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sapphire crystal watch

Sapphire glass | Watch glass | Watches | Scratches | Polishing | Properties

Sapphire crystal watches or mineral glass as watch glass – Everything you need to know in our test & comparison

You may know it from your own experience with different watch models which you wear or have worn yourself. The value of a watch is often significantly defined by the glass used. If you take a look at the specified features when buying a new wristwatch, you will notice that there are usually two different types of glass, which are installed in individual watch models. We’re talking about sapphire glass and mineral glass or various combinations of the two – but where exactly are the differences and which glass is actually better?

Sapphire glass

With a scratch hardness of 9 on the Mohs scale of the German-Austrian mineralogist Friedrich Mohs, sapphire crystal is close to the optimum hardness level that can be achieved with currently known materials. Only diamond with a reference value of 10 is even harder and immediately represents the upper end of the scale.
This is one of the reasons why many watch connoisseurs nowadays swear by a sapphire crystal watch. Although, strictly speaking, it is made neither of a real sapphire nor of glass. Sapphire glass, which came on the market in the early 1980s, is obtained in its raw form from artificially produced corundum, which is relatively costly to manufacture because several melting steps must be applied at different degrees at different rates to obtain the perfect “sapphire glass.”

The subsequent step of further processing is even more difficult, since for watch glass production the extracted crystals are sawn into many thin “slices”. If you’ve been paying attention, you’ll probably notice that due to the hardness of the glass, it can only be cut with diamond saw blades, and even with this material, it’s not easy to fillet the sapphire, so lots of saw blades get broken, which ultimately explains part of the higher manufacturing costs compared to mineral glass.

You are probably wondering why sapphire crystal is called sapphire crystal and not “corundum crystal”. This question can be answered by the fact that a sapphire is a specific variety of corundum, and the name sapphire is much more commonly used than corundum in the general public.

Unlike real sapphires, which have a light bluish appearance, a man-made sapphire is colorless.
Despite the very good properties of sapphire crystal, it is not indestructible. You should not drop your sapphire crystal wristwatch too often. If the angle is unfavorable, the glass may break because the maximum tensile load cannot withstand the maximum compressive load. The tensile load of sapphire crystal reaches about 1/10 of the maximum compressive load.

In concrete terms, this means that when pressure is applied to the glass from the front, the back is also always subjected to tension. If the tensile load is exceeded, the glass may break. However, this nominal weakness of sapphire crystal also exists in the competitor “mineral crystal”; the maximum tensile strength here is lower than that of sapphire crystal.

Single-sided or double-sided anti-reflective sapphire crystal – Which is better?

Important to know, sapphire crystal in its original form refracts light very strongly, so you should definitely make sure that the sapphire crystal is anti-reflective on one or both sides when buying a watch. Whether single-sided or double-sided is a matter of taste. The advantage of sapphire crystal with anti-reflective coating on one side is that the watch retains its scratch resistance. On the other hand, sapphire crystal with anti-reflective coating on both sides has the advantage of better readability. The scratch resistance decreases on the surface, but you can also grind off the anti-reflective layer on the glass and say adiós to the scratch. In the chapter “What to do if your watch is scratched? Polishing sapphire crystal correctly – care instructions”.

Mineral glass

The perennial favorite among glasses is mineral glass. As the successor to the plastic glass once often used, it scored points from the 1970s as a solid alternative with, among other things, improved scratch resistance. Mineral glass consists of silicon oxide(SiO2), its chemical structure is closely related to that of rock crystal and various other types of quartz. However, in its simple form, it resembles, above all, the well-known window glass.

A good wristwatch relies on tempered mineral glass, which is subjected to a chemical process for the purpose of robustness and scratch resistance, ultimately significantly increasing the resistance in general. (Watchmaker Seiko uses this glass in its wristwatches under the name “Hardlex” – with a Vickers hardness of up to 950).

Mineral glass does not compete with sapphire glass, which is many times harder, even after refinement, especially in terms of scratch resistance. Nevertheless, mineral glass also has some advantages, such as the fact that it is impermeable to water and does not turn yellow, allowing a long-lasting flawless view of the dial.

 

Mineral glass with sapphire coating

As the name suggests, this is a hybrid of the two types of glass. In these cases, it is tempered mineral glass with an extra surface sapphire coating. In contrast to the expensive sapphire glass production, this hybrid combination used to be much cheaper for the producer to manufacture.

The word sapphire crystal in the designation also suggested a higher product quality, although such a coating only has marginal effects on the scratch resistance of such a hybrid glass.

A gif of the various Series 1 watch models of the brand MNMA

Acrylic glass (plexiglass, acrylic glass, hesalite glass)

Acrylic glass, which is also known as Hesalite glass or Plexiglas (both are once trademarked names for this type of glass by watch companies), is once again less expensive to produce than mineral glass. However, it cannot hold a candle to other types of glass in terms of scratch resistance and is therefore rarely used in watches.
One watch brand that partially relies on this glass in their watches is, for example, the German watch manufacturer “Junkers”. (under the name of Hesalite glass)

The advantage or disadvantage, depending on your preference, of acrylic is that it is very light and minor scratches can be polished out relatively easily. The disadvantage of this glass is that it is easily scratched because the scratch resistance is only 500 Vickers.

Gorilla glass as watch glass

Gorilla Glass mainly comes from smartphones. In fact, it does not belong to the classic watch glasses. Recently, however, it has also been used in many smartwatches. It is currently mainly used in smartwatches and fitness watches. Gorilla Glass is made of alkali metal silicate and has improved durability due to an ion exchange process. This creates a certain surface compressive stress and protects the glass from scratches. In addition, the break resistance of Gorilla Glass is 8 times higher than that of conventional (mineral) glass.

Gorilla Glass vs Sapphire Glass Watches

Currently, the hardness and scratch resistance of gorilla glass can not compete with sapphire glass. However, it is constantly being developed further and it can be assumed that gorilla glass will replace sapphire glass in an improved form one day in the next few years. But there is still a long way to go until then.

 

Comparison Table Sapphire Glass vs Mineral Glass vs Gorilla Glass vs Mineral Glass with Sapphire Coating

FeaturesTempered mineral glassSaphire glassSapphire glass - double-sided anti-reflective coatingMineral glass with sapphire coatingGorilla glass
Scratch resistance4/1010/108/105/107/10
Breaking strength (traction)3/108/108/104/106/10
Manufacturing price8/107/106/106/107/10
Refraction /strong>8/105/1010/106/106/10
Overall22/4030/4032/4021/4026/40

Table 1: Shows how many points from 1-10 for each property we think each type of glass deserves.

How can I recognize sapphire crystal?

It is very difficult to tell with the naked eye which glass has been used in a particular wristwatch. If one touches or taps the glass, however, it can be guessed from circumstantial evidence. For example, sapphire crystal is usually slightly colder than mineral crystal at the same room temperature.

Watches water drop test to determine sapphire crystal

Sapphire crystal water test – drop remains compact on right MNMA Series 1 watch compared to mineral crystal watch where drop “smears”

Tapping the watch glass also provides further clues about the installed watch glass; it feels dull with sapphire glass and rather bright with mineral glass.

Another test is to apply a drop of water to the center of the glass of the watch in question. If the drop retains its shape, there is a high probability that sapphire crystal was used. If the drop loses its shape and runs, you can be relatively sure that the wristwatch has mineral glass. See also the picture on the right, we once compared a MNMA Series 1 with real sapphire glass with a watch from another manufacturer, which “only” has mineral glass as installed glass – we find in the comparison, the difference is clearly visible.

It gets a bit more difficult when a special coating has been applied to the upper side of the glass, for example for better readability. Due to the coating, the drop may run despite the installed sapphire crystal, so we recommend the diamond tester method.

The last and safest method is provided by the
Diamond tester*
which is normally used to test gemstones for authenticity. However, it also works for watch glasses. The diamond tester tests the thermal conductivity of the glass. Sapphire glass differs in this respect, as it conducts heat very well, much more than any mineral glass.

To do this, the first step is to heat the tip of the device to a certain number of degrees. The front end of the device is then pressed onto the watch glass, after which the speed at which the tip cools down is measured. The various luminous points on the device show how strong the cooling is on contact and provide information about the thermal conductivity of the respective watch glass. Reliable can be purchased in specialized stores already for a small amount.

Now let’s look at what you can do if there are scratches on the watch.

Diamond Selector II tests whether sapphire crystal has been installed in the watch.

Polishing sapphire crystal correctly – care instructions

A watch is a piece of jewelry and usually not a cheap accessory. Pieces of jewelry need to be taken care of, so that even after some time you do not lose any of its luster.

Proper care for sapphire crystal is an important aspect and should not be neglected. Therefore, despite the degree of hardness, avoid corresponding shocks or friction on your watch. If you still see irregularities on the glass, they are usually other substances disguised as “scratches”. You have the possibility to easily remove these potential “scratches” by buying a commercial eraser.

However, if real scratches do get on the watch, it is difficult – but not impossible – to polish the scratches out again. For the craft professionals among us, it is an advantage to have a
Dremel*
tool is available in the household. Buy in addition Diamond grinding paste* with a 3000 grain and
Polishing felt*
, of course everything at your own risk. If you are appropriately careful and have some time and patience, the sapphire crystal will soon look like new. However, if you do not have any knowledge in this area, it is advisable to go to the craftsman you trust or have the glass replaced by the jeweler.

Important: Some manufacturers install sapphire crystal with an outer anti-reflective layer on the sapphire crystal. This AR layer serves for a better anti-reflection coating. However, this leads one of the main advantages of sapphire crystal ad absurdum, the scratch resistance is lost.

Before buying, you should find out whether your watch has an outer AR layer and whether you would like to keep it if you plan to polish it, since it will be ground off by the diamond grinding paste.

Say goodbye to scratches and get your sapphire crystal watch from MNMA now!

Scratch-resistant, shatterproof & minimalist – from 139 euros ☑

We put an end to annoying scratches on the watch. We install genuine sapphire crystal in our wristwatches for maximum durability.
In addition, each of our watches has at least 5 ATM water resistance, so you can wear it even when showering, for example. The Sony battery inside increases the runtime by up to 12 months compared to a conventional battery. The installed very power-saving Swiss or Japanese quality movements from Ronda or Miyota guarantees the highest precision with perfect runtime. Write to us if you have any questions about us or our watches.

We put all our expertise into the Series 1 to create you a durable watch series at a great price with very good components.

 

 Anzug + schwarze  UhrenkombinationMann im dunklen Anzug mit minimalistischer Uhr
ModellCLASSIC CLEAN
MNMA GHOSTLIGHTMNMA BISCUITMNMA LOOK A LIKE
Price219 Euro
149 Euro139 Euro139 Euro
Watch glassReal sapphire crystal Real sapphire crystalReal sapphire crystalReal sapphire crystal
MovementJapanese Movement from MiyotaSwiss Movement from RondaSwiss Movement from RondaSwiss Movement from Ronda
Case width45 mm42 mm42 mm42 mm
max Case height12 mm7,6 mm7,6 mm7,6 mm
StrapLeatherstrap (Genuine Rindsleather) in black, interchangeable strapMilanaise strap in silver, interchangeable strapLeatherstrap (Genuine Rindsleather) in Mustardyellow, interchangeable strapLeatherstrap (Genuine Rindsleather) in caramel colors, interchangeable strap
Bandwidth22mm22mm22mm22mm
HandsFluorescentFluorescentFluorescentFluorescent
Waterproof10 ATM5 ATM5 ATM5 ATM

The top 3 sapphire crystal watches favorites of the editors

Since we also like other models besides our own watches, here you can find our TOP-3 watch models with real sapphire crystal as an alternative.

4.5 Stars

3. PAUL HEWITT – Black sunray PH-C-BSR-2m

 

The Paul Hewitt brand originates from Oldenburg and has developed from a small startup to a global player by means of e-commerce since its founding year in 2009. The offer includes not only watches, but also jewelry such as bracelets, cell phone chains, necklaces, earrings and rings, with the typical anchor serving as a style-defining element. The watch models combine chic minimalism with a touch of elegance. The model ,,Black Sunray
PH-C-B-SR-2M*
” from the Chrono Line focuses on a dark accent, as it consists of a black leather strap, black dial and black stainless steel case.

Read more

 

Conclusion:
The PH-C-B-BSR-2M* is arobust, well rated sapphire crystal watch without major weaknesses that scores with its water resistance and of course the genuine sapphire crystal at a price of approx189,00 EUR*. Besides the leather strap, the watch is also available with e.g. Mesh strap available.

What we like:

☑ Sapphire crystal
☑ Calendar function
☑ 5 ATM water resistance
☑ Renowned brand movement from RONDA, SEIKO, EPSON or MIYOTA
☑ Stopwatch function

Where do we still see potential:

– Second hand almost as big as minute hand, relatively difficult to read
– narrow hands

4.5 Stars

2. fossil mens chronograph quartz watch fs5384

 

BERING is a Danish jewelry and watch manufacturer, which has purism, excellent workmanship as well as a long life of the watches engraved on its banner. The model ,,Classic – 14240-303* ” also comes in slim design and is equipped with a blue Milaniase bracelet.

Read more

 

Conclusion:
With the Classic – 14240-303* Bering has a hot iron with an icy touch in the fire. We especially like the solid color scheme of the watch and the details that are subtle but placed in the right places. The price for the watch is about
133,80 EUR*
incl. VAT

What we like:

☑ Slim design
☑ Handling
☑ Sapphire crystal

Where do we still see potential:

– 3 ATM
– Unspecified quartz movement
– price

4.5 Stars

1. casio wave ceptor mens wrist watch

 

The watch pioneer
Casio*
with the legendary Wave Ceptor* , is of course also represented in our list. The very popular model comes in silver with a black dial and has an integrated solar function as a special treat.

Read more

 

Conclusion:
A real watch for real men.
Casio lives up to its reputation as a global BigPlayer and gives the
Wave Ceptor*
many good components for the price of approx. 188,10 EUR*. Besides the good components, we also like the available solar function, of course.

What we like:

Hybrid analog digital display
☑ Solar function
☑ 5 ATM water resistance
☑ Sapphire crystal

Where do we still see potential:

– unspecified movement
– price

5.0 stars

Insider Tip:
MNMA Chronographs Sheriff Series

 

Brand: MNMA

The MNMA SHERIFF is the latest model of the company from Germany and combines chronograph look with reduced design. All this is combined with a classy mesh strap and the full range of high-quality components, such as 10 bar water resistance and sapphire crystal.

Read more

 

Conclusion:
A chronograph model as a noble black edition with minimalist design and high quality components at a price point of
229 Euro
. If you want to enjoy your purchase for a long time, you definitely won’t go wrong here and will enjoy your wrist companion. Optionally, the model is also available with individual engraving.

 

What we like:

☑ Japanese chronograph movement Miyota
☑ Doppelt entspiegeltes Saphirglas
☑ Water resistance of 10 ATM
☑ Case size 45mm
☑ Minimalist design

 

Where do we see potential:

➖ Brand still relatively unknown

 

soeren_lenzner_gruender_MNMA_Uhren

Soeren, founder of MNMA

My conclusion in the watch glass comparison

 

Both wristwatches with mineral glass and sapphire glass have their raison d’être. Buyers who value maximum durability, scratch resistance and the look & feel of a wristwatch will be happy with a sapphire crystal watch.

If price is the main consideration for a wristwatch, mineral glass is a sensible choice to keep the overall price down, as manufacturing is at a cheaper level.

You should not necessarily bet on a watch with acrylic glass, unless the purchase price is less than 40 euros.

With the other properties of mineral glass, the price-conscious buyer definitely gets a solid glass base for his wristwatch, but in case of doubt, he has to reckon with a new purchase rather than if a higher-quality glass is installed.

The mixed combinations of the two glasses are not recommended nowadays, in our opinion, because the production is expensive and the production costs of sapphire glass have decreased. Which largely offsets the former advantages.

Much more reading material is available from us in the form of guidebook articles:

Looked in:

The links marked with an asterisk (*) are so-called affiliate links. If you click on such an affiliate link and make a purchase via this link, I will receive a commission from the online store or provider in question. For you, the price does not change.

Letzte Aktualisierung am 2022-09-25 / Affiliate Links / Bilder von der Amazon Product Advertising API

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