The difference between mineral crystal, sapphire crystal and acrylic, and which glass is suitable for your watch.

Types of Watch Glasses - A professional guide for proper selection and watch maintenance

When choosing a watch, most of the attention is given to the design, brand, or mechanism. However, one of the most important components – and sometimes the least known – is the glass that protects the watch face. The type of glass affects scratch resistance, transparency, weight, and even the watch's price.

In this article, we will review the three main types of watch glasses: acrylic (reinforced plastic), mineral crystal, and sapphire crystal. We will understand the advantages and disadvantages of each, touch on the history and development of materials, and provide important tips for long-term glass maintenance.

What is crystal glass in watches - Historical and developmental overview:

Acrylic Crystal

Acrylic, also known as "reinforced plastic," was the first material to be widely used in wristwatches starting in the 1940s and 1950s. During this period, it was important for manufacturers to reduce costs and enable mass production, and acrylic was an ideal solution: a lightweight, inexpensive, easy-to-process, and relatively flexible material that was resistant to breakage.

Many vintage watches still feature acrylic crystals today, and they are considered part of the historical authenticity of those models. The main disadvantage is very high sensitivity to scratches. However, the advantage is that they can be polished relatively easily and restored to a new appearance.

Mineral Crystal

In the 1970s and 1980s, with the rising demand for more durable watches, manufacturers began using mineral crystal glass – glass that undergoes thermal strengthening in a unique process that hardens its surface. The result was a much more durable material than before, which managed to maintain a balance between an accessible price and good durability.

Mineral crystal became the standard in fashion watches and watches in the mid-price ranges. It is still a material that can be scratched, but it requires contact with harder metals or stones. In terms of maintenance – it is very difficult to polish scratches, so in most cases of damage, the glass is simply replaced.

Sapphire Crystal

The next stage in development was sapphire crystal glass – a material made from synthetic sapphire (laboratory-grown corundum) and first recognized as the pinnacle of luxury in the 1980s in European luxury watches. Sapphire crystal is considered the second hardest material after diamond, and therefore it is almost impossible to scratch. Its great advantages are high transparency and durability over many years.

Today, almost every luxury watch comes with sapphire crystal, sometimes even in double layers with an anti-reflective coating. Its only disadvantages are its high price and the fact that it is less flexible and therefore can crack from a strong impact.

Why is watch glass so important?

Protection of dial and movement - The glass prevents dust, moisture, and contamination from entering the delicate movement.

Maintaining appearance - High-quality glass prevents scratches and distortions, so the watch looks new for a long time.

User experience - The level of transparency and material quality affect time readability in daylight or low light conditions.

Watch value - Luxury watches almost always come with sapphire crystal glass, which increases their value.

Acrylic Crystal

Features:

Essentially a type of reinforced plastic.

Was very common in watches from the 1950s to the 1980s.

Still appears in some inexpensive watches and certain vintage models.

Advantages:

Inexpensive to produce – reduces the watch's price.

Relatively light – suitable for children's watches or simple sports watches.

Somewhat flexible – less prone to breaking from an impact.

Disadvantages:

Scratches very easily.

Tends to yellow over time.

Less luxurious – perceived as a cheap material.

Mineral Crystal

Features:

Glass that has undergone a thermal strengthening process.

Most common today in fashion watches and mid-range priced watches.

Advantages:

Good scratch resistance compared to acrylic.

Significantly cheaper than sapphire crystal.

Relatively light.

Can be coated with an anti-reflective coating for improved transparency.

Disadvantages:

Can still be scratched (especially by keys, metals, or stones).

Less durable over years compared to sapphire crystal.

Very difficult to repair scratches – usually requires glass replacement.

Sapphire Crystal

Features:

Made of synthetic sapphire (lab-grown corundum), one of the hardest materials in the world.

Considered the highest standard in luxury watches and professional dive watches.

Advantages:

Almost absolute scratch resistance – only a diamond can scratch sapphire.

Excellent transparency, especially with an anti-reflective coating.

Luxurious appearance and quality feel.

Disadvantages:

Very high price.

High rigidity – can break from a strong impact (unlike acrylic which is more flexible).

Almost impossible to polish or repair – usually requires replacement.

Comparison between the types

Glass Type Scratch Resistance Price Impact Resistance Appearance

Acrylic Very Low Cheap Good Basic

Mineral Medium Medium Medium Quality

Sapphire Very High Expensive Low (may break) Luxurious

Historical Development

1950s-70s - Most watches used acrylic. Cheap, easy to produce, suitable for the masses.

1980s-90s - Introduction of mineral crystal, offering a good balance between price and durability.

Recent Decades - Rise of sapphire crystal as the standard in luxury watches, alongside continued use of mineral for more accessible fashion watches.

Colors and Finishes

Most glasses are completely transparent.

Versions with anti-reflective coating are available - prevents glare in sunlight.

Some watches feature domed glass that gives a vintage look.

Colored glasses (blue, green) - rare, but appear in unique watches or limited editions.

Tips for Maintaining Watch Glass

Avoid contact with hard surfaces (walls, metal tables).

Store the watch in a box when not on your wrist.

Clean gently with a microfiber cloth – not with harsh cleaning agents.

For sapphire crystal watches – beware of strong drops that could cause breakage.

For scratches on acrylic – it can be polished. For mineral or sapphire – replacement is usually required.

Frequently Asked Questions about Watch Glass Types

How do I know what type of glass my watch has?

Usually indicated in the technical specifications or on the watch's back.

Is it worth paying more for sapphire crystal?

If it's a luxury watch or for intensive daily use – absolutely yes.

What offers the best value for money?

Mineral crystal – provides a balance between cost and durability.

Can any watchmaker replace watch glass?

For acrylic – almost always. For mineral and sapphire crystal – special equipment and/or original parts are required.

Summary

Watch glass is one of the most important components affecting durability, appearance, and lifespan.

Acrylic - an inexpensive solution, but sensitive to scratches.

Mineral crystal - the most popular balance.

Sapphire crystal - the choice for luxury watches and those seeking maximum durability.

At MASTER TIME, you'll find original brand watches for women and men, such as GANT, Hugo Boss, Tommy Hilfiger, and more, with the highest quality glass. Alongside watches with sapphire glass luxurious watches like Tissot, Maserati, Gant Prestige men's collection and more. In addition, we have a professional watch laboratory that specializes in glass replacement and reliable service.