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How is Sapphire Glass Made?

Custom sapphire glass

It’s not unbeknownst to glassmakers and expert engineers how sapphire glass is made. A short answer would be through the process known as the Verneuil method, where aluminum oxide (corundum) is melted and slowly crystallized into a cylindrical boule. This boule is then sliced into thin sheets, which are precisely polished to achieve the desired optical clarity.

The long one involves sourcing of materials and components, multiple preparatory guidelines, and processing of the materials needed to the mechanical and functional aspect of it.

In this guide, we’ll discuss the avenue of how sapphire glass is made and produced. You will learn everything you have to know about the production and manufacturing of sapphire glass – from its sourcing, the shaping, the molding, and even the processing and polishing, we got it all for you!

Is Sapphire Glass Made From Real Sapphire?


Figure 1: An Example of What Sapphire Crystal Looks Like

No, sapphire glass is made from synthetic sapphire, which is not really a type of glass, but a hexagonal crystalline that is formed from aluminum oxide material. It is an extremely durable, hard, and tough material that has high levels of resistance to heat and temperature.

So, in conclusion, it’s technically not real sapphire, but it’s close to the sapphire you know with varying hues and colors and the difference lies on the color and transparency.

General Name

Here’s a quick fun fact! Sapphire is the commonly and generally-labeled name for all corundum gems except for Red Ruby. Therefore, when you identify sapphire, you’re not always identifying the gemstone, instead, sapphire glass or crystal.

Sapphire Glass vs. Sapphire Crystal


Figure 2: Different shapes and forms of sapphire crystals for different purposes

Sapphire glass and sapphire crystal are commonly misinterpreted as two separate objects and materials, when, in reality, it’s just the same. Only the terminology is different because sapphire glass is used in the industrial sense, while sapphire crystal is what’s commonly used in the watches, jewelry, and wearables industry.

Made in extremely high temperatures, these sapphire glass and crystal units are used in a wide array of businesses, industries, and sectors.

Where is Sapphire Glass Used?


Figure 3: The Different Applications of Sapphire Glass

Following the comparison between sapphire crystal and glass, where do you often use the latter? Sapphire glass is used in a lot of different fields and industries. As a matter of fact, they’re mostly found in fields that require specific glass and material types that fit its description.

You’ll mostly find sapphire glass in the following industries and applications:

  • Watch and Jewelry Industry
  • Interior and Home Design and Architecture
  • Advanced and Modern Engineering
  • Electronics and Technology
  • Optics Industry
  • Aerospace and Aeronautics Sector
  • Automotive and Car Parts
  • And Many More!

Sapphire glass is a versatile and flexible material that may be used in various applications and situations!

How Strong is Sapphire Glass?


Figure 4: Sapphire Glass is Extremely Strong, Durable, Resilient, and Long-Lasting

Sapphire glass is labeled and known as one of the best and strongest synthetic materials out there. It is abrasion and scratch resistant, and it has a hardness rating of 9 in the Mohs scale, too. You wouldn’t be disappointed with the resilience and strength that it has because it’s going to exceed your expectations.

It has a hardness rating of 2,000 HV, which is substantially high. This means that sapphire crystals can only be scratched and damaged by materials harder than it–like real diamonds that are rated 4,500 to 10,000 only.

On a comparative scale, sapphire glass is a lot tougher, more durable, and longer-lasting than other kinds and types of glass, if we are to look at it in impact and pressure scale, making it an ideal material and component for a specific set of wearables and devices.

Here’s a quick video from Ben’s Watch Club testing the strength and toughness of sapphire glass.

Is Sapphire Glass Expensive?

Yes, it is. In fact, out of all the modern and current options, sapphire crystal is the most expensive of the watch glasses in the industry. Sapphire glass is relatively expensive compared to other common glass materials. Its production process, which involves the growth and precision polishing of synthetic sapphire, contributes to the higher cost.

The durability and scratch resistance sapphire crystals offer make it a valuable choice for premium electronic devices and luxury watches, perfectly justifying the added expense to it. While the costs vary, the exact price can vary depending on the size and application.

Generally, though, its price range falls on the higher end of the price spectrum for transparent materials.

NOTE: These rates and prices, on average, are at the median range. However, you’ll also be able to find cheaper and more expensive ones in this list.

How Much is Sapphire Glass?

So, that begs the question – how much is sapphire glass, really? By looking at the market’s trend, we see that the average price of sapphire glass is at $1 to $10 per piece. The price scales from $1 depending on the structure, thickness, and the process done to create it.

The shape doesn’t necessarily have any impact on the price, but, it’s safe to say that the more accurate the unit is, the more expensive it gets.

Check out the average rate and price of sapphire glass in AliExpress and Made-In-China!

Is Sapphire Glass Natural?


Figure 5: Three Round Sapphire Glasses

No, it’s not. The sapphire glass or sapphire crystal talked about in this sense refers to synthetic sapphire. It’s an entirely different and separate material from the blue sapphire we know, and it is commonly misunderstood by a lot of people.

So, to finalize this, sapphire glass – which is the typical material used for watch glasses, mirrors, and other stuff that requires an alternative of glass, is not natural. Sapphire (gemstone), on the other hand, is the natural corundum, which is, in no way, not used to create sapphire crystal.

Types of Watch Glass: Acrylic vs. Mineral vs. Sapphire Glass


Figure 6: Comparison Of Acrylic, Mineral, And Sapphire Glass Units

There’ll never be a shortage of glass types when it comes to watches, but there are three that are considered most common and used: acrylic, mineral, and sapphire glass. Let’s take a look at these three and try to compare them with one another!

Acrylic Glass

Acrylic watch crystals are lightweight and inexpensive. They are also known as plastic or hesalite crystals. Their features include great impact resistance and ease of replacement. These crystals are common in antique and entry-level timepieces. They are, however, prone to scratching and require constant cleaning.

Pros of Acrylic Glass or Hesalite Glass

  • Impact-resistant.
  • Lightweight.
  • Inexpensive.
  • Easy to replace.

Cons of Acrylic Glass or Hesalite Glass

  • Prone to scratches.
  • Requires frequent polishing.
  • Lower optical clarity.

Mineral Glass

Mineral glass crystals are formed of tempered glass and have a higher scratch resistance than acrylic. They have good impact resistance and are used in mid-range timepieces. These crystals are inexpensive, but they can chip with time. Mineral glass strikes a balance between durability and cost-effectiveness.

Pros of Mineral Glass

  • More scratch-resistant than acrylic.
  • Decent impact resistance.
  • Affordable.
  • Better optical clarity compared to acrylic.

Cons of Mineral Glass

  • Can still scratch over time.
  • Not as scratch-resistant as sapphire glass.

Sapphire Glass

Last but most definitely not least are sapphire glass. Sapphire watch crystals, made from synthetic sapphire, are the most premium option. They are incredibly hard and virtually scratch-proof, providing unparalleled clarity.

Furthermore, they are commonly found in high-end and luxury watches. While more expensive, its exceptional durability and scratch resistance make it a long-lasting investment. It offers the best protection for your watch and maintains its pristine appearance for years.

Pros of Sapphire Glass

  • Exceptionally hard and scratch-proof.
  • Unparalleled optical clarity.
  • Long-lasting and durable.
  • Maintains a pristine appearance over time.

Cons of Sapphire Glass

  • Most expensive option.
  • More brittle and less impact-resistant than other types.
  • Replacement can be costly.

These differences always have to be extremely precise, because they are, after all, different. There are other glassmaking experts and glass manufacturers that have their own views and opinions about it. Here’s what Ben’s Watch Club has to say about the differences of these watch glass types!

The Heart of the Process: How is Sapphire Glass Made and Manufactured?


Figure 7: What a Sapphire Glass Boule Looks Like: Part of the Process of How It’s Made

The process of manufacturing or producing sapphire glass isn’t limited in a singularity. In fact, many manufacturers boast and take pride in how they do it because of certain steps and features that contribute to the overall quality of the product.

What we have here is the general and common way of how to do it:

Step 1: Preparing the Sapphire Seed and Crucible

The journey to manufacturing sapphire glass starts in specialized furnaces. Within these furnaces, extreme heat and pressure work their magic on aluminum oxide to create sapphire crystal. Here’s how it begins:

Sapphire Seed Placement

The process kicks off with the placement of a “sapphire seed,” a disk-shaped object about the size of a hockey puck. This seed serves as the foundation for the sapphire crystal’s growth.

Then, the sapphire seed is mixed with aluminum oxide and uncrystallized sapphire material known as “crackle.” This combination is a critical part of the process.

Step 2: The Crucible and Crystallization

The following stage of sapphire crystal production takes place within the crucible and furnace, where heat and accuracy are critical.

Crucible Placement

The sapphire seed, aluminum oxide, and crackling coexist in the crucible, which is a metal container. It is essential for the creation of the crystal.

Extreme Heat

The furnace is heated to approximately 4,000 degrees Fahrenheit, producing an atmosphere in which the components merge together. This intense heat is an important catalyst in the process.

Cooling Cycles

After the fusion, the molten material is subjected to a series of cooling cycles spanning about two weeks. These cycles are necessary for the sapphire to crystallize into its desired form.

The outcome of this phase is a cylindrical piece of sapphire referred to as a “sapphire boule.” It’s a large, raw form of sapphire that can be further processed for various applications, such as LEDs and aircraft windows.

Step 3: Crafting Sapphire Wafers

To create smartphone screens, sapphire wafers are derived from the sapphire boules:

Extracting Smaller Cubes

From the sapphire boule, a smaller cube is extracted, and it is this cube that becomes the source of sapphire wafers.

Sapphire Wafer Production

These sapphire wafers are the foundation for crafting smartphone displays. They can be drilled and cut to create paper-thin sheets of sapphire for this specific application.

Step 4: Sapphire Screen Manufacturing

The manufacturing process for sapphire screens involves advanced techniques to ensure their durability and optical clarity:

High-Energy Proton Bombardment

In this phase, the sapphire wafer undergoes a process called “proton-induced exfoliation” (PIE). High-energy protons (hydrogen ions) are directed at the wafer, penetrating beneath its surface.

Formation of Microbubbles: The high-velocity hydrogen ions generate a line of hydrogen gas microbubbles beneath the surface of the sapphire wafer.

Heating Process: The wafer is subjected to high heat, which causes the formation of super-thin sapphire sheets by separating them from the original wafer. This process is repeated multiple times until the entire wafer is utilized, resulting in numerous ultra-thin sheets.

End Product: The end product of this intricate process is the coveted sapphire screen, known for its exceptional strength, optical clarity, and scratch resistance, making it a sought-after component in advanced technology applications, including smartphone displays.

That’s about it! That is the generic, yet comprehensive way of manufacturing and making sapphire glass!

Check out this video of how sapphire crystal units are made and manufactured!

What Can Break Sapphire Glass?

Sapphire glass, renowned for its durability, can still break. Besides its weakness when put up against real diamonds, sapphire glass crystals can still break if met with any of the following conditions:

  • Extreme Force: A substantial impact or force, such as dropping a heavy object on it, can shatter sapphire glass.
  • Abrasion: While highly scratch-resistant, materials even harder than sapphire, like diamonds, can scratch or damage it.
  • Flaws: Existing structural flaws or inclusions within the glass can weaken it and make it more prone to breakage.
  • Edge Stress: Sharp impacts concentrated on the edges can cause cracks or chips.
  • Thermal Shock: Rapid temperature changes, particularly extreme heat followed by rapid cooling, may induce thermal stress and lead to cracks.
  • Manufacturing Defects: Rare defects in the manufacturing process might leave weak points, making the glass more susceptible to breakage.

With this information, we can safely conclude that sapphire glass is robust, but not immune to specific factors. Just because it’s one of the sturdiest and most durable materials on the face of the planet, doesn’t mean it’s indestructible.

What are the Benefits of Sapphire Crystal?

Many would say that the benefits of sapphire crystal come quite obvious. However, it’s still worth mentioning, after knowing and understanding the fact that it’s advantageous and beneficial:

Exceptional Hardness

Sapphire crystal is one of the hardest materials, offering superior scratch resistance, ensuring a pristine appearance. Its hardness level can easily be put side-by-side with real diamonds, as well as its durability and resilience.

Optical Clarity

Unrivaled transparency and minimal light distortion result in clear, sharp displays and camera lenses.

Durability

Sapphire glass can easily withstand wear and tear, making it ideal for high-impact applications in watches, smartphones, and aerospace. It’s also a great material for temperature-sensitive applications and industries, too.

Excellent Chemical Resistance

Other than its mechanical and physical strengths, sapphire glass is also known to resist corrosion, especially from harsh chemicals, maintaining its integrity.

Longevity

Lastly, it’s longevity. Thanks to its strength, resistances, and robustness, it ensures a longer lifespan for devices and components.

What Smartwatches Use Sapphire Glass?


Figure 8: An Image of a Smartwatch that Uses Sapphire Glass as its Base

While most technologies and gadgets today are dominated by Gorilla Glass, there are a few that still use sapphire glass for the coating and covers of their smartwatches and gadgets.

Some of the most common are within the range of Apple Watch 2 and Apple Watch 7. The low-end aluminum models use Ion-X glass, not sapphire glass. Besides Apple Watches, the Huawei GT 2 Pro, Withings ScanWatch, and Fenix 6 and 7 Sapphire Editions also use sapphire glass.

Get World-Class Quality Sapphire Glass From GLASHern and Get Excellent Pre and After-Sales Services

GLASHern has been one of China’s top sapphire glass manufacturers, directed for advanced and heavy-volume use. We offer multiple range of services and glass products from cutting, drilling to printing, strengthening, and others!

Besides our services, we’re also adept in the fabrication of glass products like Gorilla Glass, Quartz Glass, Architectural Glass, Laminated Glass, to UV-Blocking Glass, Ultra-Thin Glass, and many more!

GLASHern has a dependable team of glassmaking experts and engineers who are always ready to help you with what you need.

  • We have a Research & Development Team (R&D) ready to help you with the sapphire glass you need
  • We have over 200 products in 10+ business categories
  • Our processes have been mapped and planned out perfectly
  • We can create blueprints of your project and give you free samples
  • Our lead time is within 3 weeks!

Get a free quotation and never worry about where you can get superior-quality sapphire glass ever again!

You’ll never look for another sapphire glass manufacturer after you experience the GLASHern way!

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