About Watch Glass

The watch glass protects against dirt and damage-logically the dial and the delicate hands! But what types of watch are there and what are the specific Properties and advantages and disadvantages? What are the common antireflection coatings of watch glasses?

These and more questions are answered in this detailed article about watch glasses.

Types of watch glass: Sapphire glass, plastic glass, mineral glass, Hardlex

The types of Crystal Sapphire Crystal, mineral glass, plastic glass (Hesalith, acrylic or plexi) and Hardlex glass can be characterized primarily based on four properties : scratch sensitivity, care facilities, mirroring and costs.

Without great speeches, I have assessed the respective characteristics of the watch glass types in a compact matrix:

Even if it doesn’t look at first glance, is The Nonplus ultra in watch Sapphire Crystal: It is almost unzerkratzbar- in the everyday life of Otto normal of watch fans can actually only concrete have something the sapphire glass (but the least will have to do well every day with diamonds diamond,  ). The downside: Sapphire glass breaks the light relatively stark – the watchglass acts this Milky, which can affect the readability.

The production of Sapphire is also quite expensive, and expensive. For this reason Sapphire Crystal is from €300 generally in clock models used. A cheap entry level model with sapphire glass is for example LACO B pattern observation watch model “Faro”, which I have tested. Of course also watch manufacturers use only Sapphire Crystal in the high-end segment like Rolex, Omega, Breitling and TAG Heuer.

Breitling writes regarding the manufacturing process of Sapphire:

The synthetic sapphire is made on the basis of alumina (aluminium oxide). The merger takes place at 2050 ° C in the presence of hydrogen and oxygen. Same so-called creamy PEAR, a corundum (crystallized alumina) forms a stalagmite to the base after around 15 hours a. The stones then again at 1800 ° C are heated to the stabilization of matter. Diamond blade saw the corundum then sliced. The glass on the desired diameter is cut with an accuracy of 2 Hundertstelmillimetern, followed by the glass thickness the surface treatment, so grinding. Grinding of front and back glass gives the domed shape.

And looks like the rather impressive production of Sapphire in the Breitling home:

Mineral glass is used, however, mainly in very low clock models under €100 : chemically considered it comes very close to window glass and is very cheap in the making. An advantage is also that mineral glass, not so strong like Sapphire breaks the light.

The biggest disadvantage of mineral glass is but very clear low hardness: unsightly scratches, which are also can be removed by polishing or similar, therefore with minor bumps appear. Here an unsightly example of my fossil watch, who has cuddled our front door:

Good to know: probably only höherpreisigere watch brand the fledgling company Sevenfriday relies almost exclusively on mineral glass – and that at prices starting at about €1000! That is the criterion for exclusion number 1for me personally just, as also the extremely independent and unique design of watches helps nothing.

Hardlex glass it is basically just a refined mineral glass, which in addition is hardened, to make it more scratch-resistant. Of course relatively unsexy sounds, which is why the Japanese watch maker Seiko introduced the name Hardlex. Also other manufacturers harden the built-up mineral glass, such as Swiss military Hanowa or Festina-the quality of hardening should vary quite sharply however, depending on the manufacturer. Models cost usually less than €200 with tempered mineral glass.

Scratches on the watch? Easy plastic glass polishing…

Plastic glass is light, cheap production and hardly reflects. It is very soft plastic glass and accordingly vulnerable to scratches (anyone who ever had cheap picture frames from IKEA in hand, know what I speech).But I would personally prefer plastic glass always mineral glass: That is the Vintage charm of plastic glasses, because the lens warmer than Sapphire or mineral glass comes across. Also, finer scratches can be relatively easily, E.g. use Polywatch to remove from plastic glass. For deeper scratches, but also an Exchange is not difficult and particularly wallet friendly.

Probably by far most popular watch model with plastic glass (more precisely: hesalite Crystal) which isOmega Speedmaster Moonwatch: this is still made almost exactly the same as when the moon landing in 1969, when Neil Armstrong Astronauten-Kollege Buzz Aldrin ventured his first steps.

A bargain is the Omega Speedmaster Moonwatch despite however not plastic glass: the EIA is now proud €4300 after some price increases, the model is available with good discounts on the Internet but, E.g. Watch instinct (CA. €3200). For a juicy premium, but can the Omega Speedmaster Moonwatch buy also in the version with Sapphire Crystal. Cost: €3750 (As of November 2016). Ultimately, the choice of the watchglass is matter of taste–the vintage character of this classic one but of course only with the plastic glass version begins a. This is also the great implemented curvature of the glass, which-suit reminiscent of the model –a planet.

Cambered (domed) Sapphire is incidentally, generally rather in high-priced watches used, as additional production steps (grinding, milling) are necessary, of course driving the costs. Current sample models are Oris divers sixty five, the rock hard Ocean one vintage chronograph as well as the Tudor Heritage Black Bay(here in a variety of bronze).

What are the three examples: domed watch glass is often used around the vintage charm of certain models to underline: In the case of Oris, the first divers watch model from the 60s, in the case of Tudor was taken a model from the 50s as a template and the domed Sapphire Crystal and other details faithfully reprinted. Also the model Ocean one vintage chronograph by a tribute to the outrageously expensive vintage Rolex Daytona “Paul Newman” is rock hard.

Anti-reflective coating: Double-sided anti-reflective Crystal – per and versus

In particular anti-reflective Sapphire Crystal is often, to counteract the disadvantage of strong light refraction.This is a chemically metallized layerthat is evaporated on either only on the inside page of the watchglass oron both sides .

The usual way, the producers go, is an antireflection coating of the inside of the Sapphire Crystal. Because: An anti-reflective coating layer is softer and softer as the sapphire glass itself and therefore scratch-prone. At first glance, the anti-reflective coating of the outside is so actually complete nonsense because Yes the biggest advantage will be shortened by Sapphire Crystal – scratch resistance -.

Nevertheless, many manufacturers put on it: for example, (almost) all current models by Breitling, sense, Hanhart, Union Glashütte and many models of Omega set on a double-sided anti-reflective coating. And that has a simple reason: the readability of the watch is extremely increased, depending on the angle of view is even the feeling that is not even a watch glass available . In combination with a high-quality dial is effect in my opinion simply terrific and greatly enhances the optics.

The anti-reflection coating layers are now partially also so highly valued that hardening to the 1800 HV be achieved, at least roughly corresponding to Sapphire Crystal. In case of doubt you should contact the manufacturer, the hardness of the outer layer of anti-reflective coating has (measured in HV hardness Vickers). Here are a few HV reference values of MEANING:

Examples for hardening:
Stainless steel: about 200 to 240 HV
Titanium grade 2: approximately 210 HV
Titanium grade 5: about 350 HV
Hardened mineral glass: approximately 800 to 900 HV
Sapphire Crystal glass: about 2,000 HV
Diamond: > 4,500 to 10,000 HV

The anti-reflection layer can have also a characteristic colour shimmer depending on the viewing angle. Current Breitling models E.g. usually have a bluish glow on the watch. Is this good to see:

Exactly this bluish shimmer on the watch is often criticized. Personally, I like it – just a matter of taste!

Breitling describes the in-house anti-reflective coating procedures as:

After the necessary for the adjustment in the housing bevelling of the edges, the glass is polished on both sides chemically. It now enters a sterile laboratory (white space), where there is anti-reflective by vacuum evaporation in an oven. This double-sided treatment eliminates 99% of reflexes that is perceived by the eye.

Omega is on the other side on a colorless layer of anti-reflective coating:

Interestingly enough is Rolex in many models even no anti-reflective coating (except when the date Magnifier). “Built to last” seems to be the creed that the customer should be spared even after many years of scratches. However, that doesn’t explain why Rolex for many models anti-reflective not at least the inside of the watch glasses.

With classics such as the Rolex Submariner , the reason however may be a fairly simple: as with the Omega Speedmaster Moonwatch wants to stay close just on the original model presented in the year 1953, which was obviously not antireflective coating. However is why hot discussions among watch fans. The tenor: A little bling-bling through the reflective sapphire glass belong to probably just to a Rolex…

Although I as I said am fan of double-sided anti-reflective Crystal, so I must break but a lance for the Rolex Submariner (reference 114060), where the Crystal is not coated at all: the overall look is very consistent through the glossy bezel in combination with the very soft light refraction on the thick Sapphire Crystal. Also the readability is hardly limited to the simple dial design:

Harmonious overall picture: the shiny ceramic bezel and the reflective Sapphire Crystal of the Rolex Submariner

All in all must decide every man for themselves of course whether you like it or not have necessarily anti-reflective Sapphire Crystal. Would you necessarily have his desire clock with double-sided anti-reflective coating, the selection is limited this of course quite strongly, because the majority of watch manufacturers clearly opts for the anti-reflective coating the inside. That not enough who can be his watch but alsos ubsequently (on both sides) entspiegeln for ASABE rule watch technology. This is also an option for clocks, their anti-reflective coating layer is scratched because it removes the old anti-reflective coating layer in front of the new coating over the years. February 2016 booth costs, including installation were fair €85…