Glass Industry Visual Standards

What is the acceptable quality standard for toughened glass on my balustrade? Good question!

The glazing industry works to a prescribed acceptable visual quality standard for installed glazing. White Metal uses these visual quality acceptability guides to determine an acceptable level of glass installed on a balustrade, whether it be a frameless glass balustrade or a stainless steel and glass post system.

Avoiding disputes between our customers and the end client.

White Metal take pride in the quality of our products and aim to always exceed the glazing industry and the Glass and Glazing Federation’s (GGF’s) minimum quality standards but end users do need to understand the processes that are involved and the standards that there are in the industry.

We occasionally get a client complaining about a slight mark or imperfection on a glass panel when they are in fact inspecting it from an inch away, under torch light from their phone while moving from side to side!

Toughened Glass

This article, along with the PDF’s available on the GGF’s website will help avoid disputes between our customers and the end client.

A common sense approach needs to be taken and an understanding that modern processed glass is not going to be 100% flawless.

Checklist to undertake and explain when viewing glass.

When inspecting the glass, the following needs to be undertaken and explained to the end client:

  1. View the glass from inside the room standing a minimum of 3 metres away facing the glass. This is because under normal everyday situations, looking through glass is usually at a distance and not with your nose a few inches from the surface!

  2. Look through the glass and not at it. This is expected as normal as the glass is there to enable a view beyond the balustrade, not there to be inspected

  3. Do not inspect in direct sunlight. This is because the direct sun will be refracted by the coating and any tiny imperfections in the glass surface, highlighting items that cannot be seen in normal conditions.

  4. Ensure the glass is clean and dry inside and out. It is impossible to check glass that has rain, dust or condensation on it, mixing up these elements with potential problems.

  5. Ignore the 50mm perimeter of the glass. This is because when looking through panels, the eye is drawn to central areas and you doesn’t look through the edge of glazing when viewing. (Obviously large obtrusive marks in the perimeter are not acceptable.)

  6. Glass must be viewed at an angle of 90º.


What is the acceptable standard?

The GGF’s standards state that flat transparent glass, including laminated, toughened or coated glass is acceptable if the following are neither obtrusive nor bunched:

  • Bubbles or blisters

  • Fine scratches not more than 25mm long

  • Minute particles

Remember the obtrusiveness of blemishes is judged by looking through the glass, not at it, under natural light, from the distances mentioned above. It must be understood that the glass used on balustrades is a processed glass, toughened to a very high temperature, consequently some blemishes are to be expected.

Therefore, only blemishes that are intrusive to the view whilst inspecting glass under the above conditions are deemed as a defect. This may include marks in the coating, deep scratches that are clearly visible, multiple and clustered imperfections on the glass surface or processing marks such as fingerprints!


Other points of note:

Toughened glass may show visual distortions which are accentuated by reflections in sealed units and laminated panels. This is a natural phenomenon and not a fault.

Laminated glass may have a few more blemishes due to it being made of several layers.

Some low emissivity coatings may produce transient visual effects.

In some lighting conditions the coating may look like a transparent film or produce a haze, i.e. a cloudy look to the surface.

When light coloured objects such as net curtains are placed close to the glazing they may look slightly darker.

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