Laminated Safety Glass vs. Tempered Safety Glass: What's the Difference & Which One Do You Choose?

When selecting an industrial pressure gauge, sight glass, or other instrumentation, the window material is often overlooked. However, the type of safety glass used can significantly impact durability, operator safety, visibility, and equipment longevity.

Two of the most common safety glass options are tempered safety glass and laminated safety glass. While both are designed to improve safety over ordinary glass, they are manufactured differently and excel in different applications.

Understanding these differences can help engineers, OEMs, contractors, and maintenance professionals select the most appropriate solution for their operating environment.

What Is Tempered Safety Glass?

Tempered safety glass is standard glass that has undergone a specialized heat treatment process.

The glass is heated to approximately 620°C (1,150°F) and then rapidly cooled. This creates compressive stresses on the surface while leaving the center under tension.

The result is glass that is:

• Approximately four to five times stronger than ordinary annealed glass

• Highly resistant to impact

• Better able to withstand thermal shock

• Designed to break into small, relatively blunt fragments rather than dangerous sharp shards

  
  

This is why tempered glass is commonly found in:

• Pressure gauges

• Industrial instrumentation

• Vehicle side windows

• Machinery guards

• Building doors

• Appliance windows

  
  

Advantages of Tempered Glass

✔ Excellent impact resistance

✔ High mechanical strength

✔ Good resistance to temperature changes

✔ Clear optical properties

✔ Cost-effective

✔ Breaks into safer, rounded fragments

Limitations of Tempered Glass

Once broken, tempered glass completely disintegrates into thousands of small pieces.

While these pieces are much safer than sharp shards, the protective barrier is immediately lost.

This may expose personnel or equipment until the glass is replaced.

What Is Laminated Safety Glass?

Laminated safety glass consists of two or more layers of glass permanently bonded together with a transparent plastic interlayer, most commonly polyvinyl butyral (PVB).

During manufacturing, heat and pressure permanently fuse these materials into a single panel. If the glass breaks, the plastic interlayer holds the fragments together instead of allowing them to fall away.

This construction is commonly used in:

• Automobile windshields

• Process observation windows

• Security glazing

• Chemical plants

• Offshore facilities

• High-risk industrial environments

  
  

Advantages of Laminated Glass

✔ Retains broken glass in place

✔ Excellent personnel protection

✔ Increased security

✔ Improved sound insulation

✔ Better UV protection

✔ Continues acting as a barrier after breakage

Limitations of Laminated Glass

Compared to tempered glass, laminated glass is:

• More expensive

• Heavier

• Slightly thicker

• Less resistant to scratching (depending on construction)

• Not as resistant to repeated heavy point impacts

What Safety Glass Does Merit Use?

At Merit Instruments, operator safety is of paramount importance to us. Although tempered safety glass may be suitable for some applications, we feel that the best solution is to offer laminated safety glass in our PPX Series, PSF Series and PHDH Series pressure gauges. We also choose to use only laminated safety glass in our optional upgrades, not only for better operator safety, but to preserve the integrity of our client's process, minimizing the chances of broken glass contaminating their process.

Breaking Behavior

One of the biggest differences is how each type fails.

Feature	Tempered Safety Glass	Laminated Safety Glass
Breaks into small fragments	✔	✖
Glass remains in place	✖	✔
Continues acting as a barrier	✖	✔
Excellent impact resistance	✔	✔
High security	Moderate	Excellent

Which Is Better for Industrial Instrumentation?

The answer depends on the application.

Tempered Glass is ideal for:

• General industrial pressure gauges

• HVAC systems

• Hydronic systems

• Air compressors

• Pumps

• Hydraulic equipment

• Standard process instrumentation

  
  

Its combination of strength, optical clarity, and affordability makes it an excellent choice for many everyday industrial applications.

Laminated Glass is preferred when:

• Personnel safety is critical

• Chemical splash protection is required

• Hazardous process fluids are present

• Operators work close to instrumentation

• Additional containment is desirable

• Equipment is installed in high-risk process industries

  

Because the glass remains intact after breakage, laminated safety glass provides an additional layer of protection until maintenance can be performed.

Other Window Materials Used in Instrumentation

Depending on the application, manufacturers may also offer:

• Polycarbonate

• Acrylic

• Chemically strengthened glass

• Borosilicate glass

• Tempered borosilicate glass

Each material offers different combinations of impact resistance, chemical compatibility, scratch resistance, temperature capability, and cost.

Selecting the Right Solution

When specifying instrumentation, consider:

• Operating pressure

• Operating temperature

• Chemical exposure

• UV exposure

• Mechanical impact risk

• Operator proximity

• Industry regulations

• Required safety level

Choosing the appropriate window material can improve both equipment reliability and workplace safety.

Merit Instruments Can Help

At Merit Instruments, we understand that every industrial application has unique operating conditions. Whether you're selecting pressure gauges for general service, demanding process environments, or specialized OEM applications, choosing the right materials—including the appropriate window type—is an important part of achieving long-term performance and reliability.

Our team can help you select instrumentation solutions that match your application's pressure, temperature, environmental, and safety requirements.