Bruce Hamilton replies: The first step in attempting to preserve the natural colors of various woods is to reduce their exposure to sun light. Unfortunately this is not always possible or practical. The next step is to use finishes that contain ultra light inhibitors which are designated by the initials UV. I would expect to find finishes with this additive in stores that supply marine varnishes. These varnishes are also known as long oil varnish because they do not dry as hard as regular varnishes so they can expand and contract with changes of temperature and exposure to water without cracking. Most of the varnishes have a natural occurring yellow tint. You need to read the labels carefully to verify that the product contains UV inhibitors or refer to the material safety data sheet on the internet. UV inhibitors additives are expensive so you are most likely to find these with the more expensive varnishes. The West System Epoxies have UV inhibitors and available from Rocklers. Epifane varnishes have a good reputation for outdoor exposure. See the Fine Woodworking article post in #112277 from April 2009 and checkout YouTube. There is a new book, Wood Data by Eric Meier, that addresses the loss of color in exotic woods. I haven’t read it yet but if anyone in the Guild has a review would very interesting.
Richard Oedel replies: As one old salt told me about color in wood, “If you want the wood (he was talking about padauk) to stay red, then stain it red.” I’ve found that very few woods stay their natural color when exposed to light and oxidizers. While some finishes that say they have a UV inhibitor in them, they will just delay the color change. It is short lived. If you really want to keep the color for the lifetime of the piece, match the color and stain it with a lightproof stain.