Sapphire crystal or mineral glass in a watch?

Of course it is a shame if the surface of the watch gets scratched. Other people might not even notice it, but it might bother you when you are aware of it. We at Rohje have aimed to make the watch one that won’t get scratched at all. That’s why we focus on details.

Most commonly the glass of watches are made out of mineral glass or sapphire glass. Sometimes even acrylic, meaning plastic.

We find sapphire crystal, meaning sapphire glass serves Rohje watches the best. Next I’ll explain why.

Sapphire glass, is made synthetically and isn’t actually considered a glass but a crystal. The sapphire crystal is made in very high temperatures and it made up from crystalline aluminium oxides. These are then cut with diamond saws, grinded and polished to the finished “glass” product. Sapphire crystal can sustain scratches very well and it can only be scratched with materials, basically diamonds and especially hard rock types.

Mineral glass, which is usually a common watch glass is scratched more easily, but it can take hits better.  The same way acrylic glass, meaning a “glass” made of plastic, can take hits because of its flexibility, but is scratched very easily.

We see that being able to be scratched and being able to take impacts are opposite qualities. The harder and less likely to be scratched the glass is, the less it can take impacts. Hardness is measured with the Mohs scale of mineral hardness from 1 to 10.

Diamond is the most hard with its value of 10, it can scratch all other minerals. Mineral glass is around 5-6 and acrylic around 3. The Rohje Sapphire crystal is 8-9 on the Mohs scale, being nearly unscratchable.

We have focused on the chosen sapphire crystals details. The reflection given out by the sapphire glass can be diminished by adding the smallest anti-reflection coating. That’s why the colour of the face our Adventurister Dark watch models can be seen turning a tiny amount blue when looked from a specific angle.

The glass of the Rohje Adventurister watch is coated with this anti-reflective coating. The glass could be treated from both sides, but the outside coating could wear of and make the glass splotchy. We want our watches to work, but also look good for a long time, so that is why we ended up coating only the inside of the glass.

The details are very important. Go check the other features of our watch.