UV-filtering glazing: what it blocks and what it does not

Light damage depends on how intense the light is and how long the artwork is exposed. The Northeast Document Conservation Center (NEDCC) says damage is in direct proportion to the light level multiplied by the time of exposure [3]. The Canadian Conservation Institute (CCI) notes that UV is not necessary for seeing, except in rare cases of UV-fluorescent colours [1].

Sources differ in emphasis. NEDCC calls UV the most damaging part of the spectrum, but says visible light can also cause a great deal of damage [3]. CCI finds that for light-sensitive colours UV is the smaller share of fading, so both UV and visible light need control [1]. The wider background is in our pillar guide on light, UV and fading of printed artwork on walls.

UV filters come as glass, rigid plastic and thin flexible plastic film. Glass is used for windows and spotlights as well as for enclosures [2].

Performance varies widely. The CCI note reports average UV reductions by filter type, shown in the table below [2]. Ordinary glass cuts only part of the UV. Window glass filters short-wave UV, but CCI says not enough for museums [1].

The CCI note, citing Boye et al. (2010), reports that UV filter films were generally up to 5% less efficient than their performance claims [2]. It also cites ISO 18902:2007 as a recognised standard for evaluating UV reduction, with a recommended 97% reduction in the 300 to 380 nm range for protecting photographs, and, for acrylic sheet, ASTM D4802, which requires UV to be cut by at least 95% in the 200 to 390 nm range [2]. Asking for test data on the exact sheet, not only a product name, is a sensible extra step.

UV-filtering glazing does not remove visible light. NEDCC says visible light can fade colorants and dyes and can make paper fade, yellow or darken, and that the damage is cumulative and irreversible [3].

CCI adds one exception: for many artifacts, such as paintings with permanent pigments or monochromatic prints and drawings, UV-driven yellowing and disintegration of the media and support is the major form of deterioration suffered during uncontrolled museum lighting [1]. Whether a given printed piece belongs in that group is a question for the ink and paper, not for the glazing alone.

Intensity matters too. CCI notes that the rate of light damage rises 1,000 times from good museum light levels to sunlight [1]. NEDCC adds that low light over long periods can cause as much damage as high light over short periods [3].

UV filters do not last forever. In CCI's note, organic UV-absorbing compounds in glass, plastic panels and films degrade over time, while inorganic compounds in glass are expected to stay stable [2]. For UV films, CCI gives an expected useful life of 10 to 15 years when applied indoors [2]. Some films exposed to midday sun degrade much faster [2].

The film, the adhesive and the absorber can all wear [2]. CCI advises monitoring UV every few years, and says the rate of wear depends on heat, light and humidity [2]. Ask the maker for expected performance of the glazing sheet.

1. Cut intensity first. A wall that gets less light helps, and choosing walls that do not get direct sun is a practical way to do it.
2. Limit time. Shorter display periods reduce the exposure side of the rule in the first section.
3. Use a UV filter as a supporting layer, and ask for the measured UV reduction of the exact sheet [2]. For UV filter film, NEDCC says the only way to determine whether it is still filtering is to measure the transmitted light with a UV meter [3].
4. Check the glazing material for the room. Our guide on acrylic vs glass glazing covers weight, breakage and static, and our guide on frame materials covers the frame itself.
5. For hotel rooms, plan which walls get daylight; see our wall art plan for hotel rooms.
6. Record when filtering glazing was fitted, and plan to re-check it.

This guide is general information, not conservation advice for a specific object. Confirm product claims against the maker's test data.

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1. Agent of Deterioration: Light, Ultraviolet and Infrared, Canadian Conservation Institute, Government of Canada (Stefan Michalski). canada.ca (read 2026-11-08)
2. Ultraviolet Filters (CCI Notes 2/1), Canadian Conservation Institute, Government of Canada (Tetreault and Anuzet). canada.ca (read 2026-11-08)
3. 2.4 Protection from Light Damage, Northeast Document Conservation Center (NEDCC). nedcc.org (read 2026-11-08)