Inconsistency of Glass Colour
Example: Obvious colour variation in six adjacent panes of glass that should all look the same.
This page discusses why separate panes of glass in the same window can look different, and what to do to ensure that does not become a problem.
Glass can keep building occupants warmer or cooler, control noise & condensation, provide safety and protect our valuables from fading and maintain privacy, but each choice of glass can produce a slightly different colour, and that colour variation can become noticeable if not planned for.
Below we discuss:
- How to avoid colour variations in your project
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Why the following types of glass can be slightly different colours:
- Clear Glass
- Tinted Glass
- Laminated Glass
- Toughened Glass
- Reflective & Coated Glass
- Insulating Glass Units
- Understanding the technical reasons for the variations can assist with decision making.
How to avoid colour variations in your glazing project
- Purchase the entire project from the same supplier whenever possible.
- Discuss with your supplier/s your exact requirements and write them into the contract.
- Choose the best of all the solutions if a compromise for colour matching is required. The cost of re-glazing later will be far greater than getting it right the first time.
- Replacing Broken Panes:
- Alert repair staff of your colour matching requirements.
- Using the original suppliers will minimize colour matching issues as they are likely to have the original specifications.
Why the following types of glass can be slightly different colours:
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Most window glass is made from the “Float Glass” process but the mixture of raw materials can vary slightly. The most noticeable is the iron content and this can make some clear glass more green the others. The iron content can be reduced (low iron glass) to produce extra clear glass, but this is a more expensive.
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The inclusion of metal oxides creates tinted glass in a range of colours (bronze, grey, blue, green), but some manufacturers have slightly different formulations and tint colours. In general the bronze and grey colours are similar but the others can vary and may not be able to be matched.
In addition, the tint varies with the thickness and this adds further complications to colour matching.
Therefore, if you want tinted glass to match it should be all one thickness and from the same supplier for best uniformity.
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Clear laminated glass is very similar to clear monolithic float glass of the same thickness, and in most cases no colour variation is noticeable. However, it can happen in some lighting conditions.
Tinted PVB laminated glass does not match tinted float glass as it is the PVB interlayer that is tinted and not normally the glass. In addition there are several suppliers of tinted interlayer and their colours and appearance in certain lighting conditions can vary.
The laminate can be made with tinted glass to match if required, and some are offered in this format as standard.
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The toughening process does not alter the clear or tint colour but can introduce thermal stress patterns that are visible through polarized light.
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Coated glass colours do change when viewed at different times of the day, depending on the weather, surrounding reflections, building orientation and the angle at which the glass is viewed.
In addition the appearance of reflective glass is distinctly different if the coating is glazed outside on surface 1 or inside on surface 2.
The appearance of clear Self Cleaning and clear Low E coated glass is also slightly different to clear float but this is not normally significant.
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An IGU will not normally look different from monolithic glass if using the same outer glass. However, the introduction of a Low E can slightly increase reflectivity and the internal pressure changes in the unit can create flexing in the glass that changes reflected images.
In addition some rare visual effects are possible, such as Brewsters Fringes, which is a light refraction phenomenon seen as a rainbow effect, and Newtons Rings which is a circular rainbow effect evident when the panes are touching in the centre.
Example: Obvious colour variation in six adjacent panes of glass that should all look the same.