A non-yellowing finish
Russ Fairfield
>Randy Hodge asked the question about a "non-yellowing" finish over on the WOW site. I am repeating it here because it might be of general interest.
Keeping the natural color of the wood is something that I am often asked about
There is no simple answer.
There are three kinds of "yellowing", that which is natural to the wood with age and exposure to sunlight and air, that imparted to the wood by the finish, and the yellowing of the finish itself.
Add to all of this that different woods react to natural coloring and the color imparted by the finish to different degrees. The word "Yellowing" is an all inclusive description of a color change that can range from a very light almost imperceptable yellow through a dark amber to dark brown and almost black.
The thing to remember through all of this is that nothing is permanent. Every wood and everything we can put on it will deteriorate with age and head towards a darker color. We can slow that process down but there is nothing we can do to prevent it.
First, to correct the statement about Mineral Oil in your question. Mineral Oil doesn't dry, it just soaks further into the wood until it all but disappears and has the appearance of having "dried". Mineral Oil does not change color with age. What you are seeing is the wood changing color, and the presence of the Mineral Oil can hasten that process in some species and wood conditions.
Contrary to what we want to believe, there is nothing that will prevent the wood from changing color with age. We can slow it down to where it will appear in the short term that we have done something to preserve the natural color. But, the UV blockers will deteriorate with age, and the wood's natural march towards a darker color will continue. Just like the Armor-All we put on the vinyl trim of our car, and UV blocker will deteriorate with time, and require removal and replacement if we want to keep its UV blocking properties.
The least amount of color change is to leave the wood alone, with nothing on it other than a polished surface, and keeping it out of direct or filtered sunlight. The only color change will be that from natural aging and exposure to light and air. The disadvantage is that that there is nothing to protect the wood from airborne chemicals, molds, and moisture.
Some degree of color added to the wood is usually desireable. Without color, there is no accenting of the grain. That accenting is the result of the different amount of the finish that is absorbed into the end and flat grain areas, and the resulting differences in color.
Anything we put on the wood, other than a dead flat finish, will impart a "wet look" to the wood. Even when there is no color change, we see this as adding brightness to the wood. A warning - don't confuse "brightness" with "color change". They are different.
Wax will not add color to the wood, but it will add brightness. If you want to keep the wood as it is for the longest time, use a good quality wax. The only problem is that it isn't a durable finish and it will require a periodic renewal or replacement.
A lacquer, such as Deft, adds considerable brightness and that alone will accent the natural grain patterns of the wood. Wet the wood with water if you want a preview of what a lacquer will do to it.
However, the nitrocellulose lacquers will turn a darker color as they age. Deft shows the least color change of any, and it is formulated for a convenient brush application. A CAB-Acrylic lacquer would be a better choice, because it is water white in the can and will stay that way for our lifetime; but it would require spraying because it doesn't brush very well, even with retarding thinners.
Waterborne finishes such as the acrylics or the lacquers are also very color neutral. However this color neutrality does nothing to accent the grain, gives no brightness or "wet" look to the wood, and most of them have not solved the bluish color cast that they impart to light reflected from the surface. Many of them have added oils in order to correct the lack of brightness and to add some accent to the wood. However, when that is done they will still turn dark with age like everything else we can put on a piece of wood, only more slowly.
Oil finishes have the advantage of making all of the color change in the wood in one shot at the time of their application. There is no waiting. This is usually desireably on a wood like Maple where we want to accent the grain and impart that golden amber color. After that first color change, the wood will not change much more with age. However, what happens to the finish itself with age will depend on the oil and the varnish resins (if any) that are used. Tung Oil does not turn as dark as fast as Linseed Oil, and the fortified Soybean Oil that is used in so many of the commercial finishes will turn the darkest of all. For varnishes, the phenolic resins will change color the least, and the polyurethanes will turn the darkest orange of anything you can put on the wood. The reason we like polyurethane resins is their hardness and durability, but we wouldn't choose one of them if we were wanting the wood to stay its natural color for the longest time. Waterlox is an excellent oil finish because it has both the Tung Oil and the Phenolic resins, but we have to pay the price for those ingredients.
Add to all of this that every species of wood, and often just different pieces of wood of the same species, will react to any of these finishes differently from all others; and that there is no one finish that will do everything that we want. So we look at the compromises, make our choice, and hope for the best. Only time and the passing of years will tell us if it was the right one; and that is called "experience".
