UV Light, Timber, and Colour Change: What's Actually Happening to Your Shelves
If you own a Like Butter piece for long enough, you will notice it changing. A warm yellowing in the Hoop Pine. A deepening of tone in the Blackbutt. A lighter patch where a speaker used to sit on your KittaParts. A darker stripe where the sun hits the top of your Clip Crates every afternoon.
This is not a defect. It is timber behaving like timber. Here is what is actually going on, and what you can and cannot do about it.
The science bit (kept short)
Timber is made up of several compounds, the most relevant here being lignin: the natural polymer that binds wood fibres together and gives timber its colour and structure. Lignin is highly sensitive to UV light.
When UV radiation hits the surface of timber, it breaks down lignin through a process called photodegradation. The broken-down lignin produces chromophoric groups (chemical structures that absorb and reflect light differently), which is what causes the colour shift you see. In light-coloured softwoods like Hoop Pine, this typically manifests as yellowing and warming. In darker hardwoods like Blackbutt, the tone tends to deepen and richen.
Critically, this is a surface phenomenon. It happens in the outermost fraction of a millimetre of the timber. It does not compromise structural integrity. Your shelves are not weakening. They are patinating.
The rate of change is highest early in the timber's life and slows over time. The first year is when you will notice the most movement. After that, the timber reaches a more stable equilibrium.
Why Australia makes this more pronounced
Australia has some of the highest UV radiation levels in the world. The UV Index regularly hits extreme levels (11+) in summer across most of the country, and remains a year-round concern. UV is high even on cool or overcast days.
More relevantly for indoor furniture: standard window glass blocks most UVB radiation but transmits up to 75% of UVA. UVA is the longer-wavelength radiation primarily responsible for colour change in timber and fading in fabrics and flooring. Being inside does not mean being protected. A north-facing room with a large window and afternoon sun is a genuinely high-UV environment for your furniture.
If you have got shelves in a room like that, faster and more uneven colour change is the expected outcome, not an anomaly.
What our clear coat does (and what it does not)
We finish all sealed Like Butter furniture — KittaParts, The Shelves, Clip Crates, ThreadBoards — in a water-based clear coat containing UV absorbers. These work by absorbing UV radiation before it can reach the lignin in the timber surface, essentially acting as sunscreen for the wood.
This meaningfully slows the rate of colour change. It does not stop it.
We use a water-based finish deliberately. Oil and solvent-based finishes can themselves amber significantly over time, adding their own yellow on top of the timber's natural shift. Water-based finishes stay clearer for longer, which means the colour you see is the timber's own character, not the coating's contribution.
The Sherwin-Williams clear coat we use is specified for interior furniture and provides good UV stability for an indoor application. It is not an exterior-grade coating, and it is not designed to make timber colour-stable in direct sunlight indefinitely. Nothing does that.
The tan line problem
The most common complaint we hear about UV colour change is uneven toning, specifically a lighter patch where an object has been sitting on the shelf.
This is exactly what you would expect. The timber beneath the object was shielded while the surrounding area continued to shift. The result is a colour difference at the object's footprint: the furniture equivalent of a tan line.
The fix is time and even exposure. Move the object, let the lighter area catch up. In most cases the difference reduces to imperceptible within a few weeks to a few months depending on the room's UV exposure. The lighter area is not damaged. It is just behind.
What you can actually do
Slow the change:
- Keep shelves out of direct beam sunlight where colour consistency matters to you
- UV-filtering window film on high-sun windows is genuinely effective. Quality films block 99%+ of UV, including the UVA that gets through standard glass
- Rotate objects periodically so exposure is even across the surface
Work with the change:
- Accept that patination is part of owning real timber. A Like Butter piece that is five years old looks different from one that is five weeks old, and most people find the aged version warmer and more characterful
- Hoop Pine in particular develops a honey tone over time that many owners prefer to the raw original
If you want to re-finish:
- A light sand with 180-grit and a fresh coat of water-based clear coat in the original sheen level will even out surface variation and provide a renewed UV barrier
- Message Jem before you do this. He can advise on the right product and process for your specific finish
The bottom line
Timber furniture changes colour. It always has. The question is not whether it happens. It is whether you understand why, and whether you think of it as decay or as character.
We think it is character. We make things to last decades, not to look perfect in a product photograph forever. A Like Butter piece that has been in a sunny Melbourne living room for ten years tells you something. It has been there. It has done the job. It is yours.
If you have got a specific situation (a tan line that is bothering you, a patch that looks wrong, a finish question), Message Jem. It is his personal number. He will give you a straight answer.
