UV Light and Its Effect on Wood
An important topic for restoration and repair work.

It is virtually impossible to get new wood to match old wood because nearly all species change in color, contrast, and/or brightness when exposed to any type of UV light. This includes natural light from the sun (both direct and indirect) and artificial light such as that which comes from fluorescent light bulbs. Some species like cherry will darken when exposed to UV light. Other species such as teak and walnut develop a very warm amber tone.

Though the color change begins immediately after the log is cut into lumber or veneer, the amount of time it takes for a full color transition depends on many factors including species, finish type, and the level of exposure to the UV source.

In some cases, a stain or wood dye can be used to make a lighter new wood look more like a darker old wood. This is often done with cherry. However, if the new wood is stained to match the old wood, then it is likely that the new wood will not match several months later when it has been exposed to UV light. At that point, it will often be much darker than anticipated.

With the exception of bleaching (which is not recommended), there is no way to make a darker wood appear brighter than a lighter, older wood. Additionally, it is only UV light that can make a wood like teak develop the amber tone.

More Information
The following links further explain how UV light effects teak.
www.mcilvain.com/news/teak-color-streaks
www.mcilvain.com/news/teak-decking-color-changes