Examining the fine details of a watch yields some interesting information about the components. When one becomes familiar with the various parts it becomes apparent that most brands default to certain materials because they find merit in their properties that fit in with the personality of the watches designed. Have you noticed that the lenses or crystals that are used to protect the dials vary in their composition? Some brands regularly use sapphire crystals or mineral crystals. Another popular lens type is called Hesalite, but what is it and how is it used in watchmaking? To answer the question, here is everything you need to know about Hesalite and its properties.
What is Hesalite?
According to Millenary Watches, Hesalite is a type of plastic material that is transparent. it is an advanced acrylic substance that is known for providing optical clarity while providing durability and a stiff surface that holds its shape well when it is properly formed. Hesalite is also referred to as plexiglass. It was used as far back as the 1840s. It is a man-made material that was used to make contact lenses and other products. It is a material that has been used to cover the dials of watches for more than 160 years.
How is Hesalite used in watches?
Hesalite is a type of crystal that is less common in watchmaking than mineral crystals or sapphire crystals. Some watchmakers prefer the scratch resistance offered by sapphire crystals but this material is not shatterproof. Although it doesn’t scratch easily, its resistance to impacts is not as effective as Hesalite crystals, according to the Swiss Watch Expo. Hesalite crystals were used in the Omega Speedmaster moon watch. In the original, it was the best option because of its shatter resistance. In space, the potential of the sapphire crystal to shatter and send shards into a weightless environment was a risk that could not be taken. This is the main reason why the original MoonWatch featured a Hesalite crystal. If hit with a hard impact, the worst thing that would happen would be the development of a crack. The plastic behaves differently than the glass of a sapphire crystal. This is why it became the crystal lens of choice when developing watches for NASA and the Apollo space program.
The pros and cons of Hesalite
Hesalite is a type of clear covering that makes it a good option for watch coverings. However, if the material was perfect it would be the only material used for making watch crystals. Since it does have advantages and disadvantages it is used in the production of some, but not all watches that are manufactured. Here are the plusses and minuses of Hesalite in its applications for dial covers in watchmaking.
Advantages of Hesalite
Hesalite is an acrylic that is known for its strength and durability. It is highly resistant to shattering, which makes it the best choice when worn in environments and situations where impacts on the wrist could be catastrophic. If a watch crystal does need to be replaced, Hesalite crystals are less expensive, providing an economic advantage if replacement is necessary. Watchmakers can also keep the cost of a timepiece lower by using Hesalite instead of a more expensive sapphire crystal. If a Hesalite crystal becomes scratched, any light marks that are not too deep may be polished out of a watch crystal.
Disadvantages of Hesalite
Hesalite does have its drawbacks. Although this material is not prone to shattering, it does scratch more easily than sapphire or glass. Deep scratches are difficult to buff out of a Hesalite crystal. Using abrasives to polish scratches out of the surface can result in permanent damage to the surface and cause the surface to become blurry. This can make it difficult to have a clear view of the watch dial beneath.
Which is better: Hesalite vs Sapphire Crystal?
Sapphire crystal is created when minerals called corundum are used in a laboratory to create a crystal. It is manmade from natural ingredients that come from the earth. The advantage of the sapphire crystal is that it is four times harder than acrylic crystals such as Hesalite. It is the second hardest mineral on earth, only surpassed by a genuine diamond. Sapphire crystals are more resistant to scratching and these two factors give sapphire crystals the advantage over Hesalite crystals. There are drawbacks to sapphire crystals, however. Sapphire crystal requires cutting into the desired shape. Sapphire crystals can not be made into watch crystals as easily asmHesalite. This feature makes it more expensive to work with. While the hardness can be an advantage, in some situations, it becomes a disadvantage. Sapphire crystal is more prone to shattering when it is hit with a high impact. These are the reasons why the Apollo team chose watches with Hesalite crystals over sapphire crystals. It is safer for space travel.
Do all MoonWatches come with Hesalite crystals?
Not all MoonWatch models are made with Hesalite crystals. There are quite a few variants that feature either glass or sapphire crystal lenses. The type of dial covering used is a matter of the personal preference of the watchmaker and the consumer. If you want a moon watch and you’re not planning to travel outside of the atmosphere, a sapphire crystal is as beneficial as a Hesalite type.
Final thoughts
Hesalite is a transparent material that is acrylic. It is less expensive than sapphire crystals. It is more resistant to shattering. It’s easy to form into various shapes then retain them well. When properly cared for it is clear and legible, offering a good view of the dial beneath. It is, however, prone to scratching, which is the downside of Hesalite. It’s the kind of crystal used when the threat of breaking crystals could be detrimental in case of high impacts that could shatter glass or sapphire crystal. It’s the preferred type of lens for space travel, but it’s not a perfect substance.
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