Natural as wood…

Austrian traditions of wood treatment


Created
by Nature
head

Created by Nature

Let’s clarify step by step what is action principle of the natural compounds:

  1.  Penetration into an upper wood layer, its hardening and protection from inside…

Wood consists from cells of various sizes; they are its building bricks. The wooden cells look like long and narrow small tubes built up from cellulose and lignin (natural polymers). Cells diameter makes in average 10-50 µ but can reach 100 µ. Their length varies from fractions of millimeter up to several millimeters or even centimeters.
In wood, also, there are present special larger cells, namely vessels performing the conducting function. Their diameter fluctuates from several micrometers up to 0.5 mm and length from 10 cm up to 3 m.
Look at the photo of a wood under a strong amplification and make your own concept on the extent, to which this porous and peculiar material requires a specific approach to its treatment unlike treatment of non-porous materials.

Wood consists of elongated cells:

Wood cells are hollow; their walls consist of cellulose glued together with the natural adhesive, which is lignin.

Oils and resins in natural compounds consist from small molecules that are hundreds and thousands times less than molecules of synthetic polymers. This is why the natural compounds penetrate easily into the wood cells and cover tightly their walls. The latter does not take place often with polymers (for example with acrylic impregnating compounds) and oligomers (for example, with alkyd impregnating compounds), which lay only onto a surface and are not able to penetrate inside of a cell:

In the course of drying up, oil polymerizes together with a natural resin; and so the cells walls of the wood upper layer are armed with the stable polymer; that is, the wood upper layer is hardened.
Due to the specified reason (see pictures), a synthetic cover is connected with wood weakly, while a natural one is very stable; the latter is practically inseparable from a surface; meanwhile as an additional acquisition, the surface gets wear resistant.
Though, in all fairness, it has to be noted that many aqueous acrylic dispersions (this is a synthetic polymer dispersed in water) and especially dispersions of deep penetration have particles sizes up to 0.1 µ and even up to 0.05 µ (50 nm), which allows them penetrating into a wood cell. But in this case we deal, firstly, with particles of ready polymer featured with low-permeability for water steams; and, secondly, this is just synthetic polymer with its inherent controversial action on human health.

  1.  …and forming of elastic “breathing” protective cover on a surface.

After water getting onto a wooden surface, the following events take place (see picture):

Untreated wood. After coming onto a wood surface, water is taken in quickly into its pores (cells).

As it is seen on the picture, the untreated wood soaks in the moisture as a sponge as the cells walls are wetted with water very well.
A wood treated with a natural compound, does not draw water in as its cells walls are absolutely not wetted with water. In this case in order that water would be able to penetrate into the treated wood pores, one would need applying a strong pressure to water.

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Water drops on a wooden surface treated with a natural compound. Liquid water is not able to penetrate into depths of wood, so it lays on the cells surfaces due to the fact that the cells walls, on which the compound was applied, got water-repellent properties.

So this way, a phenomenon is reached similar to the “lotus effect”: water does not wet lotus leaves because of tiny villi, on apexes of which it flows down from a leaf:

Lotus leaf structure. A water drop is not able to wet the water-repellent micro-crystals of the wax covering micro-cells apexes

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Lotus leaf photo. Water is present on the surface in a form of mobile balls.

As it is seen from the pictures, the micro-structure of the wood treated with the natural compound gets practically identical to micro-structure of the lotus leaf.

 

A wood treated with a common synthetic polymer compound is not wetted, too, as on its surface, a film forms shutting wood cells.

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Water drops on a wooden surface treated with a synthetic compound. The water can not penetrate through the cover film.

A film of a synthetic compound consists mainly of long polymer molecules, size of which is usually much more big than the same of wood cells; on entry into them, such compound forms a solid tight film impermeable for air and water steams. That is why neither air not water steam are not able to penetrate into wood cells – So the wood loses its ability of “breathing” (see picture).

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Water steams (blue arrows) penetrate freely through a wood surface treated with a natural compound.

A film of a synthetic compound consists mainly of long polymer molecules, size of which is usually much more big than the same of wood cells; on entry into them, such compound forms a solid tight film impermeable for air and water steams. That is why neither air not water steam are not able to penetrate into wood cells – So the wood loses its ability of “breathing” (see picture).

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The water steams (blue arrows) are not able to penetrate into the wood treated with the synthetic compound – So the wood loses its ability to “breath”.

Why is it important that a treated wood would be able soaking in water steams as effectively as untreated wood does? Because in this case, one of the main wood benefits conserves, namely its ability to maintain a normal humidity level in a room, as it serves a kind of moisture accumulator, gratifying to which in the room it is always comfortable, without an increased humidity or dryness. The wood treated with synthetic film-forming compounds loses this most important feature.

Wood cells are hollow and filled up with air containing water steams. In a case of natural wood sizes decrease under frost action as well as under air humidity fall, the water steams containing inside of wood are tended to leave the wood. Besides, during operation, any wood, even one treated with film-forming synthetic compounds, is able to absorb moisture step by step, if the wood is not treated hermetically from all sides or there is a cover damage. In case of a considerable changing environment conditions, the moisture release process takes place rapidly and unavoidably. That is how is happens at wood with different treatment:

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Through the wooden surface treated with a natural compound, the water steams can be freely released outside, as the wood pores (cells) stay open and the natural cover on their walls is also permeable for the water steams because of an absence of long polymeric molecules in them.

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As for the water steams being released through the wooden surface treated with a synthetic compound, in course of time, they cause cover swelling (bubbles forming) and cracking of the cover. Among reasons for this phenomenon, there are inpermeability of a synthetic polymeric film for water steams & air and a weak connection with the surface as the polymeric film does not penetrate into the wood near-surface layer.

As a result, a wood with natural treatment behaves as untreated one and releases steams freely, while a wood treated with a synthetic film-forming compound would be subjected to a progressive destruction because of film integrity violations (see pictures).

Of course, it is probable that an occurring-once process can not to destroy a film cover but if this happens on a regular basis during 2 or 3 years and especially outdoor, the cracking and exfoliation process gets visible with the naked eye.

The reason of such compounds behavior (natural and synthetic ones) is a great difference of their molecules size and viscosity. At the natural compounds, the molecules are small and the viscosity is low, so their molecules (those of oils, resins and waxes) penetrate easily into wood cells. As for the synthetic polymeric compounds, their molecular chains are too long and viscosity is high enough; and that is why they do not penetrate into wood cells but instead clog them badly, even in a case that they are applied in a much diluted form.

 

  1. Natural compounds can form a film on a surface either.

Also natural compounds as well as synthetic ones can form a film on a surface shutting wood pores. But here there is some important peculiarity:

I) Presence or absence of a film depends on a compound composition, applied amount and a technique of application. As for compounds with an increased viscosity applied in several layers, as a rule except of penetration into wood cells, they form a film on the surface shutting the cells.

II) Unlike the synthetic polymers, a film formed by the natural oils and resins distinguish with a porousness and is permeable for water steams because of an absence of long polymeric molecules in the cover; this reason is exactly gratifying to what for film-forming natural compounds, the steam-permeability changes insignificantly. Certainly, the thicker the film is, the less it is permeable. So at the glazing lacquer, the steam and air permeability is several times lower than the same of a cover formed with a glazing compound, oil or a wax.

III) A natural film is very elastic and is not destroyed when natural wood sizes change. A synthetic film is much less elastic and due to this reason it cracks easily, aside from its destruction under action of water steams described in the previous point.

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The natural compound is applied with an excess and forms a film on the wooden surface. The film formed of natural oils and resins does not contain too long polymeric molecules even after complete drying up (the polymeric connections are shown with the lines). This is why it remains permeable for the water steams that are free to penetrate or release from the wood (blue arrows). Liquid water is not able to penetrate into the wood through the cover film.

The small thickness of the film and the small size of the natural compound molecules allow conserving cover permeability for air and steams even after drying up and polymerization.

So natural compounds completely conserve wood ability to water-exchange; and besides, the covers do not crack protecting the wood during many years of operation. In this their global advantage over film-forming synthetic compounds consists.

 

  1. Natural wax strengthens water-repellent and mudguard properties of natural compounds increasing their air and steam permeability.

Special protective properties in combination with high water-repellent and mudguard abilites are added to the natural compounds by the natural waxes.

Let’s consider waxes action in more detail. The wood itself uses wax-like substances for their cells protection against water penetration and depredators: those substances are cutin and suberin. Their forming process takes place on a stage of wood young cells lignification. The cutin or suberin is accumulated in wood cells walls and performs the protective function conserving them. In the course of the wood treatment, cells membranes on the surface are destroyed, which lowers their protectiveness drastically.

Carnauba wax is obtained from leaves of carnauba palm; being situated on the leaves surface, this wax protects the leaves from tropical rainfalls & tropic sun ultraviolet and does not prevent their breathing. Without the wax, which the carnauba palm produces, it will perish.

The natural waxes are used by humans long since; they serve for wood ennobling and protection. Like oils and resins, waxes are not polymers; instead they are substances consisting of very small molecules comparing to polymeric ones. These substances are unique with the feature that on a surface they form a layer, which distinguishes with more powerful water-repellent properties than oils and resins and at the same time it is not a polymeric layer; and the latter means that it lets air and water steams pass especially easily (see pictures below). The wax is not able to be polymerized and that is why its permeability for air and water steams does not change after a cover drying up. Wood “breathes” (its moisture balance changes in a natural way) and at the same time the wood is protected completely against of destructive action of water and contaminants. The wax modifies natural compounds and strengthens their protective properties.

After wood rubbing up by compounds with high content of waxes, on the wooden surface, there forms usually a solid thin wax film, which does not close wood cells. When aqueous dispersions and oil-wax compounds are applied scarcely, as a rule, wood cells are not clogged but instead, a wax cover forming takes place inside of the cells, namely on their walls. In both cases an extremely high wood resistance to water and contaminants is reached. In the first case, it happens because of a water-repellent film and in the second case due to the fact that water is able neither to wet the wood cells walls covered by wax nor penetrate into them (see picture): this is so called “lotus effect”.

Gratifying to above described structure and permeability, the wax allows wood “breathing”, even in a case that the wax cover closed the wood cells and formed a thin layer on the wooden surface (see picture).

The wax compound penetrates into the wood cells and covers their walls. Also the wax compound can form the film on the wood. The wax does not contain long polymeric molecules and so it is permeable for air and water steams (blue arrows) even in the case of a thin layer forming. Liquid water is not able to penetrate through the treated surface even in a case that on the surface there is no film as the cells walls acquire water-repellent properties (lotus effect).

The wax is fixed on the surface in more stable way, when it is applied in a combination with oils and resins. It increases their air and steam permeability including the case, when the cover is apply above pores and shut them (see picture).

The oils and resins (yellow balls) harden the cover made of wax (orange balls), which adds increased water-repellent properties to them. The wax is not a polymer and that is why being in contact with the dried up (polymerized) oils and resins (the polymer connections are shown as the lines), the wax adds a higher porousness and permeability for air and water steams to them (blue arrows). Just as in the case of pure waxes and oils, the liquid water can not penetrate into the wood through the cover film; the impermeability is forms also gratifying to water-repellent properties of the wood cells walls after treatment (lotus effect).

So wax ensures the excellent water & mud protection (see picture earlier); besides, wood is able to absorb only water steams but not liquid water (see picture earlier) and as a result, inside of the wood, a humidity level favorable for fungi growth is not reached.

Besides, beeswax contains bio-active substances, in particular remains of propolis, gratifying to which it exerts a natural protective influence upon the wood against fungi and insects. The beeswax is a natural antiseptic. Besides, it is absolutely not subjected to atmospheric factors action, such as sunlight or ultraviolet.

 

  1. Remark on taking care of treated surface.

As some natural compounds can leave wood cells open, in a case of a frequent contact with a cover, contaminants can get into them and stay inside, which can be easily removed with water & soap or with a non-abrasive neutral detergent. The natural compounds forming a film on a cover do not need such taking care as a rule; it is enough to wipe them with a wet tissue or wash with water just like common non-porous synthetic covers.