Both tempered glass and borosilicate glass have their advantages and disadvantages depending on the application. In this article, we will compare the key properties, uses, costs, and overall pros and cons of each type of glass to help you determine which is better for your needs.
What is Tempered Glass?
Tempered glass, also known as toughened glass, is a type of safety glass that has been treated with a heating and rapid cooling process to increase its strength. This tempering process creates balanced internal stresses in the glass that cause it to shatter into small, relatively harmless pieces when broken instead of large, sharp shards.
The key properties of tempered glass include:
- Around 4-5 times stronger than regular annealed glass
- More resistant to impacts and temperature changes
- When broken, shatters into small granular pieces rather than sharp shards
- Can withstand higher wind loads and human impact forces
Tempered glass is commonly used for:
- Side and rear windows in vehicles
- Architectural glass doors and wall partitions
- Appliance screens and covers
- Smartphone and device screens
- Safety glass in hazardous environments
What is Borosilicate Glass?
Borosilicate glass, also known as Pyrex, is a type of glass made by adding boron oxide to silica glass. This results in a glass with low thermal expansion, high thermal shock resistance, and high chemical durability.
The key properties of borosilicate glass include:
- Very low thermal expansion coefficient
- Excellent resistance to thermal shock
- High chemical durability and corrosion resistance
- Withstands high temperatures up to 500°C
- Transparent to UV light
Borosilicate glass is widely used for:
- Laboratory glassware like beakers, flasks, and test tubes
- Cookware like baking dishes and stove-top pans
- Pharmaceutical packaging
- Sealants for electrical insulators
- Optics like prisms and lens elements
Strength and Durability
In terms of mechanical strength and durability, tempered glass is generally superior to borosilicate glass. The tempering process makes tempered glass around 4-5 times stronger than regular annealed glass. This allows it to withstand significantly higher loads and impacts without breaking.
Borosilicate glass is not tempered and has similar mechanical strength to regular annealed glass. It also tends to fracture into long splinters rather than small granular chunks when broken. This makes tempered glass the safer choice for applications like automotive and architectural glass.
However, borosilicate glass has excellent thermal shock resistance and durability against chemicals, corrosion, and weathering. It can withstand rapid temperature changes up to 180°C without cracking or shattering. So for applications involving heat, caustic chemicals, or outdoor exposure, borosilicate glass will likely outperform tempered glass.
Optical Properties
Both tempered and borosilicate glass can be produced to have very high optical quality and light transmission. But tempered glass does suffer some slight optical distortion from the tempering process. The rapid heating and cooling involved can introduce minor variations and stresses that affect optical properties.
Borosilicate glass is often the preferred choice for precision optics like lenses, prisms, and cell phone camera elements where optical clarity is critical. It also transmits UV light better than standard tempered glass.
Cost Comparison
From a cost perspective, basic clear borosilicate glass is generally cheaper than tempered glass. The additional processing steps required to temper glass raises its manufacturing cost. Here is a rough comparison of cost per square foot:
| Glass Type | Cost per Square Foot |
| Clear Borosilicate Glass | $1 – $5 |
| Clear Tempered Glass | $2 – $15 |
However, more advanced borosilicate glass formulations with high UV transmission or precision optical qualities can be more expensive than tempered glass. Coatings and laminations will also add cost to tempered glass.
Applications and Uses
The different properties of tempered and borosilicate glass make them suitable for different applications:
Tempered Glass Applications
- Side and rear windows in vehicles – safety and durability
- Architectural facades and partitions – strength and safety
- Appliance screens and covers – impact resistance
- Smartphone display screens – strength and scratch resistance
- Sports arena glass railings and panels – safety
Borosilicate Glass Applications
- Laboratory ware like beakers – thermal shock resistance
- Cookware like Pyrex – high heat tolerance
- Pharma packaging vials – chemical durability
- Sealants for electrical insulators – high dielectric strength
- Optical components – high optical transmission
Pros and Cons of Tempered Glass
Pros:
- Around 4-5 times stronger than annealed glass
- Safer due to shattering into small granular pieces
- Withstands high wind, human impact, and temperature fluctuations
- Suitable for applications requiring safety or strength
Cons:
- More expensive than annealed or borosilicate glass
- Slight optical distortion from tempering process
- Not suitable for high heat applications above 300°C
- Prone to spontaneous shattering due to nickel sulfide inclusions
Pros and Cons of Borosilicate Glass
Pros:
- Excellent thermal shock resistance
- Can withstand rapid and extreme temperature changes
- High strength and durability against chemicals and corrosion
- Low thermal expansion provides dimensional stability
- No optical distortion like tempered glass
Cons:
- Lower mechanical strength than tempered glass
- Fractures into long sharp shards rather than small chunks
- More expensive than soda-lime glass
- Requires careful handling to prevent cracking or breaking
Conclusion
In summary, tempered glass is the best choice when safety, strength, and impact resistance are critical requirements. It is suitable for applications like windows, doors, displays, and partitions where its high mechanical strength provides safety from breakage and human impact.
For applications where thermal durability, chemical resistance, and optical clarity are priorities, borosilicate glass is generally the better option. Its ability to withstand rapid temperature changes, corrosion, and UV light transmission make it ideal for cookware, labware, pharmaceuticals, and optics.
The ideal glass type depends on the specific application and requirements. In many cases, borosilicate glass may be used for components that require its strengths while a tempered glass enclosure provides the necessary safety shielding around it. Working with a glass manufacturer to understand your particular needs is recommended to select the optimal glass solution.