Phil Brown, European regulatory marketing manager at Pilkington United Kingdom Limited, part of the NSG Group, discusses how advanced glazing can be used to protect light-sensitive objects from fading in colour over time.
Keeping a treasured artefact or work of art safe so it can be enjoyed for generations to come means protecting it against every possible threat. That doesn’t just mean security concerns like vandalism and theft, but also the way the piece might react to the environment in which it’s kept.
Continued exposure to light – and, contrary to popular belief, not just the ultraviolet (UV) end of the spectrum – and oxygen will cause objects to fade in colour over time, which is particularly important in the fine arts, historical and heritage sectors. Over the course of decades, a painting or objet d’art on display can lose its colouration, often irreversibly diminishing its appearance.
High-value objects are also likely to be on display in commercial spaces – such as retail – and in the home, making it important to also consider how best to protect objects in these scenarios.
The speed at which fading occurs varies depending on the type and duration of exposure, controlling these factors in the right way can greatly reduce fading. The glazing industry, with its range of advanced, versatile coatings and interlayers, is well-placed to help collectors of all kinds, retailers and homeowners fight the fade.
How does light fade objects over time?
Continual exposure to light and oxygen alters an object’s chemical makeup - a process known as photodegradation.
A material’s colour is determined by its chromophores, referring to the part of a molecule that absorbs light. Chemicals naturally absorb light at different wavelengths, which determines the balance of colours reflected by objects and, in turn, how they appear to the eye.
Continued exposure to light, however, will reduce absorption from the chromophores, making an object appear more faded in colour. All sources of light – both natural and artificial – cause photodegradation, however direct daylight tends to have the strongest effect.
Specifying glazing to protect goods in different situations
While UV is often perceived as the main culprit in regards to fading, the transmission of the rest of the electromagnetic spectrum is just as important as the UV transmittance, particularly where there is glass with a high blue light transmission.
Generally, the shorter the wavelength of light, the more effective it is at fading materials. But it is also fair to say that the shorter the wavelength, the less light there is available, and proportionately less will be transmitted by the glass.
International standards have tried to address this by introducing more sophisticated parameters such as a ‘damage factor’ for materials. These evaluate the transmittance of different types of glass not only in the UV region but also for visible light. However, these have never really become established in the UK or mainland Europe and UV transmittance – with its known shortcomings - continues to be the most prevalent glass property quoted.
Specifications for glass to reduce fading still commonly refer to UV transmittance, with tinted glass generally allowing less UV light to pass through than clear, monolithic glass. In turn, laminated glass tends to block even more UV than tinted glass, due to the protective polyvinylbutyral (PVB) interlayer that is present in laminated glass.
However, the best glazing to specify will naturally depend on the context, location, and goods that need to be protected. In conjunction with the use of laminated glass, ideally incorporating a thick pvb interlayer, the design of the building needs to be such that the overall levels of illumination, exposure time and room temperature are reduced.
Public spaces such as galleries and museums
Photodegradation, and the associated loss of colour, can be disastrous for works of fine art.
Understandably, placing them behind glass may face opposition from art lovers, with some arguing that doing so compromises viewers’ ability to experience pieces by distorting the view or introducing reflections.
However, advances in glazing technology mean that this does not need to be the case. Special laminated glass could be used to protect artworks from fading, ensuring that works are saved from photodegradation, even incorporating an anti-reflective coating to avoid compromising on clarity of view.
Indeed, we recently provided anti-reflective laminated glass – Pilkington OptiView™ Protect OW – to protect a set of Italian masterpieces at an exhibition at Palazzo Te in Mantua, Italy, demonstrating the market for high-performance protective glass.
Reducing fading can also be a priority in commercial applications, particularly in the retail sector.
Clothing, jewellery and accessories are all examples of high-value items that may be displayed in a shop window to draw the eye of passing shoppers and drive footfall to the store. Unfortunately, these are also prone to fade with exposure to light, making it important to consider the makeup of the glass to protect the goods on offer.
Because a higher ambient temperature accelerates the fading process, solar control glazing products that regulate internal temperatures – such as the Pilkington Suncool™ – are a good way to ensure that in-store goods are protected from temperature effects on fading for longer periods. For optimal protection, laminated glass can be combined with a solar control coating to reduce both the transmission of UV and other parts of the spectrum, while enhancing the appearance of the products on display. So, not only will stock be protected, but it will also be better presented to potential customers.
Many people like to display their most valued objects in their homes. Whether the value of these items is financial or sentimental, owners will be very keen to preserve them from being damaged by the effects of fading.
No matter where an object is stored, defending it against fading is crucial in maintaining its long-term value. This is particularly important as glass continues to make up more of the building envelope, letting in more natural light.
After all, fading is permanent, and once colour is gone it’s gone for good, taking historical, financial and sentimental value with it.