Short answer
The shape of the fade usually gives the cause away. Fading that follows a window, a fold or the exposed part of a curtain is light; sharp-edged spots and drips are chemicals such as bleach, peroxide or cleaning sprays; lighter areas at knees, seat fronts and arms are abrasion; even overall loss is washing. Faded dye does not return, so the practical goal is to stop it spreading and decide whether the piece can be re-dyed.
1. Uneven light exposure
Test: Look inside folds, under cushions, behind a seam or at the back of a curtain lining. If the protected areas keep the original colour and the pattern of fading follows the window, light caused it.
Fading depends on the total light a dye receives. The side facing a window, or the part of a curtain left undrawn, receives far more than the rest.
2. Chemical contact: bleach, peroxide, perspiration, deodorant or cleaning products
Test: Look at the shape of the marks. Splashes, drips and sharp-edged spots, or fading at underarms and collars, point to chemical contact rather than light.
Oxidising cleaners and some cosmetics attack dyes locally; perspiration can shift some dyes' colour.
3. Abrasion and rubbing wearing away surface colour
Test: Check whether the lighter areas are where the fabric is rubbed: seat fronts, knees, pocket edges, arms. Feel whether the pile or surface is worn there.
Some dyes, famously indigo, sit near the fibre surface and wear off with rubbing; worn pile also reflects light differently.
4. Washing: repeated washes removing a poorly fixed dye
Test: Compare the garment with an unwashed spare or the inside hem. Overall even lightening rather than patches suggests washing.
Dyes with poor wash fastness lose depth with each wash; uneven loading or folding in the machine can make it patchy.
Causes are ordered by how often Colourwise expects each to be the explanation — an editorial judgement, so test them all.
Unlike most colour problems, uneven fading leaves evidence in its geometry. Light fading has soft edges and follows exposure: the window-facing arm of a sofa, the leading edge of a curtain, the top of a folded throw, stripes where blind slats let sun through. Chemical damage has hard edges and odd shapes — splashes, drips, rings — and often an orange, pink or pale-yellow tinge where only one of several dyes was attacked. Abrasion follows wear: knees, pocket edges, cushion fronts, and it comes with a flattened or thinned surface you can feel. Washing loss is overall, with seams and folds sometimes slightly darker where the water moved less. Match the pattern first, then use the record's tests to confirm.
Textile dyes fade from the total light they receive over time, and that damage adds up and does not reverse. Conservation guidance puts it plainly: a textile at a hundred lux for four hundred hours is damaged as much as one at fifty lux for eight hundred. A sofa in a sunny window can receive many thousands of lux for hours a day, so fading that took years in the middle of a room can take a summer by the glass. Ultraviolet filters help but are not a cure — for light-sensitive colourants, visible light causes much of the fading and ultraviolet often only a small share. Drawing curtains or blinds during the brightest hours, rotating cushions and moving pieces out of direct sun all reduce the dose.
The light-exposure calculator estimates how long a colourant of a given sensitivity takes to reach a just-noticeable fade at a given light level — useful for judging whether a spot is safe for a favourite fabric.
Oxidising products — bleach, hydrogen peroxide in some cleaners and cosmetics, acne treatments containing benzoyl peroxide — attack dyes wherever they land, and the damage often appears only after the next wash. Many dyed fabrics are coloured by a mixture of dyes, so the attack removes one and leaves a spot of a different hue rather than a simple pale mark. Perspiration and some deodorants can change the colour of certain dyes at underarms and collars. None of these can be washed out. Small marks can sometimes be disguised by a textile-restoration or re-dyeing service; attempting to 'even out' a bleach mark with more bleach usually makes a larger mark.
Not by cleaning: faded or bleached dye has been destroyed, not hidden. The realistic options are acceptance, disguise or re-dyeing. Re-dyeing works best on natural fibres in a single colour and is unpredictable on blends, on polyester (which needs dyes and temperatures domestic dyeing does not reach) and on anything with contrasting stitching or trims. For upholstery and curtains, a new cover or replacing a panel is often simpler. For historic, antique or valuable textiles, involve a textile conservator before any treatment, because cleaning and dyeing can cause further irreversible change. And when buying for a sunny position, choose fabrics sold with good lightfastness ratings and line curtains.
Why: More oxidiser removed more dye around the original mark
Fix: Leave chemical marks alone and ask a textile-restoration service about disguise or re-dyeing
Why: Visible light also fades dyes and passes through the film
Fix: Reduce the total light: blinds in peak hours, rotate or move the piece, add lined curtains
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 does the same damage as 50 lux for 800 hours.
FactStrong evidence
For light-sensitive colourants, ultraviolet usually contributes less than half of the fading and often only about a tenth; visible light causes much of the damage.
Source: Agent of deterioration: light, ultraviolet and infrared
FactStrong evidence
Filtering ultraviolet does not stop fading from visible light, so UV films and glazing reduce but do not prevent colour loss.
FactModerate evidence
Indigo on denim has poor wash and rub fastness, which is why it wears pale where rubbed.
Source: Dyeing
Colourwise interpretationModerate evidence
The edge and location of a faded area — soft and exposure-shaped, hard-edged and splash-shaped, or wear-shaped — is the most reliable home indicator of whether light, chemicals or abrasion caused it.
Based on: Colourwise reading of how each mechanism acts: light acts on exposed areas in proportion to dose, chemicals where they land, abrasion where the fabric is rubbed.
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.