Types of Glass

There are numerous types of glass which are made for different purposes. Here outlines these types of glass. Remember: most manufactured glass undergoes more than one process to increase its durability overall.

Annealed Glass

Annealing is a method of relieving residual internal stresses in glass that are introduced during its manufacturing process (such as glass cutting) by heating it to its stress-relief point (annealing point). At this viscosity, the glass is still too hard for significant external deformation without it breaking, yet it is malleable enough to relax internal stresses by microscopic flow. The glass will heat-soak until its temperature is even throughout and the stress relief is adequate.

Afterwards, the glass will cool at a predetermined rate until its temperature drops below the strain point (typically in a kiln). The product is finally cooled to room temperature at a rate limited by the heat capacity, thickness, thermal conductivity and thermal expansion coefficient of the glass. The material can now be cut, drilled or polished without risk of it shattering. This type of glass is crucial in the manufacturing of almost all modern glass.

Chemically Strengthened Glass

This type of glass is made more durable by a post-production chemical process. This is done by a surface finishing process, where glass is submerged in a body of potassium nitrates at 300°C. This causes an ionic exchange reaction where smaller sodium ions on the glass surface are replaced by larger potassium ions from the potassium solution, where the same amount of potassium ions compared to sodium ions take up the surface area of the glass.

Resultantly, the larger potassium ions cause the surface of the glass to enter a state of compression, whilst the insides of the glass generate a force of compensating tension. This essentially means the same tension is acting on every side of the glass, and so a much greater force would be needed to break the glass when internal forces are acting against it.

Enamelled Glass

Also known as painted glass, this type of glass has been decorated with enamel (powdered glass, usually mixed with a binder) and then fired to fuse it, creating translucent or opaque glass. It allows painting using several colours, and along with glass engraving, has historically been the main technique used to create any desired image on glass.

In this context, ‘enamel’ refers to glass made into a flexible form; set on an object in another material and then melted to fuse them with the object. Glass is enamelled by mixing powdered glass, either already coloured, or clear glass mixed with the pigments, with a binder such as acacia gum which gives a thick liquid texture allowing it to be painted with brushes. Generally, the desired colours only appear when the piece is fired, adding to the artist’s difficulties.

Float Glass

Using this technique in the manufacturing process of modern windows, float glass is a sheet of glass produced by pouring molten glass on a bed of metal, such as steel. The glass is then rolled out, which creates glass that contains a uniform level of thickness, and very flat surfaces – especially when a double roller table is employed as opposed to a single roller.

Furthermore, float glass is a type of glass which is a subcategory of rolled glass.

Insulated Glass

Often termed double, or triple-glazing, this type of glass is where two or three panes of glass are lined next to each other in, for example, a window, where small spaces in-between them are occupied by argon. This creates an insulating barrier which prevents heat passing through both sides of the window.

All Trendguard’s glass we supply in our windows and doors are rated A+ in their energy efficiency. For all our windows, we guarantee your glass will be airtight insulated.

Low-emissivity Glass

Low-emissivity (Low-E, or sometimes referred to as solar control) glass is a type of energy efficient glass designed to prevent heat passing through it, which is done through passive and solar control coatings. These coatings function on the principle of the electromagnetic (EM) spectrum. This is the range of all types of EM radiation, including ultraviolet (UV) and infra-red (IR) radiation which influences thermal energy transfer the most.

Low-E coatings have been developed to minimise the amount of ultraviolet and infrared light that can pass through glass without interfering with the amount of visible light transmitted. This works by refracting or deflecting UV and IR rays.

Laminated Glass

Also known as safety glass, this type of glass will not break apart when shattered, because it is held in place by a thin polymer interlayer, such as a cast in place (CIP) liquid resin between the glass’ layers. This type of glass is a safety glass which is used in architecture, glazing and in the automotive industry.

Mirrored Glass

This type of glass is made when a metal sheet is fixed behind the glass using a sealant. Although mirrored glass is not conventionally used as exterior windows, the reflective metal can be applied less densely. This is known as half-silvering, and it allows for one side of the window to be seen through, whilst the other side will reflect any incoming light.

Obscured Glass

Similarly, to float glass, obscured glass is a type of rolled glass which is modified after the initial process is completed of the molten glass being poured out onto a steel bed. The glass can then be obscured on its surface in multiple ways. One way this is done is by rolling the glass out using an engraved, patterned roller which causes the glass to mould into its small, engraved patterns to produce a desired effect.

Another method of obscuring glass comes after the glass has been set and cut. ‘Frosted’ glass is made when sheets of glass are dipped or etched in acid to create a pitted surface on one side of the glass pane. These glass panes are then affixed to each other, where the pitted, uneven surface face each other. Subsequently, this creates a smooth external glass surface whilst allowing light to pass through, yet still blurring what can be seen through the glass. These types of glass are also known as Stippolyte glass in the double glazing industry.

For the best results on the visual effects of obscured glass, our diverse showcase of uPVC doors highlights the importance of keeping your personal, indoor life from prying eyes.

Pressed Glass

Also known as patterned glass, this type of glass is made by pressing molten glass into a mould using a plunger. Although it is normally used to produce drinking glasses and furniture knobs, we can provide pressed glass on our door ranges.

Stained Glass

This type of glass refers either to coloured glass as a material or to works created from it. Although traditionally made in flat panels and used as windows, modern stained glass also includes three-dimensional structures and sculpture. Stained glass is glass which is coloured by adding metallic salts during its manufacture, and then decorating it further in various ways. The glass can be made into stained glass windows arranging shattered pieces of class into patterns or images, traditionally held together by strips of lead and supported by a rigid frame.

Tempered Glass

This type of glass (also known as toughened or safety glass) is strengthened using several techniques to produce glass which is four times the strength of annealed glass. When shattered, the glass will break up into granular pieces instead of shards. This involves the following steps:

As a preliminary measure, the glass is cut to its desired size, – rather than after the treatment process – as product failure can occur if any fabrication operations take place after its tempering. The glass is polished using an abrasive to remove any imperfections on the glass and is then subsequently washed.

Next, the glass begins a heat treatment process where it travels through a tempering oven. The oven heats the glass to a temperature of 620°C. The glass will undergo a high-pressure cooling procedure called ‘quenching’ which takes seconds. High-pressure air blasts the glass’ surface from an array of nozzles in all directions. Quenching cools the surfaces of the glass more rapidly than the centre. As the centre of the glass cools, it attempts to pull back from the outer surfaces. Therefore, the centre remains in tension, whilst the surfaces go into compression, which gives tempered glass its strength.

Wired Glass

Although generally perceived to be a type of security glass, wired glass is intended as a fire-resistant glass, and will prevent shards of glass breaking from the sheet in the event something collides into it. Wired glass tends to be less secure than unwired glass due to the incursions of the wire into the composition of the glass. Wired glass is crafted by placing a steel wire mesh into molten glass during its manufacturing process.

Overtime wired glass has become more obsolete as authorities have found this type of glass is, if anything, more dangerous and less secure than simple, annealed glass. For this reason, we do not provide wired glass. All our glass is certified by FENSA.

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