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How weather and wood stain can affect the wood in windows

stained wood window frames in skylight

Milky wood stain

Most winters we have a case of newly installed joinery products with an external wood stain going milky. This is particularly likely during exceptionally wet weather periods, which is why it tends to occur on winter installations. Firstly, if this happens on your products, then it is nothing to be concerned about. The cloudiness/milkyness of the coating will dissipate completely within the first 3 months of install to leave a perfect finish.

Why does this occur? Basically, water based coating systems are microporous in nature. This means that they allow small quantities of moisture through the coating in both directions to reach a natural equilibrium with the environment. This has a number of effects that lead to longer lasting coatings which do not crack. However, microporous coatings will typically require 6-8 weeks from application of final top coat to completely cure. This means that they can become slightly overwhelmed if exposed to periods of excessive wet weather immediately after install, causing them to take on extra moisture between the layers of coating and gives the milky effect. You will notice that this will occur more on the horizontal surfaces where water is held for longer by the surface.

As the weather improves, the coating will cure further and the moisture will be released back into the environment. This will lead to the milkyness subsiding and the stain being restored to the expected colour and finish. The effect is well known to the coatings industry and is not a cause for concern. Once the coating is fully cured, the stain going milky effect will not return.

If you experience extended periods of milkyness, or the milkyness occurs after the first 6 months of service, then please call us and we will do further investigation. Obviously all of our coatings are fully covered under our comprehensive guarantee.

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