Many of our customers with older Rolex watches ask if we can replace their acrylic crystals with synthetic sapphire crystals, like the ones that Rolex uses on their new watches. Although every watch in Rolex’s current catalog is now fitted with a sapphire crystal, Rolex does not manufacture sapphire crystals for use on older watches. Instead, they will only replace a worn or damaged acrylic crystal with another acrylic crystal.
The shape of the crystal is different…
The outer diameter is the exact same on comparable acrylic and sapphire crystals. However, quite literally every other aspect of the two crystals is different, including the actual shape of the parts themselves.
Acrylic crystals are made from a single piece of polymer that (more-or-less) has the shape of an upside-down bowl or dish. The “surface” of the crystal is like the bottom of the bowl, while the “sides” of the bowl are the part of the crystal that sits under the bezel and holds it down onto the watch.
Synthetic sapphire crystals are flat and shaped like a disc, similar to the overall size and shape of a coin. Running along the outer edge of the sapphire disc is a groove onto which a specialized, polymer gasket gets attached. The gasket takes the position of the “sides” of the crystal and sits underneath the bezel, holding the sapphire portion onto the watch.
With the specialized, polymer gasket on the crystal, the shape of the synthetic sapphire crystal becomes very similar to the “upside-down bowl” shape of the acrylic crystal.
This gives many people the false impression that – since the two crystals have the same diameter – you can install a sapphire crystal on an older watch that uses an acrylic crystal.
Despite attaching to the watch in a similar fashion, the amount of space on the underside surfaces of the two crystals is slightly different. In some instances, this difference will not provide enough clearance for the hands.
The bezel is also different…
Additionally, the height of the bezels fitted to watches with sapphire and acrylic crystals is slightly different. While minor, this difference is just enough to create functional issues if the correct type of crystal is not used. Watches designed to use sapphire crystals have slightly taller/thicker bezels. The additional height is needed to hold onto the polymer gasket and keep the sapphire portion secured to the watch.
Acrylic crystals are made from a single piece of polymer and do not have a separate gasket to hold them onto the watch. Consequently, their bezels can be thinner, since they are making direct contact with the base of the crystal itself.