Types Of Watch Glass

The term watch glass refers to the transparent covering over the face of a watch. There are a number of different materials that are used to make watch glasses. They are generally made of one of three common materials depending on the make, uses and quality of each particular watch. Each material has it's own advantages and disadvantages, so it is worth understanding the differences. Sometimes the glass is referred to as the crystal, this is not to be confused with the quartz crystal inside of a lot of watches which regulates the timekeeping.

Acrylic Glass
The cheapest glass is actually a plastic. Acrylic plastic is tough, flexible and transparent. It is not likely to shatter as it is very light. The downside is that it may scratch easily. The scratches can be removed, it is advisable to consult a jeweller about the best way to proceed. Childrens' watches often have an acrylic glass as they are unlikely to be able to break it even if they are not as careful as they could be! 

Mineral Glass
The most common form of glass is mineral glass. This is made by using heat or chemicals to treat ordinary glass in order to make it more scratch resistant. If the glass does become too scratched it will need to be replaced.  Unfortunately this also has the affect of making the glass more likely to shatter. Occasionally when a watch glass shatters small shards of glass can lodge themselves into the workings. If this happens then the cost of repair is likely to exceed the value of the watch. Most watches, however, do not end their life in this way; so there is no need to be unduly worried. But it is worth being careful if your watch glass does shatter in order to prevent this from happening.

Sapphire Crystal
The most desirable watch glasses are made out of either synthetic or genuine sapphire. Commonly synthetic sapphire is used. This is made out of crystalised aluminum oxide, it has the same physical properties as the natural gem frequently used in jewellery but without the colouring. It is the most expensive way to create a watch glass but the advantage is that the glass is incredibly durable. Sapphire rates 9 on the Moh scale, (that is the scale that measures the relative hardness of all materials) and is just behind diamond which measures 10. Of all the glasses it is the least likely to shatter or be scratched. If anything you should be more concerned that your watch may scratch another surface! Sapphire crystal is one of the features that pushes up the price of high end watches. This is due to the value of sapphire and partly because expensive tools that use diamonds to cut and shape the sapphire have to be used to make them. Premier brands such as Seiko and Citizen watches often use sapphire glass for their watches.