When it comes to woodworking and finishing projects, there’s often a debate about whether or not the finish used will alter the wood’s natural color. Many individuals believe that certain finishes, such as varnishes, add a yellow or amber hue to the wood, while others prefer to see the wood’s natural color unaltered by the finish. In this article, we’ll explore why yellowing occurs and discuss various types of finishes that may or may not change the wood’s appearance.
The primary goal of any finish is to protect the wood, but it’s also undeniable that the application of the first coat of finish reveals the natural beauty of the wood. Depending on the type of finish used, a piece of maple that appears nearly white when bare can become yellow or even brown. While some people appreciate this effect for its rich, traditional appearance, others may see it as old-fashioned and prefer to see the wood’s natural, unaltered color.
In most woodworking workshops, you’ll likely find four types of finishes: water-based polyurethane, oil-based polyurethane, alcohol-based shellac, and natural penetrating oils like tung oil or boiled linseed oil. Each of these finishes has its unique characteristics that may make them suitable or unsuitable for your project, but our focus will be on how they affect the wood’s color.
Natural penetrating oils, such as tung oil and boiled linseed oil, are known to change the wood’s color. You can see this change just by looking at how yellow the oil appears prior to application. These oils will yellow and darken the wood more than other common finishes, with linseed oil being particularly prone to darkening over time as it breaks down.
Oil-based polyurethane, including Danish oil and tung oil blends that contain polyurethane, will also yellow the wood, although to a lesser extent. This yellowing occurs due to the manufacturing process that utilizes aromatic isocyanates. Over time, exposure to UV rays will break down these compounds, causing the finish to become even more yellow or golden.
Water-based polyurethane, on the other hand, is often touted as being more clear because it lacks oil as its solvent. Depending on the quality of the water-based poly, it may contain elephantic isocyanates, which are resistant to UV light and do not produce the same yellowing byproducts as oil-based poly. While water-based polyurethane may not remain crystal clear forever, any yellowing that occurs over time will be more subtle compared to oil-based poly.
An example of a well-known water-based polyurethane finish is Minwax Polycrylic. This proprietary product is similar to traditional polyurethane finishes but has some key differences in chemical makeup. Polycrylic does not yellow at all, even over time. However, it may produce a milky appearance that some individuals argue is worse than yellowing.
Shellac, which is the most common alcohol-based finish found in small woodworking shops, is made from secretions of a beetle dissolved in alcohol. The color of shellac can vary depending on the beetle’s diet, resulting in shades ranging from orange-brown to nearly clear. While no shellac is perfectly clear, it does not darken over time like other finishes. However, it will change the tone of the wood to some extent.
Lacquers, although less common in small woodworking shops, should also be mentioned. Generally, lacquers do yellow over time, some more significantly than others.
Considering all of these factors, it becomes clear that no finish will preserve the wood’s exact, bare appearance. All finishes will have some effect on the wood’s color and overall appearance. Water-based polyurethane tends to have the least yellowing effect when applied, with minimal changes over time. However, it may give the wood a plasticky appearance and potentially cloud the grain, which can be compared to floor wax.
While there are advancements being made in water-based finishes, it’s important to note that not all brands are created equal. It’s recommended to try higher quality water-based polys on some test pieces to see how they look and perform.
Shellac comes closest to preserving the wood’s natural color, especially if you opt for the lightest, highest quality flakes and dissolve them yourself. Pre-mixed shellac is generally blonde at best and does not darken significantly over time. However, there may be some debate about this point.
Oil-based polyurethane is known for its durability and is a popular choice in small woodworking shops. However, it tends to give wood a more golden appearance, especially when used on light-colored wood. Over time, exposure to light can cause the finish to become even more yellow.
For those looking for a middle ground between polyurethane and natural oils, natural oil blends like Danish oil, tung oil finish, or water locks may be suitable options. These blends often claim to preserve the wood’s natural appearance, but the yellowing effect can vary from brand to brand. The inclusion of natural oils in these finishes contributes to the yellow tint they produce, but the only way to know the extent of their impact on your project is to test a sample.
Pure oil finishes, such as tung oil and boiled linseed oil, are known to yellow the wood even before application. However, some woodworkers argue that this change in color does not necessarily detract from the wood’s beauty. These finishes preserve the depth and natural beauty of the wood grain, which many consider the most important factor. Additionally, it’s important to note that wood itself naturally changes color over time, regardless of the finish applied.
In conclusion, finding the perfect finish that preserves the wood’s appearance exactly as it appears in its bare state is nearly impossible. All finishes will have some effect on the wood’s color and overall appearance. Water-based polyurethane and shellac are often regarded as the options that best preserve the wood’s natural color, although they each have their own pros and cons. Oil-based polyurethane and natural oil blends may change the wood’s color to varying degrees, while pure oil finishes will noticeably yellow the wood but maintain the depth and beauty of the grain.
Ultimately, the right finish for your project will depend on your personal preferences and the desired aesthetic outcome. It may be beneficial to experiment with different finishes on test pieces to find the perfect balance between preserving the wood’s natural color and achieving the desired finish.
Now that you have a better understanding of wood finishes and their impact on the wood’s appearance, you can confidently choose the finish that best suits your project and showcases the beauty of the wood grain. Happy woodworking!
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