FAQ's

Pure Vista specialises in balustrade systems, the gripping mechanisms that hold glass panels in place. We do not supply glass, however, most of your local glass suppliers or double glazing suppliers will be able to source suitable glass. Alternatively, we work with a number of reputable partners within the UK who may be able to help with this aspect of your project. If you are overseas, your local distributor may also be able to help.

Choosing the correct glass for your balustrade is paramount.  In any scenario, safety glass will always be required. Normally toughened glass is the standard option, this being up to 10 times stronger than the same thickness of clear annealed glass.

A second option is toughened laminate glass; this is when two panes of toughened glass are bonded together to form a single pane.  This offers the benefit that should one pane break, the other remains to safeguard any potential fall, plus it also reduces the potential of injury from falling glass.

Glass is toughened (tempered) by putting a cut to size piece of annealed glass through a kiln that heats the glass to molten point then rapidly cools the glass.  This causes compression on the outer surface thus increasing its strength.  Another benefit to toughened glass is that if it does break it shatters into very small pieces rather than large sharp shards.

One issue with toughened glass is a small risk of nickel sulphide (NiS) crystal forming within the glass, this can on rare occasions create a spontaneous breakage, which can happen at any time after installation.  The risk of this happening is greatly reduced if you ask for heat soaked glass, this is an added process where the toughened glass is re-heated to a reduced temperature and then cooled slowly.

Laminated glass consists of two sheets of glass bonded together with a special inter-layer between them. In respect of balustrade, it is normal practice to bond two panes of toughened glass together. There are many main types of inter-layer available, each has its own characteristics. The most common inter-layers include;

PVB = (Poly Vinyl Butyral) – Least resistant to water

EVA = (Ethyl Vinyl Acetate)

SGP = (Sentry Glass)

CIP = (Cast in Place)

Please be aware that laminate inter-layers can, if not installed correctly, be affected by immersion in water and can eventually cause de-lamination of the two sheets.  Laminated glass should never become submerged in water so depending on the location of your installation, appropriate drainage may be a required feature of your channel.

The table below shows details of the Uniform Distributed Load (UDL) and required glass make up for toughened and laminated glass for use on free-standing glass protective barriers (based on 1100mm high glass panels).

Annealed glass: often called float or sheet glass, is what you would expect to find in most houses’ windows, usually 4mm thick. It is relatively weak and easy to break – and when it breaks it does so in large, dangerous fragments. It should never be used in a balustrade installation as it would fail the line load test. As a general rule of thumb, any glass installed up to 800mm from the floor should be toughened.

Heat-strengthened glass: is when annealed glass is heated and cooled slowly. It is approximately twice as strong as annealed glass however, this treatment alone does not meet the required standards for balustrade. Like annealed glass, it breaks into large fragments which pose a risk of injury.

Toughened or tempered glass: is again, annealed glass. This time it is heated to a higher temperature and then rapidly cooled. This gives the glass far stronger properties, up to five times stronger than annealed glass. It can now withstand balustrade-appropriate impacts and passes the required testing. Above all, if this glass breaks, it breaks into small fragments rather than shards and therefore it is deemed safe for overhead breakage. When installing a balustrade this is the glass that must be used.

Heat soaked glass is when toughened glass is reheated and is slowly cooled. The reason for doing this is in toughened glass, there is a small risk of a nickel sulphide crystal naturally occurring in the glass during processing. The nickel sulphide crystal has a different expansion rate to glass so as glass heats and cools through the seasons, a spontaneous breakage may occur. This can be very costly if the glass is not easy to access post-installation. By heat soaking the glass, this risk is drastically reduced and if a breakage happens in the factory during processing, another panel can be produced.

Wet glazing is the accepted term for a resin set balustrade system. It is when the glass is placed into, most commonly a standard U-shaped channel and a resin is poured into the system. It is then left to harden which can take many hours. The time delay can be an issue since wind (or any other force against the glass) could push the glass out of line. Other pitfalls with wet glazing systems are that if the wrong resin is used, there is potential for issues further down the line as some ingredients react with certain glass types. Also, the variance in expansion rates can allow for cracking around the edges. The biggest problem with a full wet glaze balustrade is if there is ever a reason for deglazing (such as a broken panel or glass thickness change), it is no easy feat removing glass that has been fully set with resin. For these reasons, all Pure Vista products have been designed to be dry-glazed – although some of our products can be wet glazed, if required.