While other features of a watch, such as the movement or the complications, are often discussed, one component is often treated somewhat stepmotherly: the watch glass. We would like to change that with this article! The following is all about watch glasses and what differentiates the various watch glass materials.
The importance of watch glasses: Why they offer more than just protection
Glass is an indispensable part of any watch. It protects the dial, including the hands, from dust and dirt, keeps water out, and offers protection to sensitive components from direct contact. Through the glass, the time can be read optimally, and the clarity and transparency will not be dimmed for decades with a high-quality watch glass that has been treated with care. However, even if the glass of a wristwatch primarily serves purely practical purposes, its influence on the appearance of a timepiece should not be underestimated. An undamaged watch glass with a chic curvature can look absolutely noble, ensure that the dial is ideally displayed, and thus significantly influence the appearance of a watch.
Sapphire crystal
Sapphire crystal has been used in wristwatches since the 1980s. This is artificially manufactured sapphire - a material that is characterized by its hardness and resistance. Today, the synthetically produced glass enhances numerous brand watches and contributes to their proud price. This is because the production of sapphire crystal is comparatively complex, which drives up the cost. This is why sapphire crystal, which has a hardness of 9 Mohs and is therefore almost as hard as a diamond, is mainly found on the exquisite dials of luxury watches.
Mineral glass
With mineral glasses, a distinction must be made between untreated and hardened glasses. Untreated mineral glass is equivalent to window glass. Such mineral glass is comparatively easily damaged, because although it is much harder than plastic, it is still quite susceptible to scratches and is not immune to breakage under higher stress. The mineral glass can be hardened by a chemical process, which makes the watch glasses much more robust.
Plastic glass
The plastic glass is the lightweight among the glasses for watches. Often referred to as Hesalite glass, Plexiglas or acrylic glass, plastic glasses have amazing impact resistance, but also low density. This means that they are quite soft - especially in comparison with glasses made of sapphire - and, accordingly, quickly get a scratch.
Advantages and disadvantages of watch glasses
All common types of watch glasses have their advantages and disadvantages. We would like to clearly compare these at this point to create a direct comparison.
Regarding the hardness of the materials already described, sapphire stands out particularly positively. Traces on the hard glass are often not scratches, but merely abrasions that have gotten onto the glass from the outside due to contact with softer materials. These can be easily removed. The situation is different with plastic lenses: they scratch comparatively quickly, but are easy to polish, which means that removing fine scratches is usually no problem. In terms of hardness, mineral glasses are in the golden mean. Mineral glass is more scratch resistant than plastic glass, but more demanding in polishing. If watch crystals made of mineral glass break, the possibility of fine fragments penetrating the movement cannot be ruled out. In the worst case, this can result in serious damage to the movement. It is precisely this risk that is reduced by the hardening treatment of the glass.
The clear advantage of the plastic watch crystal: it is wonderfully light and does not reflect. Exactly here lies a disadvantage of the sapphire crystal. This is known for strong light refraction and associated reflections, which can significantly disturb the view of the watch depending on the incidence of light. To counteract this, it is not uncommon for special coatings to be applied to the glass, which can seriously reduce the reflection. In return, sapphire and mineral glass remain absolutely clear for many years and decades with proper care, while lower-quality plastic watch glass can become cloudy and yellow under certain circumstances. Among other things, this is due to the effect of UV radiation on the material.
Another distinguishing feature: Glasses made of plastic have an osmotic property. This means that they are not necessarily absolutely impermeable to water. For this reason, they are usually reinforced in diving watches and are usually used in particularly thick forms. In contrast, watch glasses made of sapphire glass and mineral glass are not osmotic.
How to recognize the best watch glass?
Which material is best for watch crystals ultimately depends to a considerable extent on the wearer's individual ideas. After all, all cleanly finished watch glasses offer protection against dust and the like and thus fulfill their main purpose. When choosing a watch crystal, however, several important aspects should be considered. First and foremost, you should consider in advance which features and characteristics are particularly important to you personally. For example, if you want a very light watch glass, plastic glasses are the best choice. If, on the other hand, you attach great importance to resistance and a touch of luxury, the decision in favor of sapphire crystal is obvious.
In any case, it is essential to obtain detailed information and, if necessary, professional advice. After all, all watch glasses have their pluses and minuses, which you should know before making a purchase in order to make the best choice.
Conclusion
From Plexiglas to mineral glass to sapphire glass, various proven materials are used in watches today. Which watch glass is best suited in a particular case is sometimes determined by the priorities of the wearer, the budget and the planned use of the watches. In any case, it is worthwhile to take a close look at the exciting topic of watch glasses in order to be able to correctly classify the features that distinguish the options from one another and keep them in mind when buying a watch.