Short answer
Wood's colour comes from lignin and from extractives — tannins, phenolics and resins — that differ by species and between sapwood and heartwood. Light, especially ultraviolet and violet, breaks down lignin and alters extractives at the surface, so indoors pale woods such as pine and spruce yellow and brown, while some dark woods fade first; outdoors, the degraded lignin washes away and every species turns silver-grey. The finish, the light the piece gets and how deep the change goes all decide how much you see.
Relative to other materials in this section, not a measurement of a particular product.
| Process | What you see | Driven by | Slowing it |
|---|---|---|---|
| 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 |
| Weathering (outdoors) | Silver-grey surface | Degraded lignin washed out, leaving cellulose; mould adds dark grey | Pigmented stains or paint; clear finishes fail quickly outdoors |
| Iron–tannin staining | Blue-black marks around fixings | Iron reacting with tannins in damp wood | Stainless fixings; oxalic acid treatment |
Colours that work with wood (solid timber and veneer) in a room
Cellulose, the bulk of wood, is nearly colourless. Lignin, the polymer that binds the fibres, absorbs strongly in the ultraviolet and gives wood its basic pale yellow-brown. Species colour mostly comes from extractives deposited as sapwood turns to heartwood: tannins in oak and chestnut, dark phenolic compounds in walnut and rosewood, reddish compounds in cherry and mahogany, resins in pines. That is why the heartwood of most species is darker than the sapwood around it, and why boards cut from the edge of a log can be two-toned. Extractives also react with metals and moisture — iron fixings in damp oak produce blue-black iron–tannin stains, the same chemistry as iron-gall ink.
Lignin absorbs ultraviolet across roughly 250–400 nm, and violet visible light also contributes to discolouration. The absorbed energy forms phenoxy radicals that react with oxygen to create quinone-type structures, which are yellow to brown. Pale woods therefore yellow and warm — the familiar ambering of pine and spruce, the deepening of maple and birch — while some darker woods first fade as their coloured extractives are bleached, then yellow or brown. A rug or picture left in one place leaves a paler, fresher-looking 'shadow' when moved. The change is fastest in the first months and slows, and it is shallow: most of the action is in the top fraction of a millimetre, so a light sanding exposes wood close to its original colour.
Any clear oil, lacquer or varnish darkens and saturates wood because it fills the fibre surfaces and suppresses scattering — the same effect as wetting. Oil-based finishes add their own amber, which deepens as they age; water-borne acrylics and polyurethanes stay paler. Most clear finishes are themselves transparent to much of the light that discolours wood, so the wood under them keeps changing. In a laboratory ageing study, lacquered spruce darkened and shifted towards red and yellow by ΔE of roughly 10 to 19 under several solvent-borne polyurethanes, while lacquered oak changed less; a lacquer containing a UV absorber performed better. Outdoors, most clear coatings fail within about two years in a temperate climate, because the degraded wood beneath loses its grip on the film.
In the weather, light degrades the lignin at the surface and rain washes the fragments out along with water-soluble extractives. What remains is a loose layer of cellulose fibres, which is pale silver-grey; mould growing on it adds dark grey. Whatever the species, the end state looks broadly similar, which is why cedar cladding, oak benches and pine fences all converge on grey. The weathered layer erodes slowly — of the order of a few millimetres per century — so the colour change is thin even though it is dramatic. To keep a timber colour outdoors, the surface needs light-blocking pigment: pigmented stains and paints last far longer than clear finishes because the pigment, not the wood, takes the light.
Veneer is wood sliced or peeled thin and glued to a stable core, so the colour chemistry above applies unchanged, but three things differ. First, cut: rotary-peeled veneer shows a wild, wide grain; quarter-sliced veneer shows straight stripes and, in oak, the silvery ray fleck; crown-cut shows cathedral figure. Each reflects light differently, so the same species can look lighter or darker by cut. Second, figure and chatoyance — the shimmer across ribbon-striped sapele or figured maple — change with viewing angle, so leaves laid in different orientations look like different colours; matching (book, slip, random) controls this. Third, veneer is thin, so sanding through it to repair colour change is risky, and light reaches the glue line sooner on very thin veneers.
| Substrate and finish | ΔE*ab after ageing | Direction of change |
|---|---|---|
| Spruce, several solvent-borne PUR lacquers | ≈ 10–19 | Darker, redder, yellower |
| Spruce, PUR lacquer with UV absorber | Lower than the other PURs | Same direction, smaller |
| Oak, same solvent-borne lacquers | ≈ 4–11 | Smaller shifts in L*, a*, b* |
| Spruce, water-borne lacquers | ≈ 3–11 | Depends on the system |
Why: Photo-oxidation of lignin, often compounded by an ambering oil-based finish.
Fix: Accept it, or sand back and refinish with a water-borne finish with UV absorber; a white-tinted finish offsets warmth.
Why: The covered area received less light and changed less.
Fix: Leave the floor evenly exposed for some months; the contrast usually fades as the patch catches up.
Why: Clear oil offers little protection against light and washes out.
Fix: Use a pigmented stain on a maintenance cycle, or plan for the grey.
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
Lignin absorbs ultraviolet light across roughly 250–400 nm and visible light up to the violet also contributes to wood discolouration; photodegradation forms quinoid structures responsible for yellowing.
Source: Enhancing Weathering Resistance of Wood — A Review (Polymers 13, 1980); Effects of UV radiation on natural and synthetic materials (Photochem. Photobiol. Sci.)
FactStrong evidence
In weathering, light-coloured woods usually turn yellow or brown and darker woods may first fade; eventually all species turn grey as photodegraded lignin is leached out, leaving a cellulose-rich surface.
Source: Enhancing Weathering Resistance of Wood — A Review (Polymers 13, 1980); Wood Handbook (FPL-GTR-282), Chapter 16: Finishing Wood
FactModerate evidence
Under accelerated ageing, spruce finished with several solvent-borne polyurethane lacquers showed colour changes of about ΔE 10–19, darkening and shifting towards red and yellow, while oak with the same lacquers changed by about ΔE 4–11.
Method: Accelerated UV ageing of lacquered samples, CIELAB colour measurement before and after.
Caveat: One laboratory study with accelerated ageing; real-room rates depend on light dose and spectrum.
FactStrong evidence
Most clear coatings on wood fail after about two years outdoors in temperate climates, and weathered wood surfaces erode at about 3 mm per century for hardwoods and 6 mm per century for softwoods.
Caveat: Averages; exposure, climate and coating type change them substantially.
Source: Enhancing Weathering Resistance of Wood — A Review (Polymers 13, 1980)
FactStrong evidence
Iron reacting with tannins in damp wood forms blue-black iron stain, which oxalic acid can remove.
Source: Wood Handbook (FPL-GTR-282), Chapter 16: Finishing Wood
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.