Technical Details

At Monarch Plank we believe in the value of educating our customers. This page is our effort to give you a window into our world. We invite both our wholesale customers and end-users of our flooring to share in our delight for the finer points of wood coloring, coating, and sourcing. We are confident that this information will help you make better decisions when selecting or helping your customers select our flooring products. We hope that you'll take the time to read this entire page, but if there is a subject that interests you most, use the links to the right to skip ahead.


NOTE: throughout this text, when we refer to ‘oil finishes,’ we are referring to finishes that are made with natural oils such as soy and linseed. These are not to be confused with ‘oil-based’ or ‘oil-modified’ polyurethanes, which are a completely different family of finishes, made primarily of petroleum products.

Urethane floor finishes are very durable and are currently the most popular choice in the U.S., but at Monarch Plank we believe that natural oil finishes would be more popular if they were better understood. In Europe, where oil finishes have a long tradition, they make up roughly one third of the residential flooring market and one half of the commercial market.

Oil and urethane finishes reflect two completely different approaches – oils work by fortifying and sealing the wood fibers, while urethane works by walling them off. With an oiled floor, you are walking on the natural wood surface. With a urethane floor, you are walking on a man-made barrier. Consider this analogy:

Oil is to urethane as skin is to a raincoat.

An oil finish penetrates into the wood and hardens to become an integral part of the floor, just as skin is an integral part of the body. A urethane finish is a protective layer that covers the floor, like a raincoat.
Consumers often ask which type of finish is more durable, urethane or oil, but there is no simple answer to that question.


There is a common perception that oil finishes are more difficult to maintain than urethane, and that is true in the short term, because they require the regular use of special soaps and every few years need to be re-oiled. But if you consider the total long-term cost and hassle of maintaining the floor, oil finishes may actually require less maintenance, especially for someone who plans to stay in the same home for many years.

Like a raincoat, a urethane finish provides excellent protection, but its appearance and performance are never again as good as on the day it was installed. Gradually the floor gets more and more scratched up until you eventually have to sand and recoat it. Urethane finishes can’t be patched or touched up. Repairing scratches requires replacing individual boards, or recoating the entire floor - throwing away that old raincoat.

By contrast, an oiled floor that gets damaged in a particular location can usually be treated locally and blended with the rest of the floor. And, the entire floor can be refreshed fairly easily by nourishing the wood with more oil, which will remove most signs of wear and tear without sanding. Like skin, an oiled floor that is well cared for may last a lifetime.

A urethane-coated floor will, on average, need to be sanded and refinished every 10-12 years. A properly maintained oil finish will require re-oiling every 3-5 years. So, the maintenance of oiled wood floors is more frequent, but it is far less disruptive because it generally requires no sanding. To be sure, some of the patina and wear patterns in an oiled floor will still be visible after re-oiling, but for consumers looking for an antique or weathered look, this only adds to the floor’s appeal.

It’s important to mention that the ease of doing a localized repair on an oil finish depends on the complexity of the original color and how worn the floor becomes before the problem is addressed. Doing a repair on a color that was created with multiple layers of treatments requires more skill than most homeowners possess. Also, if someone doesn’t maintain an oiled floor properly and allows the oil to wear down to the point where the wood is no longer protected, the wood may discolor and can only be fixed by sanding and refinishing. Oiled floors therefore may not be the best choice for people who are likely to neglect their wood.

A few additional factors to consider:

- The cost of the products used to clean and maintain an oiled floor is slightly higher than the products used to clean urethane finishes.

- With oil finishes, it’s critical that you maintain them with the right products, which are specific to the type of oil that was used on your floor.

- Oil soaps and finishes tend to have mild odors, whereas cleaning products for urethane finishes are usually odorless.



As with most anything else, picking a floor finish generally involves making trade-offs. Let’s look at some of the advantages and disadvantages of the different finishes most commonly used at today’s wood flooring factories.


UV-cured urethane (or simply ‘UV urethane’) is the most common type of finish for prefinished wood flooring. The finish is applied to the wood at the factory and then hardened via a chemical reaction triggered by ultra violet (UV) light. Like other urethane finishes, UV urethanes protect the wood by creating an artificial barrier between the wood and the traffic above.

- Hard, durable, and stain resistant
- Barrier above wood helps protect against physical damage
- Requires no topcoat after installation

- Finish build looks like plastic - artificial
- Scratches generally show as white lines - highly visible
- Refreshing requires sanding/abrading
- Can’t be feathered - repairs require board replacements or recoat of entire floor


Aluminum oxide is one of several types of particles that are sometimes added to UV urethane finishes to make them more abrasion-resistant. Other additives that are commonly used include silica oxide (‘ceramic’ finishes) and titanium oxide. UV urethane finishes are sometimes mistakenly referred to as ‘aluminum oxide’ finishes. While many UV urethane finishes do contain aluminum oxide, many don’t.

When aluminum oxide and ceramic finishes were first introduced to the marketplace, they were often added to the topcoat to make the floor more scratch resistant. Over time, many manufacturers abandoned this strategy because they found that as the coating wore down, the additive particles would create micro-scratches in the finish that would give it a cloudy look. The abrasion resistance of the topcoat also made it more difficult to screen in preparation for a refresher coat. Now, most manufacturers who use aluminum oxide and other additives apply them in the sealer (base coat) to serve as a last defense against finish wear-through. So, the idea that additives like aluminum oxide make a finish more scratch resistant is usually not correct. They simply make it more wear-through resistant.

The enhanced wear-through resistance achieved by these additives is the main reason that manufacturers are now able to offer very long finish warranties of 35 and even 50 years. These warranties give the impression to consumers that the finish will perform and look better than other finishes. But to most consumers, the scratches are what bother them most, and the manufacturer with the long warranty could just be adding large amounts of aluminum oxide in the base coat of a low quality finish. Such a finish will get scratched up and need a recoat in five years, and the scratches aren’t covered under the product’s meaningless 50 year warranty.

Some manufacturers, particularly in Europe, prefer to leave additives like aluminum oxide out of their finishes for two reasons. First, they affect clarity, creating a hazy look, and second, they make it more difficult to refresh the finish with a topcoat. At Monarch Plank, we agree with the Europeans. We believe that the added wear-through resistance provided by these additives isn’t worth sacrificing beauty and repairability, since most people refinish their floors due to scratches long before the finish comes close to wearing through. We choose instead to use quality top-coats that give maximum scratch resistance and total finish clarity.

One common myth about UV urethane finishes, and urethanes in general, is that they are water-proof and will not be stained by liquids left on the floor. In fact, if you look at urethane finishes under a microscope, you can see thousands of tiny pores. Water vapor can slowly pass through these pores, and, given enough time, chemicals left on the surface of the floor (including coffee, wine, pet urine, etc.) will make their way down through these pores and discolor both the finish and the wood beneath. It is true that urethanes are generally more stain resistant than oil finishes, but it’s not true that they are immune to such damage.


Sometimes referred to as ‘traditional’ oils or ‘natural’ oils, penetrating oil finishes generally contain a natural oil base, such as linseed, that is mixed with solvents to accelerate drying. Tung oil is a well-known example of a penetrating oil finish. Penetrating oils absorb into the wood and usually require the application of at least two coats. Penetrating oil finishes are referred to as ‘oxidative’ oils, because they dry by exposure to the air, as opposed to UV-cured finishes, which only harden with exposure to UV light.

- Natural look and feel - soaks into the fibers rather than covering them with plastic
- Easier to repair – new oil can be feathered into the surrounding finish
- Can be refreshed without sanding

- Usually requires a topcoat of oil after installation
- Less stain resistant than urethane
- Wood is more exposed to physical damage
- Requires regular maintenance with proper cleaning products


Hardwax oils are another type of ‘oxidative’ (air-dried) oil. Hardwax oil finishes are like penetrating oil finishes in that they contain some natural oil such as linseed or soy that is mixed with a solvent to accelerate drying. Hardwax oils are different from penetrating oils, however, in that they also contain wax, usually a mixture of paraffin with carnauba and/or beeswax. When hardwax oils are applied, the oil soaks into the wood and separates from the wax, which is left at the surface. This wax layer is then buffed in to give the wood an attractive, silky luster. The wax also helps to seal the floor.

Most hardwax oils on the market require the application of at least two coats, but there are some ‘single-coat’ hardwax oils that make use of isocyanate hardeners to bond quickly to the wood fiber and create a seal with just one thin application. These single-coat hardwax oil finishes have unique characteristics that require that they be maintained with different types of soaps and cleaners than most oil finishes.

The advantages and disadvantages of hardwax oil finishes are more or less the same as penetrating oil finishes:

- Natural look and feel - soaks into the fibers rather than covering them with plastic
- Easier to repair – new hardwax oil can be buffed into the surrounding finish
- Can be refreshed without sanding

- May require a topcoat of oil after installation
- Less stain resistant than urethane
- Wood is more exposed to physical damage
- Requires regular maintenance with proper cleaning products


Like other oil finishes, UV oils are intended to protect the wood from within by sealing the fibers, rather than creating a barrier between the wood and the traffic above, as urethanes do. However, almost all UV oils contain some percentage of acrylic, the main component in urethane finishes, which is why UV oils are often viewed as hybrids between urethanes and oils. The higher the acrylic content of a UV oil, the more it will perform like a urethane, with all of the associated pros and cons. Higher acrylic content lends better stain resistance and protects the wood fibers better from physical damage, but also creates more of the plastic looking build above the wood, is more challenging to repair, and may show white in the scratches like a urethane. Like UV urethanes, UV oils are cured at the factory via a chemical reaction triggered by UV light.

- Can be nourished and refreshed without sanding, like other oils
- Natural look and feel
- Requires no topcoat after installation
- Better stain resistance than penetrating or hardwax oils
- Better initial durability than penetrating or hardwax oils – longer before first re-oiling

- Can be more difficult to blend/repair than other oils
- Less stain resistant than urethane
- Requires regular maintenance with proper cleaning products


At Monarch Plank, we believe that each of these types of finishes has its advantages, and that the right choice depends on personal preferences. Some people want their wood floor to look as natural as possible, look forward to the floor taking on a patina from daily use, and like the idea that they can repair or refresh their floor with a little bit of work on a Saturday afternoon. For them, a Penetrating Oil or Hardwax Oil finish might be a good choice. Others might enjoy the natural look and feel of an oil finish, but prefer a little bit more durability, stain resistance, and easier initial maintenance. For them, a UV Oil may be a better choice.  Still others want a floor they can install and forget about, requiring as little maintenance as possible until it’s time to replace or refinish the floor completely. Or the floor might be going into a location where the occupants can’t be trusted to use the specialty care products required for oil finishes. In these cases, UV Urethane is probably the better choice.

We have manufactured and sold floors with all three of these families of finishes, but our current product line emphasizes UV Oil and UV Urethane options. With our ultra low-gloss, low build urethanes and UV Oils, we can provide the look and feel of the most natural finish without sacrificing stain resistance and durability. Penetrating Oil and Hardwax Oil finishes definitely have their place, but we have found that the amount of education and care that those finishes require can be surprising to many consumers.


Monarch Plank's oiled floors do not require top-coating after installation, which is a requirement with many other oiled wood floors currently on the market. This is a huge added cost and inconvenience that is sometimes not mentioned at the point of sale. At Monarch Plank, we put that final topcoat on for you at the factory.

The fact that we apply a topcoat of clear or white oil above the colored oils used to generate some of our colors has another important benefit. It allows periodic maintenance and re-oiling without the need to find a special colored oil to match the original color that we applied at the factory.



UV-cured urethane finishes are sometimes mistakenly referred to as ‘water-based’ because they don’t contain solvents, but they are actually not water-based. They are 100% solids, meaning they have no solvent OR water content. They dry purely by exposure to UV lights, and once that reaction is complete there is no further off-gassing. They are also easy to clean with benign, odorless cleaning agents that leave no residue on the floor. These characteristics make UV-cured urethanes a good alternative for people looking for a floor and cleaning system that will not introduce any odor or off-gassing into the home.


The natural oils that are the base ingredients in penetrating oils will not dry quickly enough for practical use unless solvents are added. The types of solvents used by the penetrating oil manufacturers vary, and usually depend on which natural oil is chosen as the base ingredient. Penetrating oil manufacturers usually try to use relatively benign solvents like white alcohol, but consumers concerned about exposure to these solvents should check the individual product information.

Generally, manufacturers who use penetrating oil finishes on their prefinished floors will allow the finish to cure for a period before packaging, but that curing process often isn’t 100% complete at the time of packaging. Once packaged, the curing process gets put on hold while the product is protected from air circulation. For that reason, consumers may detect a slight odor when a floor finished with penetrating oil is first installed.


In order to suspend the wax ingredients in liquid form, hardwax oils contain very high solvent content. Their sale and application are not permitted in some regulatory areas.

Some of the ‘single-coat’ hardwax oils on the market are advertised as being zero-VOC. However, it’s important to note that this technology relies on isocyanate as a hardener. Isocyanate is not classified in the U.S. as a VOC because it is not a smog-producing chemical, and manufacturers therefore aren’t required to include it in their VOC calculation. But in many other countries isocyanate IS classified as a VOC, and is considered harmful. Being ‘Zero-VOC’ in the U.S. does not necessarily mean being free of odors or harmful ingredients.

Similar to prefinished floors finished with penetrating oils, floors finished with hardwax oils may have a slight odor when they are first removed from the packaging, as the finish may still be going through the final stages of curing.


Like UV-cured urethanes, UV oils are dried completely in a UV oven at the factory and will not off-gas in the home during or after installation. However, the cleaning and maintenance products for UV oil are the same as those for other types of oil and may contain VOC’s or have a slight odor.



In recent years, wood flooring tastes have grown more and more sophisticated. Consumers and designers today often seek out the most natural-looking finishes possible, avoiding the traditional high-build, high-gloss floor finishes that once dominated the market. There has also been a trend away from color uniformity, as the painted look of the traditional stained floor has lost popularity in favor of floors that show some natural variation. Consumers seem to want colors that look as though they developed naturally, either as a creation of the forest or through natural aging and patina.

At Monarch Plank we have embraced this trend and employ several different techniques to achieve these natural looks. We use Fuming (aka Smoking), Carbonization, and Reactive Stain technologies. While traditional wood stains add color by painting pigments on to the wood, these techniques create color from within the wood by causing reactions in its natural ingredients. The results are spectacular, but it’s important for consumers to understand and embrace these natural variations before they finalize their floor selection.

One advantage of fuming, carbonization and reactive stains is that they don’t create the pronounced black lines in the wood grain that are left by traditional stains. All traditional stains employ pigments, and when applied, those pigments tend to accumulate very heavily in the open growth rings of the wood, causing the black lines. With these reactive processes, we can achieve dark colors without those unnatural looking lines. Many reactive stains actually create the reverse effect, lightening the open growth rings, for an effect similar to that created by weathering outdoors.


Fumed (aka ‘Smoked’) wood has been exposed to ammonia gas. The ammonia reacts with the natural tannins in the wood and brings out a darker color, usually a grayish-brown. Fuming was an accidental discovery, made in England after it was noticed that Oak boards stored in a stable had darkened from exposure to the ammonia fumes from horse urine.

European Oak is the preferred species for fuming/smoking because of its high tannin content. American White Oak is sometimes fumed/smoked, but it tends to react less intensely, has more variation, and sometimes takes on a greenish color.

Because the intensity of the reaction to the ammonia depends on the tannin content of the wood, each board reacts a little bit differently from the next. This creates color variation that can be more pronounced than if the wood were not treated or colored at all. In Europe, where fuming is a traditional technique that has been used for centuries, consumers are accustomed to this variation, but in the U.S., many people are unfamiliar with it and can be a bit surprised by how much variation is present in the floor.

For manufacturers who want to improve color consistency in a fumed/smoked floor, careful lumber sourcing can help to some degree. Oak from Western Europe, especially France and Germany, tends to have higher tannin content than Oak from Eastern Europe and the Russian Far East. Along the same longitude, wood from farther North will tend to have higher tannin content than wood from the South. When a floor has really extreme color variation, it may be that the manufacturer mixed material from far away regions. At Monarch Plank, we don’t do that. (For more on how and where we source our wood, see the ‘EUROPEAN OAK VS. RUSSIAN OAK’ section under ‘ALL ABOUT OAK.’)

However, no matter how carefully the lumber is sourced, variation is inevitable. Even within a relatively small forest area, tannin content can vary dramatically, and it varies quite a bit even within the same log, depending on which portion is used. (For more details on tannin variation, see the ‘TANNIN VARIATION’ section under ‘ALL ABOUT OAK.’)

Consumers looking for a floor with uniform color should generally be steered away from colors created with smoked/fumed wood. That said, Monarch Plank does offer smoked/fumed products that are color sorted for greater consistency. Ask your Monarch Plank Sales Representative or Monarch Plank Preferred Dealer about which fumed products have been sorted for consistency.


Carbonized wood has been heat-treated. The heat literally caramelizes the naturally occurring sugars in the wood, creating a rich caramel brown color. The color of carbonized wood is warmer than the color that results from fuming/smoking. Because the sugar content of individual boards can vary more dramatically than tannin content, carbonization tends to create even more color variation than fuming/smoking.

Though controlling the color in carbonized wood is challenging, we believe that these challenges are greatly outweighed by the beauty this process creates. The richness and natural look of carbonized Oak simply can’t be replicated with topical stain techniques.

It’s important to be aware of two characteristics of carbonized wood. First, the heat treatment makes the wood a bit more brittle, which is why you generally only see engineered wood flooring products that are carbonized. In a solid carbonized wood floor, the tongues would break off too easily when nailed.  Second, carbonized wood tends to fade more under UV exposure than the same wood that has not been carbonized. While natural (non-carbonized) Oak changes relatively little when exposed to sunlight, carbonized Oak can fade as much as Walnut, a species known for its photosensitivity. Customers who have intense light conditions in their homes (such as floor-to-ceiling, south-facing windows) should be advised of this before finalizing the selection of a carbonized Oak floor, just as they should for Walnut, Brazilian Cherry, and other species that tend to fade when exposed to too much direct light.


Like fuming/smoking and carbonization, reactive stains (sometimes called ‘active stains’) take advantage of the naturally occurring compounds in the wood to create new colors. Rather than relying on pigments like traditional stains, reactive stains employ carefully selected chemicals that interact with the tannins, extractives and sugars in the wood to change the color from within. Reactive stains are an excellent way of creating an aged look in new wood, as they can replicate the oxidative processes that occur in wood when it is exposed to the elements.

Tannin and sugar differences between boards result in color differences with all of these reactive processes, but with reactive stains, the grain direction also matters. The degree of reaction depends in large part on how much reactive stain is applied and absorbed into the wood. Depending on the grain structure, some areas absorb more than others.  As a result, reactive stains can create significant variation even within the same plank. Rather than being a problem, this phenomenon actually serves to enhance the perception that the wood was colored by nature. The color follows the grain, and the variation within individual boards helps blend all of the boards together.


Due to the enhanced variation created by these reactive color processes, it is impossible to represent these beautiful floors adequately in a sample panel. When all we can see are three small pieces, and each is a different color, it can be shocking. A small panel that shows the extremes only has room for the extremes, and the overall look of the installed floor is lost. For some consumers, it’s hard to imagine how attractive those colors will be when they are sprinkled together in a larger area.

So that customers can fully appreciate these natural color processes, we encourage them to view as much material as possible to help visualize what the floor will look like when it’s fully installed. Photographs are helpful, but an even better way is to get a few cartons of the flooring and lay them out in the space. We want our customers to experience this beauty before they make their decision, and are willing to take returns if they are not happy with what they see. It rarely happens. When the cartons arrive, be sure to lay out all of the material, spreading the color variation around so it can be viewed as a whole. Pulling just a handful of planks out and making a decision too quickly is a mistake. Almost always, the color variation grows on people, and the more area they see, the more they like how natural the floor looks. Rather than being a defect, the variation is truly these products’ greatest asset. Traditional stained floors simply can’t compare to the natural feeling and enduring visual interest created by these special coloring techniques.




The majority of Monarch Plank’s products (and 100% of our Oak products) are made with European Oak. Some people refer to European Oak as ‘White Oak,’ but the truth is that European Oak is quite different from the wood that we call ‘White Oak’ here in North America. Botanically, European Oak and White Oak both belong to the genus Quercus, which contains over 300 species, but they are composed of completely different groupings of species within that genus. Differences between European Oak and White Oak include:

  • - European Oak is more uniform gray in color, whereas White Oak tends to have more yellow and pink undertones
  • - European Oak tends to have tighter grain than White Oak
  • - European Oak tends to be more knotty than White Oak
  • - European Oak has higher tannin content than White Oak, making it more rot-resistant and more suitable for fuming/smoking and other natural color processes

Both European Oak and White Oak feature significant variations in color and grain caused by a variety of factors. These include: differences within a tree, age of the tree, rate of growth, soil and climate of the region, and most importantly, the genetic differences between the various species within each group.


The predominant species of European Oak are Q. robur and Q. sessilis. Other European Oak species of lesser significance include: Q. afares, Q. macranthera, Q. longipes, Q. imeretina, Q. iberica, Q. pedunculiflora, Q. lamugnosa, Q. farnetto, and Q. mirbeckii. In many areas these species grow side-by-side and easily hybridize.

In Q. robur, the branching of the trunk occurs at a lower level, making the wood more knotty. Q. sessilis is tall and slender, with fewer low branches and consequently fewer knots. The wood in Q. robur is generally more dense than in Q. sessilis, and usually produces a wider-grained wood. The fact that Q. robur is wider-grained but also more dense seems to be a contradiction - see below under ‘TIGHTNESS OF GRAIN & DENSITY’ for an explanation of why this is the case.

Some of the Oak that is sold as 'European Oak' is actually from the Russian Far East and consists mainly of Q. mongolica, a species that doesn't grow in Europe at all and has very different characteristics from true European Oak. Due to its proximity to China, a major wood flooring manufacturing center, this Q. mongolica is actually what's being used in many of the products now being sold mistakenly as 'European Oak.'


The main species of White Oak in North America is Q. alba, which constitutes about 45% of the standing White Oak timber. Other species that may be sold as ‘White Oak’ include Q. prinus, Q. bicolor, Q. mueh. lenbergi, Q. stellata, Q. macrocarpa, Q. Iyrata, and Q. durandii. Most White Oak lumber sold in North America contains some percentage of Q. alba, and that percentage can be close to 100% in some forests in the Great Lakes region. In Northern Appalachia and the forests of Missouri and Kentucky, White Oak tends to contain a higher percentage of Q. bicolor and Q. macrocarpa. Wood from Arkansas and the South is likely to contain a higher percentage of Q. prinus and Q. Iyrata.


Across all species, the tightness of the grain is determined by the growing conditions of the tree. A slower growth rate will result in tighter grain.

People generally assume that tighter grained wood is more dense. In most species groups, that is true, but not in Oaks. In Oaks, the spring growth consists of large open vessels, whereas in summer growth, the pores are relatively small. A slower rate of growth (tighter grain) is characterized by a greater proportion of spring wood and a smaller proportion of summer wood. So, in a slow growing Oak tree, due to the higher proportion of large, open, hollow vessels, the wood is less dense. Wood from a fast-growing Oak tree (wider grain) will be more dense. Some companies market their Russian Oak as being more dense than Western European Oak because the cold Northern climate makes for slow growth and tighter grain, but in fact it’s the reverse – the Russian Oak is less dense.


In addition to the fact that true European Oak (from Western Europe) is more dense than Russian Oak, we also find that it has a more beautiful grain structure. Oak from Russia, especially the Far East, usually features black veining running parallel to the grain, a characteristic of American White Oak whose absence in true European Oak is one of the things that makes it so attractive. But those aren’t the only reasons we avoid Russian Oak.

Monarch Plank takes great care to source its wood with the utmost environmental responsibly. All of our raw material comes from verified legal, selectively harvested forestry operations. We source wood only from U.S. and European forests, where forestry laws are strict and well enforced, and from rubber plantations, where the wood is salvaged after the trees no longer produce latex. (Rubberwood, aka Hevea, is dense and extremely stable, providing an excellent substrate for some of our engineered floors.)

Unfortunately, illegal and otherwise irresponsible harvesting is currently commonplace in Russia. Illegal logging is a problem throughout Russia, but particularly in the Russian Far East, where harvesting of Oak and other species on a massive scale is reducing the last remaining habitat of the endangered Siberian Tiger. Due to the slow growth rates in these cold northern forests, it will take a long time for the ecosystem to recover. Most of the Oak being harvested in the Russian Far East is processed in factories in China and sold in the United States, where it is usually labeled as ‘European Oak.’


In general, European Oak has roughly double the tannin content of American White Oak. The higher tannin content makes European Oak more durable (rot-resistant), which is why it was the preferred wood for ship-building throughout European history.  That higher tannin content also allows us to create unique and natural-looking colors via chemical processes that react with the tannins. See ‘CREATING COLOR FROM WITHIN – NATURAL REACTIVE COLOR PROCESSES’ for further details about these coloring techniques.

Within a particular species, localized soil quality and the individual tree’s access to water and sunlight impact the tree’s growth rate, which plays a role in determining tannin content. The large open pores of the spring growth contain more tannin than the smaller pores of summer growth. So, wood from a slow-growing tree with tighter grain (a larger proportion of spring growth) will contain more tannin than a fast-growing tree with wider grain (a larger proportion of summer growth). All other things being equal, trees that grow farther north and therefore more slowly will have higher tannin content than comparable wood from further south.

That being said, in European Oak, genetic differences among species play a much larger role in determining tannin content than does the latitude of the forest or the growth rate of the trees. A different mix of species means that Oak from Western Europe tends to have higher tannin content than Oak from Eastern Europe and the Russian Far East, despite the colder climate. Even within Western Europe, tannin variation in the Oak caused by different species mixtures can be extremely localized. Oak from the Limousin region of France tends to have much higher tannin content than Oak from the nearby Departments of Nievre and Allier, despite the similar climate. This is because the Limousin Oak is mostly composed of Q. robur, whereas the Nievre/Allier Oak is mostly composed of Q. sessilis. In North America, genetics play less of a role in tannin content, as the tannin content among the various species of the White Oak group is similarly low.

The age of the tree when it was cut also impacts tannin content. All other things being equal, older trees have higher tannin content than younger trees.

Even in wood taken from a single log, tannin content will vary significantly from board to board. Tannin is higher near the base of the tree than at the crown, and wood from the outer portion of the tree close to the sapwood is higher in tannin than wood from the center of the log. This means that no matter how carefully lumber is sourced, every batch of Oak will include significant tannin variation