I hinted yesterday at the fact that there are many ways a crystal can be attached to a watch so I thought I would run through them.
1. Many mineral glass crystals are held in place by epoxy. This is especially true when there is a thin metal border on the underside of the crystal like on many Seiko dress watches. 2. Mineral glass and sapphire crystals can also be held in place by a gasket, like in the picture. The gaskets compact as the crystal is forced inside of them and it expands out creating a seal between the crystal and the bezel of the watch. 3. On a Rolex the gasket actually locks into a groove on the crystal and the bezel forces the gasket in against the crystal and the case of the watch holding all three pieces together. 4. Many acrylic crystals (like the one pictured) behave like a gasket themselves. Their shape allows them to fit over an inner ring on the case and the bezel fits on the outside. The crystal is compacted between the bezel and case forming a seal. 5. On many pocket watch bezels the crystals are actually friction fit into an undercut in the bezel. This doesn’t provide a water seal but it keeps the crystal in place. 6. Some other acrylic crystals fit inside the bezel. The crystal is compacted with a special tool and its geometry forces it out against the bezel naturally. 7. Still other acrylic crystals are glued in place with G-S crystal cement which is a flexible clear drying glue. This usually used in combination with a crystal that fits tightly within the bezel but the glue provides an additional seal against dust and moisture. 8. An ultraviolet glue can be used to attach a magnifier on a crystal. The ultraviolet glues are formulated to have the same optical properties as the glass and therefore you can see through them perfectly clearly. 9. A few watches have crystal that are integral to the case and not intended to be replaced. This would include Swatch and Rado <-- although the latter can be replaced if you can find a suitable crystal for the job.
I think that about covers it. If you can think of some other way crystals are attached post a comment.
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