Which safety or security glass does my business need?

Which safety or security glass does my business need?

Modern glass needs to be strong, safe and secure to meet the demands of today's environment. But which security glass is right for you?

Which safety of security glass does my business need?

Glass Facade

Whether it’s being used as the windscreen of a train, a wall in a skyscraper, or a high-security display cabinet, modern glass needs to have incredible strength. As manufacturing technology has progressed, so has the quality and robustness of the glass produced, giving improved flexibility in how it can be used.

For projects that require an extra level of durability, types of glass have been developed that can keep us both safe and secure. This guide aims to give you a clearer picture of the difference between safety and security glazing, as well as a comprehensive overview of the main types of each. With this information, you will be able to identify the glass solution that best meets the requirements of your project.

Overview of the types of glass

 

       

Safety glass

Toughened

Thermal toughening

Smash safely

Stairs, bath and shower screens, kitchen appliances, lab equipment.

Laminated

Laminated build

Stay in one piece

Vehicle windscreens, skylights, furniture, home windows, shop windows.

Security glass

Anti-intruder

Laminated build

Stay in one piece

Retail displays, shop fronts, customer service windows, museums, zoos.

Bullet-resistant

Laminated build

Stay in one piece

Military vehicles, cash-in-transit vehicles, embassies, banks, airports, VIP transport.

Blast-resistant

Laminated build

Stay in one piece

Embassies, airports, military vehicles, banks, and chemical and nuclear power stations

Safety glass

What is safety glass?

Safety glass is strengthened so that it will resist breaking, but, should the force applied prove to be too much, to break in a way that is safe. There are two ways that safety glass can be strengthened: through laminating or tempering.

As this glass excels at reducing the risk of injury, it is often used in locations where safety is paramount. Its extra strength allows it to be used in places where regular glass could not be, like stair or balcony balustrading, and in situations where dynamic forces and environmental conditions are at work, like airplanes and trains.
Let’s take a closer look at the two main types of safety glass.

Toughened glass

Romag glass stairs

Glass that has been thermally-strengthened to increase its toughness and allow it to crumble when broken.

Typical uses: Stairs, balustrading, structural glazing, doors, partitions, bath and shower screens, furniture, car passenger windows, trains, ships, domestic appliances, glassware, kitchen appliances, and lab equipment.

What is toughened glass?

Also known as tempered glass, toughened glass is produced with thermal treatments to increase its tensile strength — fully toughened glass can be as much as four to five times stronger than standard glass. When the glass undergoes tempering, it is heated in a furnace to incredibly high temperatures, and then immediately cooled with powerful air draughts. This causes the outer layers to be put into compression, and the inner layers to be put into tension. It is this stress that gives the glass increased solidity by pushing together any surface flaws and protecting inner layers from imperfections that can lead to cracks.

It also means that when it is exposed to enough force to break, it will crumble into small, rounded granular-like pieces that pose less threat to bystanders than traditional glass, which tends to break into sharp shards that have the potential to be deadly. This quality means that injury is less likely when a person comes into contact with a piece, and the broken glass is also a lot safer to pick up and dispose of.

Toughened glass also gains improved resistance to sudden temperature changes, allowing it to endure more rapid heating and cooling than regular glass. It is therefore not uncommon to see toughened glass being used in such places as oven doors or in lab equipment, where an extra level of heat resistance is needed.

For an extra level of safety, toughened glass can undergo heat soak testing (HST), which is a post-production process that can reduce the risk of spontaneous breakage. Incidents of breakage can often be attributed to the presence of nickel sulphide in the glass, a chemical that is left over from the manufacturing process. These particles can cause imperfections in the glass leading it to break, though the result is not always immediate, with particles sometimes lying dormant for many months before becoming an issue.

The HST process sees the toughened glass being placed in an oven once more after it has cooled, which will cause any sheets containing nickel sulphide to break when subjected to the heat. The vast majority of toughened glass has no problem with spontaneous breakage, but HST helps to eliminate those that do, making it an essential process for glass that is to be used in critical locations, such as architectural glass.

Laminated glass

Laminated glass crack example

Created through the bonding of glass layers between interlayers of polyvinyl butyral (PVB), this glass gains extra strength while being able to maintain its integrity if broken.

Typical uses: Vehicle windscreens, home windows, skylights, sun spaces, household furniture, shelving, and shop windows.

What is laminated glass?

Laminated glass is created by bonding two or more layers of glass with heat and pressure with at least one interlayer of polyvinyl butyral (PVB). The PVB acts like sticky tape when the glass breaks, allowing it to keep its integrity despite being cracked into pieces. This type, like toughened glass, offers safety from dangerous shards coming loose and causing further damage, though unlike toughened glass, it is designed to stay in one piece rather than crumbling.

The fact that laminated glass is able to maintain its shape when broken makes it the ideal choice for applications where glass needs to stay in one piece, such as the windscreen of a vehicle. Before laminated glass was used, windscreens could prove to be potentially fatal in an accident, shattering to cause injury or failing to keep the driver or passenger within the vehicle itself. Because this glass can hold together under pressure and is now industry standard, these dangers have been minimised.

An advantage of laminated glass is that it can be customised to suit a particular purpose, such as a tinted car windscreen or a home window with low-e properties. This glass can be so easily customised through the use of particular coatings or extra layers within the glass and PVB sheets.

Laminated glass also has excellent noise reduction qualities — it is able to block out more sound than standard glass. The PVB interlayer prevents sound frequencies from vibrating from one pane to the other. Even more sound can be blocked through the use of thicker glass and a wider gap between the layers. This can be particularly desirable in a busy urban environment, where the noise from industry, traffic, and passers-by can be a distraction and an annoyance.

How strong is safety glass?

Safety glass must be well made from quality materials. To measure the quality and toughness of this type of glass, there are industry standards that have to be met, and to do so, each glass product must be tested.
Both toughened and laminated safety glass has to meet a number of these standards, depending on their intended use. There are standards for the use of safety glass in architecture, transport, furniture, and more, each of which have a specific set of testing criteria to measure the product’s strength and functionality.

BS EN 12600

One important standard is BS EN 12600, which is used to test the strength of safety glass for use in buildings. The standard defines safety glass as glass which must have passed an impact test and either must not break or must break safely.

To meet this, safety glass must undergo an examination where a 50kg weight cushioned with two rubber tyres is swung at the sheet from three heights. Depending on which height the pendulum is at when the glass breaks and the type of breakage that occurs, the glass is awarded a three-character rating such as 3B2 or 3C1.


The first number represents the height class at which the pendulum was dropped from when the glass does not break or breaks safely into small fragments:

● A number 3 is awarded for a 190mm height, considered the equivalent of an adult pushing hard against the glass or a child running into it.
● A number 2 is awarded for a 450mm height, considered somewhere between an adult walking into and running into a glass door.
● A number 1 is awarded for a 1200mm height, considered a critical application, such as someone falling onto the surface.

The second letter represents the type of breakage mode:

● Type A represents a breakage with large, sharp fragments.
● Type B represents a breakage where the fragments are held together.
● Type C represents a breakage with small, harmless pieces.

The third letter is awarded for the height class at which the glass does not break or allow penetration.

BS EN 12150

Although toughened glass for architecture has to meet the requirements for BS EN 12600 for use in buildings, it also has to meet its own standard of BS EN 12150, which covers the tolerance, flatness, edge-work, fragmentation, and physical and mechanical properties of thermally toughened safety glass. It should be noted that this standard does not apply to laminated safety glass.

Security glass

What is security glass?

Security glass shares many of the same qualities as safety glass. It is extra strong and will resist force more effectively than standard products, and it also shares the non-shatter safety features of laminated glass. Where security glass differs is in the specialised level of protection that it provides. It is tailor-made to combat certain threats, such as physical attacks, bullets, and blasts, with a design and materials that are chosen specifically to stand up to them.

The manufacturing of this type of product is not dissimilar to that of laminated glass, making use of layers to build strength and to maintain integrity. Security glass uses multiple panes of various thickness to deliver a product that will stand up to more extreme threats. As you move up through the levels of defence required, security glass can be built using thicker, stronger glass and with more layers to stand up to the anticipated impact.

This type of glass sees most use when something vulnerable needs defending or when a high-value item or high-ranking person needs to be safeguarded. Therefore, it likely that you will see security glass in locations like embassies, banks, jewellers, and petrol stations, or in vehicles like military trucks, executive cars, and cash-in-transit vans.

Anti-intruder glass

Security Glass

© Frank Vincentz - licence

This glass is designed to successfully protect someone from the sustained physical attack of an aggressor armed with a non-ballistic weapon, such as a hammer or an axe.

Typical uses: High value retail displays, shop fronts, customer service windows, government buildings, museums, zoos.

How strong is anti-intruder glass?

By definition, anti-intruder glass has to be strong enough to prevent a person from smashing their way through. To help businesses decide on the level of protection they require, there are industry standards that act as a benchmark for measuring the strength of the glass.

For anti-intruder glass, the relevant industry standards are the European standard BS EN 356, for testing and classification of resistance against manual attack, and LPS 1270, set by the UK-based Loss Prevention Certification Board (LPCB).

BS EN 356

The European standard BS EN 356 offers eight levels of classification. In this process, glass is subjected to a number of tests to gauge its strength. The glass is awarded a level depending on what it is able to withstand. The first five levels comprise a ball drop test, where a steel ball weighing 4.11kg is dropped onto the glass multiple times from several increasing heights. To pass the test, the ball must not penetrate the glass. Below are the specifications of these test levels.

The last three levels of the BS EN 356 test involve more sustained assaults with weapons against the glass, in this case hammer and axe blows. The test involves a hydraulically driven hammer head that measures 40mm and weighs 2kg being used to attack the glass a minimum of 12 times, before a 2kg axe head is used another 12 times. The intention is to cut a hole of 400mm in the glass, and the product is classified by the number of blows it takes to reach this point. Below are the specifications of these test levels.

LPS 1270

This standard was created to further test anti-intruder glass beyond the levels of BS EN 356. It is designed to replicate a greater range of tools and the different risks that intruders pose to the glass. The tests are carried out by a person, rather than being automated like the European standards.

Eight grades of classification are offered, with variation in the tools and periods of time they are used in each round of testing. The sheets of glass used in the test are 865mm wide by 1930mm high, and must have been kept at a temperature between 18°C and 30°C prior to the examination.

Glass products are tested for three categories of hole appearing in the sheet. The hole sizes are:
● 1st digit in the rating: Local penetration. This hole is 8mm by 25mm, and represents a gap in which an intruder could use a tool to operate a handle or access bar on the other side of the glass.
● 2nd digit in the rating: Hand hole. This hole is 60mm in diameter and represents a gap in which an intruder could use their hand to access valuables or a locking mechanism.
● 3rd digit in the rating: Complete access. This hole is 400mm by 225mm and represents a gap which provides complete access for the intruder.

Depending on their performance — how large the hole is and how quickly it was made — they are assigned a three-digit rating at the end of the examination, e.g. 2-6-4 or 1-5-4. Each digit in the rating corresponds to one of the three categories of hole and which number it receives depends on how the product performed when tested.

During the exam, the tester has eight pre-selected tool sets available to him, and a set number of minutes in which to attack the glass. Depending on the severity of the toolset and length of time it takes to achieve the desired hole size, the glass will earn its numbered rating, as set out below.

Bullet-resistant glass

A type of glass designed to stop bullets from piercing the surface and causing injury to the intended target.

Typical uses: Military vehicles, cash-in-transit vehicles, embassies, banks, airports, VIP transport.

What is bullet-resistant glass?

Bullet-resistant glass has the objective of stopping bullets discharged from a range of different firearms at a variety of distances. This type usually consists of several layers of glass and a type of thermoplastic, which are bonded together to create a single sheet that can be inches thick.

The glass used in bullet-resistant products is often toughened to give extra resistance, and to create the safer crumbling effect associated with glass that has undergone thermal strengthening. The thermoplastic layers found between the sheets can vary in type, but two widely used materials are polyvinyl butryal (PVB) and polycarbonate. While PVB is an industry favourite and has been used for a number of years, polycarbonate is often preferred in higher spec products due to its extra toughness and lighter weight.

The plastic and glass layers are arranged in a way that is designed to stop the bullet piercing the innermost layer of the sheet. The glass layers are tougher than the plastic, and it is their job to take the brunt of the force when the projectile makes contact, flattening the bullet as it moves through. The more malleable plastic is there to absorb and disperse the force of the impact, spreading the bullet’s energy across the whole of the sheet and slowing it to a stop. At the same time, the laminated build of the glass ensures that it remains in one piece without shattering.

A less desirable property of bullet-resistant glass is its tendency to produce spall, tiny pieces of glass that are ejected from the innermost layer when the bullet impacts. These fragments can be dangerous to people nearby, especially if they are close to the glass. To reduce or eliminate this effect, manufacturers use polycarbonate or polyester rear layers designed to remain intact under impact. This is commonly used in high-performance or premium bullet-resistant glass, often referred to as ‘low spall glass’.

How strong is bullet-resistant glass?

To stop a bullet travelling at incredible speeds, it goes without saying that bullet-resistant glass needs to be tough. However, the glass also needs an expert level of engineering in the manufacturing process to ensure that it doesn’t fail should it ever be needed.

As the quality of this type of glass can be the only difference between safety and harm, there are industry standards that every product on the market has to go through to ensure it is up to the task of stopping a bullet. The standard used to test and classify bullet-resistant glass is BS EN 1063, which is set by the European Committee of Standardisation.

The BS EN 1063 standard has seven classes for small arms fire (BR1 to BR7), and two for shotguns (SG1 and SG2). To earn a certain classification, the sheet of glass must be able to stop the specified number of shots when they are fired within 120mm of one another from a pre-determined range. The product must be able to do this without shattering. As the glass progresses through the threat levels, the type of firearm and ammunition becomes more powerful, meaning that the strongest glass must be able to stop bullets from the more powerful weapons at the highest levels of testing.

You can see the requirements for each of the nine levels in the table below.

LB - Lead Bullet
FJ - Full Metal Jacket
FN - Flat Nose
RN - Round Nose
CB - Cone Bullet
PB - Pointed Bullet
SC - Soft Core (lead)
SCP - Soft Core (lead) & Steel Penetrator
HC - Hard core, steel hardness > 63 HRC

There is also an additional rating attached to the glass during the test that measures the amount of spall produced. An object called a witness plate — a thin layer of foil that any glass particles will pass through should they be ejected — is placed behind the sheet throughout each test. If no spall is produced and the innermost layer of the sheet is not pierced, the product is awarded a no-splinter rating (NS), while glass that does produce spall receives a splinter (S) rating.

Blast-resistant glass

Glass designed to resist the pressure force of a nearby blast without shattering and producing shards of glass that could pose a deadly risk.

Typical uses: Embassies, consulates, airports, railway stations, military vehicles and buildings, banks, VIP transport, oil and gas testing facilities, and chemical and nuclear power stations.

What is blast-resistant glass?

In the tragic event of a blast occurring, one of the biggest causes of injury and loss of life is from flying shards of glass that are set loose by the force of the explosion. With the increase in bomb attacks in recent decades, it has become apparent that windows are one of the key areas that need to be secured in order to protect those that may be standing nearby. The intense power of many blasts mean that standard monolithic glass, and even toughened glass, are simply not able to cope. This has created the need for blast-resistant windows that can absorb the impact and also remain in one piece.

Heavily laminated glass is the most effective design for meeting this requirement, as not only will the thermoplastic layers absorb much of the blast pressure, but the layered build means that it will not shatter into pieces. Additionally, the strength and flexibility of laminated glass can resist the impact of projectiles, such as rocks, shrapnel, or other debris, which can be scattered in an explosion. Combining this glass product with a blast-resistant window frame goes a long way to providing enhanced security for vulnerable buildings.

Standard blast-resistant glass is usually made with PVB interlayers, which has great shock absorption qualities, though materials like polycarbonate can also be used for increased strength. The risk of spall in a blast can also be greatly reduced by applying a polyester-based film to the rear surface of the glass, which will act as a barrier against any loose glass particles.

How strong is blast-resistant glass?

As can be expected, blast-resistant glass needs to be very strong to resist the incredible forces that can be created in an explosion. It must also be reliable in order to protect the lives of the people who may be standing nearby.

Before a blast-resistant glass can be chosen and installed, an evaluation needs to take place to determine what level of protection is required for the situation. This will take into account such factors as the likely proximity of the blast and how strong it could potentially be.

In order to identify which type of glass is appropriate, there is a European standard which all blast-resistant glass must be tested and classified under. The ratings awarded under this standard make it much easier to make an accurate decision as to whether it is suitable for a particular project or situation. This standard is known as EN BS 13541, and covers the testing and classification of resistance against explosion pressure of glass in buildings.

For the examination for this standard, a shock tube — an instrument used to replicate and direct blast waves — is used to test the strength of the product under explosive pressure. This device is used to direct blast waves at a sheet of glass measuring 1100mm by 900mm. The classification of the glass’s explosion pressure resistance is calculated by testing three samples with increasing pressure levels, with positive pressure phase duration remaining the same for each test. The three levels of categorisation are summarised in the table below.

To succeed at each level of testing, each glass sample must not have any ‘through holes’ from the front to the back of the glass, and no gap opened between the edge of the sheet and the clamping mechanism. The glass will be rewarded with the highest classification it can withstand, as well as secondary no-splinter or splinter designation, depending on whether any spall was ejected from the inner layer after each test.

Safety and security glass at Romag

At Romag, we specialise in designing and manufacturing safety and security glass to meet the needs of our diverse customer base. Take a look at our projects page to see how we have met the needs of a few of our clients.

Whether you need toughened or laminated glass for your project, our experienced team can help you create a solution that will offer complete safety. If you’re looking for anti-intruder, bullet-resistant, or blast-resistant glazing to add an extra level of security to your project, our team can also help.

Get in touch with one of our safety glass experts today if you have any questions about any of the safety or security glass products discussed in this guide.