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What went wrong with this colour?
A colour that has changed has usually done one of 15 things, and several of them look alike. A paler surface may have faded, chalked or merely lost its gloss; a yellowed one may be stained. Start from what you can see, check it against its look-alikes, and only then decide what to do — because the remedies differ and some changes cannot be undone.
Start with the symptom
Symptom to cause: the failures at a glance
What you see
What it is
Can it be reversed?
First thing to do
The colour has become paler, or has shifted hue, on the side that faces the light.
Usually none: let an uneven young patina even out with time
Marks, streaks or an overall darkening that came from outside the material: rust spots, tide marks, dark streaks under sills, green run-off, grey grime.
Repaint or replace to the nearest corner or joint, not a patch
Beyond a colour change, the material itself has deteriorated on its sunlit face: brittle or cracked plastic, a powdery coating, weak silk, grey fibrous wood.
Recoat or refinish once the degraded layer has been removed
Discolouration beside a heat source: yellowed paint above a radiator, rainbow or straw tints on stainless steel, colour moved from one fabric to another, a warped or yellowed plastic part.
Dull marks on polished stone, a rough pale face on cleaned brick, worn-pale seams and edges on fabric, shiny scrubbed patches on a matt wall, chips through enamel.
Rewash a fabric promptly, separately, before it dries
For a guided route through one specific problem — a wall, a fabric, a metal fitting — use the colour problem diagnostic.
Each failure in detail
Fading
What you see: The colour has become paler, or has shifted hue, on the side that faces the light.
Can it be reversed? Irreversible. The colourant is destroyed, not hidden. Colour returns only by re-dyeing, repainting or retouching — that is, by adding new colourant.
Why it happens
Light breaks or alters the colourant molecules so that they stop absorbing. In a mixture the least stable colourant goes first, which shifts the hue rather than simply lightening it.
What drives it
Total light dose: brightness multiplied by hours
Ultraviolet, out of proportion to its share of the light
Visible light alone, for sensitive dyes
Heat and air pollutants, which add routes that need no light
How to recognise it
Compare with an area the light never reached — under a mount, a hem, a cushion or the back of the object. The change follows exposure, has soft edges and affects only the lit face.
Easily confused with
Chalking. Wipe the surface: chalk comes off as powder and the colour beneath is stronger; a faded surface stays pale.
Gloss loss and burnishing. Wet a small area: if the colour deepens while wet, the surface has roughened rather than the colourant gone.
Cleaning, abrasion and impact damage. Wear follows seams, edges and handling; chemical damage has hard, splash-shaped edges; light fading follows the light.
What to do now
Accept, or renew the colour: repaint, re-dye or reupholster
For valued objects, keep the original in low light and display a copy
How to prevent it
Lower the light level and the hours of exposure; the damage depends on the product of the two
Filter ultraviolet, knowing that this slows fading without stopping it
Choose colourants rated for lightfastness where sun is unavoidable
What you see: A white, a pale colour or a clear coat has turned cream, yellow or brown.
Can it be reversed? Partly reversible. Whether the yellow is in a layer that can be removed or renewed — a varnish, a coat of paint — or in the object's own substance, as with paper, plastic and silk, where it stays.
Why it happens
The material itself — binder, resin, fibre, paper or plastic — oxidises and forms products that absorb blue light. The colourant may be untouched; it is the body it sits in that has changed.
What drives it
Ultraviolet, for plastics, resins, wood and silk
Darkness and warmth, for oil and alkyd paints and varnishes
Heat generally, which speeds every oxidation
Acidity and lignin, in wood-pulp paper
How to recognise it
The shift is towards yellow or brown and is strongest in whites and clear layers. Note where it is worst: on the sunlit face, or — for oil and alkyd paint — in the places light never reaches.
Easily confused with
Staining and soiling. Soiling and nicotine wipe or wash off, at least partly; a yellowed material is the same colour after cleaning.
Fading. Fading loses colour; yellowing adds one. A yellowed white is darker than it was, a faded colour is paler.
What to do now
Repaint or recoat a yellowed finish
Leave removal of a yellowed varnish on a painting to a conservator
Replace yellowed plastic parts; surface treatments do not restore the material
How to prevent it
Water-borne paint rather than oil or alkyd where whiteness matters, above all in unlit places
Ultraviolet-stabilised grades of plastic and resin for sunlit and exterior use
Photo-oxidation of lignin and extractives (indoors)
Pale woods yellow or brown; some dark woods fade first
UV and violet light
UV-absorbing finishes, rotate rugs and objects, blinds
Strong evidence. Light drives yellowing in some materials and its absence drives it in others, so the pattern on the object, not a general rule, identifies the cause.
What you see: A material that was never dyed or painted — above all timber — has gone paler or grey where light and weather reach it.
Can it be reversed? Partly reversible. Depth. The change is confined to a thin surface layer, so removing that layer exposes unaltered wood — which then begins to change in its turn.
Why it happens
Light breaks down the natural coloured components of the material. In wood, darker species can lighten as their extractives are destroyed, and outdoors the degraded lignin is washed away, leaving a grey surface of cellulose fibres.
What drives it
Ultraviolet and violet light
Rain, which washes out the degraded lignin outdoors
Mould on damp weathered wood, which adds a darker grey
How to recognise it
The change is in the surface fibres of the material itself, not in a coating. It follows exposure, and a covered or shaded area keeps the original colour.
Easily confused with
Fading. Fading destroys an applied dye or pigment; bleaching changes the material's own colour, so it shows on unfinished and clear-finished wood.
Yellowing. The same light yellows or browns pale woods and lightens dark ones, so both can appear on one piece of furniture made of two timbers.
What to do now
Sand or plane back to unweathered wood and refinish
Leave weathered grey as a finish where it is even and wanted
How to prevent it
Pigmented stains or paint outdoors; clear finishes alone do not protect for long
Ultraviolet-absorbing finishes and blinds indoors
Move rugs and objects so that exposure is even
Bleaching of a material's own colour: how it shows on each material
What you see: Bright metal has gone dull, yellowish, brown or black.
Can it be reversed? Partly reversible. The film can be removed, but each polish or dip takes some metal with it and leaves fine scratches, so plated and decorated pieces cannot be cleaned indefinitely.
Why it happens
The metal surface reacts with gases in the air to form a thin film of a coloured compound: black silver sulphide on silver, dark copper oxide and sulphide on copper and its alloys.
What drives it
Sulphur-containing gases, for silver
Air and moisture, for copper, brass and bronze
Handling: salts and oils from skin mark the surface
How to recognise it
A thin, even or fingerprint-patterned darkening of bare metal that polishing removes. Where a lacquer has failed it is patchy with sharp edges.
Easily confused with
Patina. Tarnish is the early thin film; patina is the thicker, stable layer that develops over years, such as the green on outdoor copper.
Staining and soiling. Dirt washes off with detergent; tarnish needs a polish or a chemical dip.
What to do now
The mildest polish that works, used rarely
Local application of a chemical dip rather than immersion, for silver
Accept the darkened surface as the metal's settled colour
How to prevent it
Sealed storage with a tarnish-absorbing material, for silver
Gloves when handling polished metal
Lacquer or wax on copper alloys, applied evenly — a patchy coat tarnishes worse than none
Tarnish and oxide darkening: how it shows on each material
Strong evidence. Silver has no record of its own in the materials dataset; the guidance on it comes from conservation practice for objects, which is stricter than household care needs to be.
What you see: A metal or leather surface has settled into a new, stable colour: green on copper, dark brown on weathering steel, a deeper tan on leather.
Can it be reversed? Partly reversible. It can be stripped back to bare metal, but that removes material and the layer starts to form again; on weathering steel the layer is the protection and is not meant to be removed.
Why it happens
Corrosion products or oxidised material build into a layer that adheres to the surface. On copper outdoors a thin inner oxide lies under a thicker green layer of basic copper salts; on weathering steel a dense rust layer forms and slows further rusting.
What drives it
Years of outdoor exposure
Alternate wetting and drying, which weathering steel needs
Sulphur compounds or sea salt in the air, which decide which copper minerals form
Light, air and handling, for leather
How to recognise it
A coherent layer that does not rub off as powder and follows how water runs and dries on the surface. Often intended: it is the finish, not a defect.
Easily confused with
Staining and soiling. A stain is one material's product deposited on another; patina forms on the material it comes from. Green streaks on stone below copper are a stain, the green on the copper is patina.
Strong evidence. The sources cover copper roofing and structural weathering steel. The account of leather is in the materials dataset and is not sourced to the same standard.
What you see: Marks, streaks or an overall darkening that came from outside the material: rust spots, tide marks, dark streaks under sills, green run-off, grey grime.
Can it be reversed? Partly reversible. What the stain is and how far it has gone in. Surface soiling cleans off; a stain absorbed into porous stone or reacted with the material may only lighten, and the cleaning itself can do damage.
Why it happens
A foreign substance is deposited on the surface or drawn into its pores, or reacts with the material: airborne dirt, iron from fixings, copper from metalwork above, tannins meeting iron in damp wood, oils and organics soaking into stone.
What drives it
Porosity: an open surface draws in whatever is on it
Water, which carries dirt, salts and metal compounds and decides where they are left
Roughness, including roughness made by harsh cleaning
Iron or copper in contact with, or above, a porous or tannin-rich material
How to recognise it
The pattern follows a source and a path: below a fixing, under a drip, along a run-off line, around a spill. The surrounding material is unchanged.
Easily confused with
Yellowing. A stain has a boundary and a source; yellowing is general and follows light or its absence.
Efflorescence. Efflorescence is white, crystalline and brushes off dry; most stains are coloured and do not.
What to do now
Identify the stain before treating it; the wrong cleaner can set it or etch the surface
The gentlest method first, tried on a small area
Oxalic acid for iron–tannin marks on wood; a poultice for absorbed stains in stone
How to prevent it
Stainless or non-ferrous fixings in stone and tannin-rich wood
Drips, sills and gutters that keep run-off away from porous surfaces
Impregnating sealers on porous stone — they resist staining rather than prevent it
Staining and soiling: how it shows on each material
Fine crack network that picks up tea, dirt or grout colour
Glaze–body expansion mismatch and moisture
Well-fitted glazes; vitrified bodies
Strong evidence. A broad class: the right treatment differs for each kind of stain, and specialist advice is warranted on valuable or historic surfaces.
What you see: A sharp-edged patch of different colour where a rug, picture, piece of furniture or mount used to be.
Can it be reversed? Partly reversible. The exposed area cannot be returned to its earlier colour. Because the change is cumulative, uncovering the protected patch lets it change too, which may narrow the difference without removing it.
Why it happens
Light-driven change depends on the total dose each area has received. An object that shades part of a surface leaves that part less changed — or, for materials that yellow in the dark, more changed — than its surroundings.
What drives it
An object left in one place for a long time
Strong directional daylight
Oil or alkyd paint behind pictures and furniture, which yellows where light is kept off
How to recognise it
The outline matches something that was there. This is the clearest evidence of how far the rest of the surface has moved, because the patch records the earlier colour.
Easily confused with
Staining and soiling. A stain adds something that can be felt or cleaned; a shadow patch is the same surface, cleaner-edged, with nothing on it.
Moderate evidence. The sources establish that the change depends on dose and on the presence or absence of light. That a protected patch will catch up is an inference from that, and no source gives a time for it.
What you see: A gloss surface has gone dull and looks paler, or a matt surface has developed shiny patches that look darker.
Can it be reversed? Partly reversible. Only the surface is affected, so a new coat restores it; but a burnished patch cannot be made matt again, and touching up a patch rarely matches the sheen around it.
Why it happens
Gloss lives in the top of the film. Weathering and scratching roughen a smooth surface, so its reflection scatters and veils the colour; rubbing does the opposite to a matt surface, smoothing it so that the patch reflects like a higher sheen. The pigment is unchanged in both cases.
What drives it
Sunlight, oxygen, heat and moisture acting together on an exterior coating
Abrasive cleaning and scratching of gloss surfaces
Rubbing, scrubbing and furniture contact on flat paint
How to recognise it
View the surface along its length against the light: the change is in how it reflects, not in its colour face-on. Dark colours show it most.
Easily confused with
Fading. Wet the dulled area: a gloss loss deepens back towards the original colour while wet, a faded colour does not.
Chalking. Chalk transfers to a finger or a dark cloth; a dulled but sound film does not.
What to do now
Repaint the whole wall section or panel, not the patch
Clean an exterior coating first: part of the dullness may be dirt and chalk
How to prevent it
A higher-sheen, more durable finish where walls are touched and cleaned
Soft cloths and non-abrasive cleaners, and time for new paint to harden before it is washed
Coatings rated for exterior durability outdoors
Gloss loss and burnishing: how it shows on each material
Strong evidence. Sheen names are not standardised, so 'matt' from one maker may burnish more readily than 'matt' from another; no source ranks products.
What you see: A fine pale powder on an exterior paint, powder coat, gelcoat or plastic; the colour beneath looks washed out.
Can it be reversed? Partly reversible. The loose powder can be cleaned off, which recovers some colour, but the binder that has eroded is gone and the surface will chalk again.
Why it happens
Ultraviolet breaks down the binder or polymer at the surface. Pigment particles that it held are left loose, and the loose powder scatters white light over the colour.
What drives it
Sunlight, most on the faces that receive most of it
Binders and pigment grades not made for exterior use
Photoactive white pigment, which speeds the breakdown of the binder around it
How to recognise it
Rub a fingertip or a dark cloth across the surface: chalk transfers. This is how the standard test methods assess it.
Easily confused with
Fading. Wash a small area. If the colour underneath is close to the original, the paleness was chalk; if it is still pale, the pigment has faded as well.
Efflorescence. Efflorescence is salt from the wall behind and appears in patches where water moves; chalk is the coating itself and is even over the exposed face.
What to do now
Wash off the chalk to see what colour remains
Clean the chalk off before recoating
How to prevent it
Exterior-grade coatings; architectural-grade powder coat or fluoropolymer on metal
Weathering grades of plastic and stabilised gelcoat
What you see: New material does not match old, or two deliveries of 'the same' colour differ: a visible line where one tin, lot or pack ends and the next begins.
Can it be reversed? Partly reversible. Nothing brings two batches together; the mismatch is removed only by re-coating or replacing up to a natural break such as a corner.
Why it happens
Every colour is made to a tolerance, so two production runs differ slightly from the start; and installed material goes on ageing, so a replacement is being matched to a colour that has since moved.
What drives it
Separate production runs, firings or dye lots
Factory-made beside in-store-tinted paint, or two makers' versions of one colour
Alloy and process differences in anodised aluminium
Time: the installed surface has faded, yellowed or soiled since it was new
How to recognise it
The difference follows a joint, a panel, a course or a wall — the boundary between two supplies — and is there from the first day or from the day of the repair.
Easily confused with
Uneven ageing and shadowing. Shadowing follows the outline of an object and develops over time; a batch difference follows a joint and is immediate.
Gloss loss and burnishing. Look face-on and then along the surface: a difference seen only at an angle is sheen, not colour.
What to do now
Repaint or replace to the nearest corner or joint, not a patch
For tile and other units sold with a stated variation class, look at several pieces together before laying, not one
How to prevent it
Buy enough from one batch number, lot or firing for the whole visible area
Where batches must change, change at a corner or other break
Approve range samples that show the lightest and darkest acceptable pieces
Keep some of the original batch for repairs, and expect even that to differ from an aged surface
What you see: Beyond a colour change, the material itself has deteriorated on its sunlit face: brittle or cracked plastic, a powdery coating, weak silk, grey fibrous wood.
Can it be reversed? Irreversible. Broken polymer and fibre cannot be mended. A damaged surface layer can sometimes be removed or recoated, which is replacement, not repair.
Why it happens
Ultraviolet photons carry enough energy to break bonds in polymers, lignin and fibre proteins that visible light leaves alone, starting oxidation in material that carries no colourant at all.
What drives it
Direct sun and unfiltered daylight
Heat and moisture, which speed the reactions ultraviolet starts
Loss of stabilisers from older plastics
How to recognise it
A change of texture or strength as well as of colour, confined to the exposed face, on materials known to absorb ultraviolet.
Easily confused with
Fading. Fading alters the colourant and can happen under visible light alone; ultraviolet damage alters the substrate and usually shows as yellowing, chalking or weakness.
Heat damage. Heat damage does not need light and appears beside the heat source; ultraviolet damage follows the light.
What to do now
Recoat or refinish once the degraded layer has been removed
Replace embrittled parts
How to prevent it
Ultraviolet-filtering glazing or film, which costs nothing in visible light
Stabilised grades, pigmented finishes and shade for exterior materials
Pigmented rather than clear finishes on exterior wood
Ultraviolet damage to the material: how it shows on each material
What you see: Discolouration beside a heat source: yellowed paint above a radiator, rainbow or straw tints on stainless steel, colour moved from one fabric to another, a warped or yellowed plastic part.
Can it be reversed? Irreversible. Distorted plastic, migrated dye and a thermally yellowed material do not go back. Paint can be renewed, and will yellow again if the heat remains.
Why it happens
Warmth speeds every chemical route to discolouration. At higher temperatures it does more: it thickens the oxide film on stainless steel into interference colours, drives some dyes out of synthetic fibres, and softens and distorts plastics.
What drives it
Radiators, stoves, heating ducts and lamps close to a surface
Direct sun on dark surfaces, and more so behind glass
Welding and other hot work on stainless steel
Hot ironing, drying and storage of dyed synthetics
How to recognise it
The change is centred on a heat source and fades with distance from it, and it occurs with or without light.
Strong evidence. Heat-tint colours on stainless steel depend on the alloy, the time, the atmosphere and the finish, so a colour does not identify a temperature. How to remove heat tint was not sourced and is not covered.
What you see: Dull marks on polished stone, a rough pale face on cleaned brick, worn-pale seams and edges on fabric, shiny scrubbed patches on a matt wall, chips through enamel.
Can it be reversed? Partly reversible. Whether there is material left to refinish. Etched marble can be re-honed and repolished by a specialist; the fired face of a brick or a worn plated layer cannot be put back.
Why it happens
The surface that carried the colour or the finish has been removed or reshaped: acid dissolves calcite, abrasives strip the fired face of brick and the polish of stone, rubbing wears dye and fibre away, polishing takes metal with the tarnish, and an impact breaks a glass layer off its metal.
What drives it
Acidic cleaners and spills on marble and limestone
Sandblasting and other abrasive cleaning of masonry
Abrasive cleaners and frequent scrubbing of flat paint
Grit underfoot on stone floors
Repeated washing and wear of dyed fabric
How to recognise it
The pattern follows contact: where a glass stood, where a cloth was rubbed, along seams and edges, across the whole face that was blasted. The change can usually be felt as well as seen.
Easily confused with
Fading. Wear is local to contact and edges and can be felt; light fading follows the light and leaves the surface texture unchanged.
Staining and soiling. An etch mark is a change of sheen with no added colour and does not clean off; a stain adds colour.
What to do now
Professional refinishing for etched or scratched stone
Repaint a burnished wall section
Accept abrasive damage to masonry; further cleaning makes it worse
How to prevent it
Neutral cleaners on calcareous stone; mats and regular dusting to keep grit off floors
The gentlest method that works on masonry, and no abrasive blasting
Soft cloths and mild cleaners on painted walls
Polish metal rarely, and with the mildest polish
Cleaning, abrasion and impact damage: how it shows on each material
What you see: A white, powdery or crystalline bloom on brick, concrete, render or plaster.
Can it be reversed? Reversible. The moisture. The salts are water-soluble: much of the bloom on new work goes with normal weathering and the rest brushes off, but it returns for as long as water keeps entering.
Why it happens
Water moving through masonry dissolves salts and carries them to the surface, where it evaporates and leaves them behind as crystals.
What drives it
Water getting into the wall during or after construction
Soluble salts, mostly from mortar and adjacent concrete
The first year of a new building
How to recognise it
White, patchy, strongest where water gets in or dries out, and most visible on dark units. It brushes off dry and may return after the next wetting.
Easily confused with
Chalking. Chalk is the paint itself and covers the weathered face evenly; efflorescence comes through from the wall and appears where moisture moves.
Staining and soiling. Efflorescence is white, water-soluble salt that brushes off dry; a stain is usually coloured and does not.
What to do now
Dry-brush; washing is advised against except in warm, dry weather
Find and stop the water before redecorating
How to prevent it
Keep masonry dry during and after construction
Details that shed water and stop it entering the wall
What you see: Colour has moved: a halo around a printed edge, a tint picked up by a neighbouring fabric, a print that has left its ghost on the facing page.
Can it be reversed? Irreversible. The dye has bound to its new place. Immediate rewashing sometimes lifts fresh transfer from a fabric, but nothing reverses bleed within a print.
Why it happens
A dye that is not firmly bound becomes mobile in water, in high humidity or with heat, and moves sideways, through the material or onto whatever touches it.
What drives it
Washing, wetting and high humidity
Heat, which mobilises the disperse dyes used on polyester
Dye-based inks and loosely fixed dyes; pigment colourants move far less
How to recognise it
Colour appears where there was none, next to its source, in the colour of that source. The source itself may look only slightly paler.
Easily confused with
Staining and soiling. A transferred dye matches a neighbouring coloured area exactly; other stains do not.
Fading. Fading destroys colour; migration relocates it, so it turns up nearby.
What to do now
Rewash a fabric promptly, separately, before it dries
For prints and valued textiles, none: prevention is the only control
How to prevent it
Test for colourfastness before wet cleaning; any transfer in the test rules out washing
Keep prints and dyed textiles dry and cool, and out of contact with each other
Moderate heat in ironing and drying of dyed synthetics
Dye bleeding and transfer: how it shows on each material
Each entry is one record in Colourwise's colour-failure dataset: symptom, mechanism, drivers, how to recognise it and what it is confused with, reversibility, prevention and remedy, with its sources and a caveat.
The per-material tables are not written for this page. They are the ageing rows of the materials dataset — 43 of its 44 rows are classified under at least one failure here — so a material page and this guide cannot contradict each other.
Reversibility is one of three verdicts, always with what it depends on, because the honest answer is rarely a plain yes or no.
Limitations
It describes mechanisms and published guidance. It is not an assessment of a particular object, and valued or historic surfaces need a conservator or a specialist.
The tests for telling failures apart need no instruments, and so they are indicative. Two failures often occur together: an old exterior paint is usually chalked, dulled and faded at once.
Chemical damage from bleach and solvents, and the removal of heat tint from stainless steel, are not covered: no reliable source was located for them.
No entry gives a rate or a lifetime. How fast a colour fails depends on the product and the exposure.