The watch crystal is the glass covering the face of the watch, protecting it from dirt and water. There are three major types of crystals used in watchmaking:
Sapphire is the second hardest known element, right after diamonds, making it scratch resistant and useful for watch crystals.
Mineral (glass) crystals have been used for centuries. Easy to scratch, and cannot be buffed out, but are rather inexpensive compared to sapphire.
The most affordable type but also the most prone to scratching (small ones can be buffedw out) and can crack if impacted. Acrylic can be molded into elaborate shapes.
Many modern watches have glow-in-the-dark hands and hour markers. The substances used for this has changed through the years. Here are three of the most notable luminescent paints used in watchmaking over the years:
Discovered by Marie and Pierre Curie in 1898, Radium, other than its use in nuclear medicine, has no commercial applications, though it was once used as a radioactive source for radioluminescent devices. Today, these former applications are no longer in vogue because radium’s toxicity has since become known, and less dangerous isotopes are used instead in radioluminescent devices.
Tritium is a safer radioactive isotope of hydrogen. The emitted electrons from the radioactive decay of small amounts of tritium cause phosphors to glow so as to make self-powered lighting devices called betalights, which are now used in firearm night sights, watches, exit signs, map lights, knives and a variety of other devices.
Strontium aluminate–based non-radioactive and nontoxic photoluminescentor afterglow pigments. This technology offers up to ten times higher brightness than previous zinc sulfide–based materials. Not only that, it lasts longer – as the material does not suffer any practical aging. It has to be protected against contact with water or moisture though, since this degrades the pigment.
An ardillon buckle is a traditional buckle where one end of the watch strap is pulled through a buckle with a pin used to lock it in place.
The deployant buckle is a leather strap or metal bracelet attached to a folding metal buckle. These are more secure than the Ardillon Buckle, because if it unbuckles, it is still on the wrist.
After the clock face there’s no more noticeable part of a watch than the bezel. The look and design can easily make or break a watch. Bezels are more than just for show though. They have practical purposes, evident from the array of numerical patterns commonly seen surrounding a wrist watch face. With that said, nine times out of ten a given watch is chosen for its style, not the need for its bezel function. It’s still good to know the difference between watch bezel types, even if you’re only going to demonstrate the utility for friends.
Watch bezels with Greenwich Mean Time markings are meant to allow the wearer to keep track of time in two time zones.
The complexity of a pilot’s watch bezel isn’t just for show. There’s loads of data to gain from it – if you’re able to do the additional math required, including fuel economy, speed, and rate of descent.
The markings on a diver’s watch are there for matters of life and death – keeping track of available air and also timing ascents to avoid the bends.
Also known as a pulsometer, the medical bezel helps doctors and other healthcare workers determine heart rate.
Move the ring marker to your tee time and the bezel helps to keep the player on target for a roughly four hour game.
Similar to the pilot watch, tachymeter bezels are used mainly to clock distance. The tachymeter bezel can also be used to calculate the speed of just about any moving object.
Once the outer dial is appropriately turned the user can then point the 24-hour hand to the direction of the sun to get a rough idea of where the cardinal points are.