Double Glazing guide to glass types

Many Peterborough homeowner not forgetting general builders do not know or understand the difference between the various glazing options. So throughout this double glazing blog we will discuss the four main types of glazing options and their purpose for installation.

Flat glass was originally produced via a Float Process. The Float Process was invented by Sir Alastair Pilkington in 1952. This process allowed larger and better consistency within the glass panels to be manufactured than ever before. In 2021 there are more than 260 float plants worldwide which are producing glass which is wide as 3 meters and as thick as 25mm. Some of these plants are an astonishing 1 km long, which can operate to produce 800,000 tonnes of glass per week! Pilkington glass is the most widely known type of glass in the UK market today. All double glazing manufacturers use Pilkington obscured glass designs within their windows and doors.

When we talk about the actually strength of the various glass types, this is dependent on the rate that the glass is cooled. As mentioned earlier, there are four main types or strengths of glass.

Depending on how glass is made can change its ability to reflect or even refract natural light. Which is extremely important while trying to maintain room temperature. Glass can quite easily be manufactured to be shaped or curved in a particular way to meet the requirements of the architectural requirements.

1) Annealed Glass

The anneal glass is the most popular choice when it comes to double glazing. Anneal is extremely clear and smooth which is often used to enhance vision. Anneal can transmit 87% of light through it, making it the most popular choice when it comes to glazing a Peterborough property.

Anneal glass otherwise known as float glass is allowed to cool down naturally to room temperature after the heating process. This allows the glass to natural cool down without correcting internal stresses. Once this glass is cooled it can then be cut and used for double glazing windows.

Anneal can then be manipulated into further processes to obtain tempered glass, laminated glass or toughened glass. To create tinted glass a coat of metal oxide can be applied, this offers protection from solar glare which can often be found in conservatory roofs or office buildings.

Frosted anneal glass is produced when typical anneal glass is sandblasted or even acid etched which creates a rough misty surface in appearance. This process can be used to manipulate different obscurity levels of obscured glass designs. These obscured glass selections are often seen within composite door glazing, side panels or even toilet windows.

2) Heat Strengthened Glass

Heat Strengthen glass is produced when anneal glass is reheated to around 650 to 700deg C. This glass is then cooled back down to room temperature very quickly. When anneal glass is reheated strength of the glass is increased as well as its thermal efficiency. If this glass in broken, this will produce similar size brakes as anneal glass, however it will be held together which is much safer than anneal.

Heated strength glass has its limitations due to its overall strength compared to toughened or laminated glass. So its purpose would be of similar nature to anneal glass however with a slightly stronger necessity and the requirement not to splinter into thousands of little pieces.

3) Tempered or Toughened Glass

Tempered otherwise known as toughened glass is often located in structures that require a robust window solution. The process is similar to heated strengthened as anneal is heated to around 700 degrees C but via conduction, convection and radiation. This glass is then cooled by blasting cool air on both surfaces of the glass. As the inside of the glass will now be at a different temperature of the outside surfaces, this changes the physical properties. These stresses are of a compressive nature causes the glass to become between 4 and 5 times stronger than anneal glass.

Induced stresses to the surface of the toughened glass enhances its ability to break. If it does break then it produces many small particles which are far safer than long pointy pieces which could easily lead to serious injury.

4) Laminated Glass

All types of glass listed within this double glazing blog can be lamented. Laminated glass offers many advantages over its rivals. Firstly safety and then security! If this glass is broken then it will be held together by the inner laminated layer. This also reduces the chances of glass being thrown into fragments or reducing the risk of glass penetration.

If for example a glass side panel is shatters, it is highly unlikely that the second or rear glass panel would also break at this time. As the inner laminated layer would hold the broken glass together whilst protecting the rear panel. Not forgetting that laminated toughened glass will be over 5 times stronger than standard glazing.

Structural interlayers can also be incorporated into this glazing to maximise strength when high loads are required. Sound dampening or fire resistant properties can also be manufactured within the interlayers if needed.


You are now aware that there are mainly 4 types of glazing options. All of these options originated from appeal glass and then manipulated via how this glazing is heated, cooled and at what rate. To enhance over strength, soundproofing and security then laminated or other interlayer properties can be applied during its manufacturing process.

Thank you for reading this blog and if you have any additional questions please don’t hesitate in contacting Peterborough Doors!