What Are Watch Crystals Made Of

There are thousands of different watches, made by many brands, in all shapes and sizes. The one thing that they all have in common is that they have a crystal, or glass, covering the face of the watch. The crystal serves a very important purpose: it protects the watch face from damage. Along with the crown and the case construction, it is also responsible for making the watch dustproof and help with water resistance. Sometimes you will see a little extra ball of glass on top of the watch crystal. These are called “Cyclops”, and are used to magnify something on the watch face, usually the date. There are a variety of different materials that are used for watch crystals, and this blog post will explore the three main ones: plastic, mineral and sapphire.

What Does The Watch Crystal Do?

Simply, the watch crystal protects the watch face from any damage that it might suffer. This could be scratches and bashes picked up when you wear the watch, or it could be from dust or water. In some instances, the watch crystal is covered in an anti-reflection or anti-glare coating. This means that you can read the time when it is very bright, or when you are underwater.

Plastic, Acrylic, Plexiglass or Hesalite Watch Crystal

Most watches are fitted with plastic crystals. You might see a watch crystal described as Acrylic, Hesalite or Plexiglass. These are all just names for plastic watch crystals. Plastic is the cheapest watch crystal to manufacture and to replace if it breaks. Plastic has been used to make watch crystals since the 1920’s, and many vintage watches are more desirable to collectors if they still have their original plastic crystal. You might see vintage Rolex watches described as having their original ‘Plexiglass’, or vintage Omega ‘Hesalite’ Speedmasters. This just means they still have the plastic crystal that they were originally supplied with.

Plastic scratches easily, which might be seen as a disadvantage; however, these scratches can be polished out at home. The material is also more flexible, which means it cracks, rather than shatters. This is means it is very good for children’s watches. It is also why it was used on the Omega Speedmaster when it went into space. NASA felt it was safer for astronauts to have watch faces that crack, rather than splinter. Small shards of glass would be very dangerous in zero gravity! If you want to learn more about the watch crystals used on the Omega Speedmaster,  here is a great article.

Plastic is very easy to shape, so it can be made thicker to better protect the watch. The plastic crystal on the watch below is thick, but curves into the bezel so it still looks elegant. This would be very expensive to do with mineral or sapphire glass.

Mineral Watch Crystal

Mineral watch crystal is the mid-point in terms of price and quality. It costs more and is harder than plastic but costs less and is less hard than sapphire. Many watches with mineral glass also have an antireflective coating. Mineral watch glass is simply toughened glass. It is made by heating the surface to make it harder and less likely to shatter. It will still get scratches, chips and occasionally shatter. If you get a scratch or chip on a mineral watch crystal, you will need to send it back to the manufacturer to see if they can buff it out. It is more likely that they will need to replace the crystal.

Sapphire Watch Crystal

Sapphire watch crystals are the most expensive and hard wearing. Many luxury watches will have a sapphire crystal on the front of the watch. They might also have them instead of a metal caseback, so that you can see the movement. Some expensive watch brands use this to highlight the craftsmanship that goes into ‘finishing’ a movement (making it look nice). You’ll see what a sapphire caseback looks like in the picture below. Most Sapphire watch crystals are actually made of synthetic sapphire. This is created by heating Aluminium Oxide to very high temperatures, then pressing it together very hard. Disks are then sliced out of it and polished with diamond coated saws.

Natural and man-made sapphire is one of the hardest materials on earth, so it is very expensive to work with. This explains the high cost of sapphire watch crystals. It is verydifficult to scratch or damage sapphire watch crystals. You can only do so if you hit the crystal on something that is as hard as diamond. There aren’t many things that hard! Some ultra-expensive watches now have cases made entirely out of sapphire crystal as well. The Richard Mille Sapphire RM 56-02 Tourbillon Sapphire is one example.

Conclusion

We at The Watch Collectors’ Club own watches with all types of crystal. We don’t think there is a best watch crystal. Some watches suit a sapphire crystal, others work best with acrylic. Part of the fun of collecting something is finding what you like best for your budget. We hope this post will encourage you to explore more of the features of your watch. Don’t forget to check out the rest of our blog posts, our Instagram and Facebook (links below).

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