s silver (M14) using MIL specifications for moderate abrasion (applying 1 to 1-1/2 pounds of pressure through cheesecloth pad 3/8” in diameter).
The MIL test specifies 50 passes. The surface of the optic was not cleaned allowing ambient dust to settle on the part and dragging added contaminants across the surface. The coating was torture tested and does not end up pristine at the end of three days, however, the damage is extremely minor.