The watch crystal is the clear covering that sits over the watch face. It houses the watch hands and usually the edges are covered by the bezel. The crystal will more often than not fit inside the watch case, although this doesn’t mean that the case or bezel is holding down the crystal.
What’s important about the watch crystal is that it is a hard surface and that is fairly resistant to scratches, although it can scratch, chip and get scuffed over time. Also, it is important that the crystal is secure because it protects the face of the watch from water and dirt and other environmental influences that your watch can come in contact with.
Different Types of Watch Crystals
Synthetic Sapphire: This transparent, lab grown element has exactly the same chemical composition as natural sapphire. Sapphire ranks a 9 on Mohs’ hardness scale. It is the most expensive type of crystal and the majority of watches imported from Switzerland contain them.
Mineral: Mineral crystals are made of glass. Mineral crystals are a 7 on the Mohs scale of hardness. They are inexpensive compared to sapphire crystals, usually costing less than one hundred dollars to replace if damaged.
Acrylic: Acrylic is the most affordable type of crystal. It can be easily polished to remove light scuffs.
Anti-Reflective or Anti-Glare: This type of crystal has been coated on one or both sides with a substance – the same one used on anti-reflective eyeglasses – that lessens reflections and glare and makes it easier to read the watch face. Anti-reflective crystals can be made of either mineral glass or synthetic sapphire. Viewed from the front, they are virtually invisible because they aren’t reflecting any light. In some instances, the coating gives the crystal a telltale bluish tint, as it does on eyeglasses. This tint is easiest to see if the watch has a light-colored dial.
Watch Crystal Factoids
- Most pocket watches use a low dome crystal.
- Most wrist watches use a high dome crystal.
- Rolex Crystals need to be fitted by Case number. This number can be found, between the lugs at the 12 o’clock position.
- Omega Watches that are fitted for crystals require their case number located on the inside of the case back.
- The watch crystal can be installed either with a crystal life or glued in.
- To fit a watch crystal with a bezel with a crystal life, the crystal will need to be the next size up or in this example 22.3 so it will be 1/10th larger.
- If the watch crystal is glued in it will require the crystal to be the same size as the measurement or a tenth of a millimeter smaller.
- Mineral Glass crystals are sold in thicknesses of 1.00 mm, 1.5 mm, 2.0 mm, 2.5 mm and 3.0 mm.
- Most all pocket watches today are fitted with plastic crystals.
- Mineral glass and sapphire generally look the same.
- A stainless steel knife or screwdriver will scratch a mineral-glass crystal but not a sapphire one.