We follow the guidelines from the Glass & Glazing Federation, the industry authority, to inspect our glass (www.ggf.org.uk) to make sure the glass we use is installed to correct standards. Their Quality of Vision document provides details on how to carry out an inspection and what to look for:
How to do a Professional Inspection
– For toughened, laminated or coated glasses, stand no less than 3 metres away from the unit and look directly through it.
– Where it is not possible to stand at the right distance then stand as far away as you can from the sealed unit.
– Do so in natural daylight, but not directly towards the sun and with no visible moisture on the surface of the glass.
– Exclude 50mm wide band around edge of the glass from the check.
– Glass must be viewed at an angle of 90 degrees.
What to Expect when Carrying Out an Inspection
– 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
– The obtrusiveness of blemishes is judged by looking through the glass, not at it, under natural light. It must be understood that the glass used in sealed units is a processed glass, and as a consequence, blemishes are to be expected.
– Toughened glass may show visual distortions which are accentuated by reflections in sealed units. 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.
Source: Glass & Glazing Federation 2014