Characterising crystals and anti-reflective coatings

The watch crystal is, along with the dial, an essential part of the watch's image. Its brittleness, scratch resistance and transparency are important characteristics which are carefully inspected:

• Crystal type inspection: sapphire, glass…
• Crystal hardness measurement: Vickers, Knoop, Berkovitch instrumented nanoindentation
• Crystal impact strength; ball drop test as per ISO 14368-3 (NIHS 61-13
• Crystal static load strength as per ISO 14368-3 (NIHS 61-13)
• Crystal scratch and resistance as per ISO 23160
• Characterising anti-reflective coatings: optical characteristics, color, wear and scratch resistance, adhesion…