How weather and wood stain can affect the wood in windows
Milky wood stain
It’s not uncommon during a wet winter for newly installed timber windows to develop a slightly milky or cloudy appearance in the wood stain. If this happens, don’t worry—it’s a temporary effect and nothing to be concerned about. The appearance will clear naturally within the first three months, leaving a smooth, flawless finish.
Why Does the Stain Turn Milky?
This effect is caused by the nature of water-based coating systems. These coatings are microporous, meaning they allow small amounts of moisture to pass through the surface. This helps the timber maintain a healthy balance with its environment and gives the coating added flexibility and durability. Microporous finishes are far less likely to crack or flake over time.
However, these coatings need 6 to 8 weeks to fully cure after the final topcoat is applied. If your windows are installed during periods of heavy or prolonged rainfall—especially in winter—excess moisture can get trapped between the layers of the coating before it has finished curing. This is what causes the temporary milky effect.
The issue is most commonly seen on horizontal surfaces, where water tends to collect and sit for longer.
What Happens Next?
As the weather dries out and the coating continues to cure, the trapped moisture is released back into the air. The cloudy appearance fades and the wood stain returns to its original colour and finish.
This is a well-known and well-documented characteristic of microporous coatings. Once fully cured, the effect will not come back.
When to Get in Touch
If the milky appearance lasts longer than three months, or appears after the product has been installed for more than six months, please let us know. Our team will be happy to investigate.
All our finishes are fully covered under our comprehensive guarantee, so you’re always protected.