Short answer
Textiles combine the most light-sensitive colourants — many natural and early synthetic dyes — with fibres that light also weakens, and the damage is cumulative and irreversible. Conservation guidance limits historic textiles to about 50 lux, ultraviolet below 75 µW/lm and display periods of around three months, because the most sensitive dyes can show a first visible fade after only a handful of such displays.
Textile colour is almost always dye, spread through the fibre as molecules, so every chromophore is exposed. Many dyes found in historic textiles sit in the Canadian Conservation Institute's high-sensitivity category, equivalent to blue wool 1–3. Light does more than fade: UV and visible radiation also cause photochemical damage to the fibres themselves, leading to yellowing and weakening. The Canadian guidance on textiles stresses that light damage is cumulative and irreversible and depends on total exposure: 100 lux for 400 hours does the same damage as 50 lux for 800 hours. Ultraviolet adds yellowing and weakening to the fading caused by visible light.
The table converts CCI's figures into three-month displays. A textile with dyes at the sensitive end of the high category may reach a just noticeable fade after about six three-month displays at 50 lux, and after only two at 150 lux; at 1,000 lux — a bright room near a window — a single display period can be enough. Medium-sensitivity dyes allow many more periods. This is why museums rotate textiles into dark storage, keep records of hours and illuminance for each piece, and treat each display as spending part of a finite light budget. For domestic textiles the arithmetic is the same: curtains, rugs and upholstery in sunny rooms receive thousands of lux for hours a day.
Fifty lux is dim, and CCI's textile guidance is candid that it suits young viewers looking at light-coloured objects with plenty of time. It suggests that each of four factors — older viewers, fine or low-contrast detail, dark-coloured objects and limited viewing time — can justify roughly three times more light. Taken together that multiplies to about 4,000 lux, far beyond what a sensitive textile could survive for long. Curators therefore balance visibility against preservation object by object, often using brighter light for short periods, better contrast between object and background, and adaptation areas so that visitors' eyes are ready for low light. The trade-off is a choice, not a rule.
Light is the main cause of fading, but not the only one. High humidity accelerates chemical deterioration and, above about 70% RH, invites mould, which stains; wet-cleaning a textile with unstable dyes can make colours bleed, which is why conservators check colourfastness first and never wash a textile whose colours have already run. Dust abrades fibres, and pollutants attack some dyes. In homes, the biggest avoidable risks are direct sun on curtains, rugs and upholstery and hot, damp conditions. Lined curtains, blinds drawn during bright hours, UV-filtering window film and rotating rugs and cushions all spread or reduce exposure, even if none of them stops fading altogether.
| CCI sensitivity | At 50 lux | At 150 lux | At 1,000 lux |
|---|---|---|---|
| High sensitivity | 6–82 | 2–27 | under 1–4 |
| Medium sensitivity | 82–2,885 | 27–962 | 4–144 |
Why: The exposed faces of the folds receive far more light than the recesses.
Fix: Line and interline curtains, draw blinds in strong sun, and consider UV-filtering window film.
Why: Direct light from one side, or a window reflection, gave some areas far more exposure.
Fix: Hang away from windows and direct lamps, use UV-filtering glazing, and rotate with storage.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactStrong evidence
Light damage to textiles is cumulative and irreversible and depends on total exposure: 100 lux for 400 hours causes the same damage as 50 lux for 800 hours.
Caveat: Reciprocity is a working approximation.
ConventionStrong evidence
CCI recommends UV no higher than 75 µW/lm for textiles, display for limited periods such as a three-month maximum, and records of display time and light level.
ConventionStrong evidence
CCI suggests that older viewers, fine or low-contrast details, dark-coloured objects and limited viewing time each justify about three times the 50 lux benchmark, giving about 4,050 lux if all four apply.
Colourwise analysisModerate evidence
A textile at the most sensitive end of CCI's high-sensitivity category reaches a just noticeable fade after about six three-month displays at 50 lux (8 hours a day), or about two at 150 lux.
Based on: Colourwise calculation from CCI's 1.5-year minimum at 50 lux and 3,000 hours a year, divided by the dose of a 91-day display at 8 hours a day; see the table.
Caveat: Category ranges are wide; a particular textile needs its own assessment.
Source: Agent of deterioration: light, ultraviolet and infrared
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.