Toughened glass is a heat tempering process, which in turn places the centre of the glass pane under tension, whilst the surfaces are under compression. This produces a highly versatile material that can even be utilsed in point loaded applications or for structural glass beams.

 

Due to the heat tempering process, the surfaces our less scratch resistant than normal float glass, which in turn allows for greater movement within its weakest plane before fracturing.  Its breakage characteristics however, do result in the glass simultaneously fracturing into small fragments. These in turn are typically considered safe or nonfatal up to a height loosely based upon two stories above the finished floor below (due to the lack of momentum accumulated). Whilst it is the density of fragments that is controlled, due to there irregular shape these can sometimes ‘cluster’ together. Whilst toughened glass has offered huge advancements in modern day glass technology, it is particularly more vulnerable about its edges.     

 

All toughened glass within the UK should be kite marked to indicate its modern day compliance during fabrication to BS EN 12150. This may either be stamped onto the face or the edge of the glass. The certification of compliance indicates, insures that controlled conditions are maintained and as a result (and whilst ‘clusters’ can not always be controlled), the glass will break into a specific density of fragments.

 

Whilst considered a safety glass toughened glass can not always be utilsed without the utilisation of laminate and sometimes float glass within the specification. In many applications its breakage characteristics should not be ignored as in the future event of accidental or deliberate breakage, boarding and security considerations will need to be considered. It is considered good practise to always consider the use of laminate in such applications such as overhead canopies.

 

Glass during its production can be contaminated with impurities such as nickel sulphide (or nickel sulphide inclusions). Due to the forces toughened glass is under in its natural state, additional forces through deflection (and general loading), vibration and expansion can result in localised fracturing and subsequent over all fragmentation of the glass.

 

All glass that is supported from a point fixed frameless glazing system or subject to adverse loadings should be heat soak tested. This is a process where once the glass has been toughened; the glass is subject to heat testing, which in turn will identify any contamination within the glass by its complete failure (in which case the glass will need to be remade). Whilst contamination to modern day standards is rare, heat soak testing is an additional process and subsequently contributes proportionally to the cost of contemporary glass design.

Laminated Glass equally has an important role in modern day architecture. Whilst in float glass form it is not as versatile as toughened glass, it does have enhanced properties for consideration. Whilst utilised with float glass (sometimes combined with toughened glass), laminated glass is structurally more suitable for retaining itself under impact/breakage (and is therefore a typical requirement of a ‘man safe’ specification).

 

Additional benefits of laminated glass include:-

 

Additional Security with Retained Breakage Characteristics
(typical for applications where a ‘man safe’ specification is required)

 

Over 99% UV Light Reduction
(particularly useful with art , furnishings and fabrics that will fade over time)

 

Significant Sound Reduction
(made more noticeable in single glazed form)

 

The Inherent Structural Benefits of Laminates
(by there nature provide individual structural advantages and reduce all forms of vibration)

 

There are two main types of laminated glass within the market.

 

The first is a process of sandwiching sheets of glass over a Poly Vinyl Butyral (PVB) interlay and applying pressure. Common interlay thicknesses are 0.38mm and 0.78mm. This method is originally carried out with large laminated sheets for cutting down to application. PVB interlayer’s may react with acidic silicones and delaminate under continued contact with water.

 

A ‘Cast in Place’ CIP laminate is now more commonly being utilised. During this process two or more sheets of glass (toughened or float) are laminated together by the application of resin between each sheet. 1.0mm and 1.5mm interlayer thicknesses are common for CIP glasses. In these instances where an obscured glass is required, a softer light may be experienced by incorporating a white laminate.

 

It is also possible to have glass laminated with a liquid crystal and polymer matrix. Combined with conductive coatings, the glass will become transparent once a current has been applied and obscured in its natural state.

The contemporary glass market and designs have evolved incredibly since the developments surrounding toughened laminated glass were introduced. Primarily due to their combined structural properties, a toughened laminated specification allows glass to be utilised structurally as never before in architecture.

 

Whilst sometimes utilsed on framed glazing (due the expediential structural thickness requirement of float laminated over larger spans), Toughened laminated glass is more often utilised in frameless glazing and structural glazing applications.

 

Toughened glass is also often laminated with float glass within a specification. The combined properties of the two are desirable on some walk-on glass specifications and overhead canopy applications.

Float glass (other than when laminated) is generally not acceptable within any of the products and designs we supply. Its breakage characteristics and subsequent shards of glass could result in a fatal accident and is generally only found within dated domestic applications.

 

We have provided this section purely as an aid primarily for the identifying of broken glass specifications and should you be replacing float glass; a safety glass specification should be reviewed accordingly.

 

Should you be removing or handling any forms of broken glass (especially float) a specialist should be contacted and the necessary PPE (personal protective equipment) be worn.

Tinted glass is often disregarded in architectural glass design. More often a contemporary design is required and enthuses placed on the structure being as frameless and translucent as possible. Often the design brief is to allow as much natural light into the associated environment.

 

There are hundreds of tints available in glass from more architecturally natural tints (greys, blacks, greens and bronzes) to irregular tints (blues, yellows, purples, pinks and reds).

 

Tinted glass can be utilsed to control the environment internally as the light transmittance and heat transmittance of each varies. They are also an excellent way to emphasise glass in architecture and by their nature, have varying effects on the light spectrum reflected and transmitted.

 

Due to its iron content, standard clear glass contains its own natural green tint. Whilst this is not so noticeable over typical glass thickness, this tint does darken when looking through a thicker prism. In applications that utilise thicker glass specifications or when the edges of the glass become an aesthetical feature (structural glass balustrade and structural glass fins), you may wish to review a Low Iron glass specification.

As with tinted glass, glass coatings are also able to contribute to the reflection and transmission of heat and light. Due to the modern day building regulations, coated glass is nearly always required in double and triple glazed applications.

 

Standard Low E tends to be the basic coating requirement (Double Glazed Mid Pane U-Value of approx. 1.7W/m sq K); however a ‘Super’ Low E coating has more recently been developed for further improvement (Double Glazed Mid Pane U-Value of approx. 1.4 W/m sq K).

 

In these instances a further 0.1 – 0.2 W/m sq K reduction can be achieved by having argon applied to the glass cavity.

 

We are often asked on larger structures to provide glass coatings such as the Pilkington’s HP Suncool (neutral) or equivalent. Not only does this coating have a starting Mid Pane U-Value of 1.3W/m sq K within a standard double glazed unit, but it also provides brilliant reductions in heat gain (ensuring glazed areas are more inhabitable during the summer months).

 

Glass coatings are not only utilised to control the environment within a glazed structure. There are many other coatings available in today’s industry, which assist with other considerations such as maintenance, cleaning and even obscurity.  

Once your specification has been technically established to achieve building regulation requirements and meet the technical requirements of the design. You may wish all or part of the glass to be provided with additional finishes.

 

Sandblasting and Acid etching of glass are two very different processes. They do however provide a similar appearance. With either finish, it is possible obscure the glass by the etching of one of the glass surfaces. The etched surface then diffuses the light making it very difficult to see any objects outside of the immediate proximity of the glass itself. Sandblasting and acid etched glass can be an excellent way to obtain natural daylight, whilst maintaining an enclosed/private space. There are however a couple of important considerations. In its natural state, the etched surface will easily retain dirt and grease (typically from finger prints). In addition and should the etched surface become wet, the glass will become more transparent due to a reduced diffusing of the light. Both of these issues can be overcome by either applying a coating after production or in the instances of double/triple glazed units, not having the etched faces exposed after assembly (i.e. facing the glass cavity).

 

 Alternatively, you may wish the glass to be obscured with a ceramic coating, which is ‘baked’ onto the surface during toughening. This process can be utilsed to achieve additional friction (an option adopted for walk-on glass rooflights/floors) or obscurity locally over any framework etc. Ceramic Glass Coatings are provided in any standard colour within RAL range (see Polyester Powder Coating, System Finishes).

 

Glass finishes can typically be applied over a whole glass unit, regularly within part of a unit (i.e. manifestations etc.) or to a detailed design (i.e. logo and creative glass developments).

Hermetically sealed glass units are produced in double glazed and triple glazed applications. During assembly a spacer bar is installed to the cavity and once all individual panes have been assembled a sealant is applied about the unit’s perimeter. Any moisture is then removed from the cavity, producing a dry air gap.

 

Once a dry air gap has been established, the air may sometimes be flushed out of the unit and replaced with a range of other gases (typically argon) to achieve improved thermal and acoustic performance.

 

In general the installation of double glazed and triple glazed units drastically reduces the associated cold bridging, which in turn is partly responsible for any level of condensation to the glass (in addition to humidity). Traditionally, the majority of cold bridging over a double glazed unit occurs over the perimeter spacer bar detail. This too can be drastically reduced with the introduction of warm edge spacer bars (which are common place in modern architectural glass designs).