Choked wood - why marbled design occurs, pluses and minuses, species, uses

Wood defects, whether they are growth or after felling, do not always make the tree unusable. Sometimes the defect is so spectacular that the wood in question is sought after and appreciated by craftsmen and wood enthusiasts. This is the case with choked wood (shovelling woodwhich fascinates with its marble-like pattern. The transformation, which takes place naturally under the action of micro-organisms and fungi, brings to life spectacular patterns and shades, offering a particular artistic and aesthetic dimension. The wood affected is predominantly deciduous wood, especially that showing false heartwood - beech, hornbeam, hornbeam, pine. Read on about the formation process of suffocated wood, its pluses and minuses, as well as its possible uses in various projects. Thanks to Daniel Szekely (Apprentice Dani) for his support in documenting the topic.

Suffocation - a phenomenon that colors the wood but alters some of its mechanical properties

Defects that change the color of wood are known as abnormal coloring and alterations. CAbnormal colorations are characterized by a change in the colour of the wood from the normal colour of the species, without noticeable changes in mechanical strength. They occur as a result of attack by micro-organisms, bacteria, fungi or other stress factors and may be zonal or throughout the wood. Such abnormal discolorations are cornflower woodi, false heartwood, lunula.

Changes are caused by xylophagous fungi, i.e. fungi that feed on wood components (cellulose, hemicellulose, lignin) and lead to changes in the color of the wood and important changes in its properties. The best-known alterations are smothering, also known as scorch, and rot.

Suffocation (upheaval) is a coloured wood decay characterized by a change in the colour and consistency of the wood. The process begins with a change in color to a reddish hue which, in cross-section through the log, appears as isolated spots or a single spot spread over the entire surface. This first phase is also called încindere (considered an abnormal coloration because the mechanical properties are not yet affected) and appears especially in species with false heartwood (beech, hornbeam, hornbeam, anise), surrounding the red heart.

In the final stage of bark splitting, whitish patches bordered by black lines appear, giving the wood a marbled appearance and changing its physico-chemical properties. This phenomenon is common in logs that have been felled and left in the forest for a long time under the action of moisture and heat. Natural smothered wood has very low durability and low mechanical strength.

The rot is characterized by significant changes in the colour, structure, chemical composition and physico-mechanical properties of wood. It is caused by the attack of xylophagous fungi, which feed on the main chemical constituents that form the walls of the wood cell. Detailed information on what causes wood decay can be found at here.

The conditions that lead to naturally suffocated wood

Suffocation occurs in the warm season and occurs on felled logs that are not properly stored and treated after felling. The first signs appear on the sides in areas where bark is missing or where the wood has been injured. Spread of the defect occurs mainly longitudinally, but may also occur radially. Fire appears 5-7 days after felling and spreads at 25-40 cm/month. Suffocation occurs at 30-40 days and progresses at 20-30 cm/month.

Natural smothered wood occurs if the necessary conditions are met for xylophage fungi to attack the wood. These are: water, temperature, oxygen and time.

Minimum amount of water in the wood for fungi to grow is 201TPTP3T of the pore volume. This decrease is sufficient for air to enter the wood (oxygen) necessary for their development. If the water content decreases further, the fungi can no longer grow. This is why the logs must be cut and subjected to drying and protective treatments immediately after felling. If this cannot be done, the log must be preserved in such a way that plenty of water remains inside (submerged in water, watered abundantly or with the ends protected to slow down the outflow of water).

Range of temperature in which xylophagous fungi develop is 10-40°C, but between 20 and 32°C their development is very rapid. The fourth important element in the occurrence of smothered wood is time. Too short a time is not enough to get the wood marbled, and too long a time can lead to rot, which makes the wood unusable.

The fungi that first attack wood are those of the Penicillium, Verticillium, etc. groups, i.e. those that feed on the sucrose and albuminoid substances in wood. In the next phase, those which attack the cell wall (Ophiostoma phagi, Hipoxillon Coccineum, etc.) appear, leading to partial rotting of the wood and even to total destruction.

The pluses and minuses of naturally suffocated wood

The aesthetic side is the big plus of this wood defect. The marbled look and the combination of colors give objects made from suffocated wood a special look and charm. It is a wood to the liking of artists, craftsmen who make small decorative objects, those who make different objects combining it with epoxy resin.

The disadvantage is the decrease in physical-mechanical properties. Such wood loses its strength and part of it practically rots. As this is a natural, uncontrolled phenomenon, we cannot know how much it has been affected, which is why it is not recommended for objects requiring strength. It cannot be used in construction and furniture. It also cannot be used outdoors because its durability is very low.

Marbled wood obtained by controlled 'smothering

The pluses and minuses of natural choked wood have led to the emergence of companies producing choked wood. As a highly valued wood from an aesthetic point of view, methods have been sought to control the "colonization" of the wood by fungi in order to make it more resistant. Suffocated wood on the market is produced by world-renowned companiesand their products are highly appreciated by designers, architects and art furniture companies.

Studies on wood-attacking fungi have shown that once certain fungi colonize the wood, they protect their area by drawing demarcation lines to protect themselves from attack by other types of fungi. This is how the marbling pattern appears. The process can only be controlled up to a certain point, but there is no specific pattern that can be replicated. This is why companies that produce this type of wood (solid or veneer) do not work on an industrial scale, but only for the design area.

During the smothering process, different fungi produce pigments that color the wood. The pigments range from delicate shades of white and cream to intense tones of black and brown. The resulting patterns are very diverse, contributing to the unique look of smothered wood.

Different species of wood can be suffocated, but not all react in the same way, as responses to fungal attack can be very different. Some species are more likely to develop interesting patterns and colors, while others may have a more vague response or none at all. For example, beech and maple respond very well, with colors ranging from white to black. Basswood develops subtle and fine patterns, while pine is more subtle, sometimes adding some unusual nuances to the natural look.

Uses of choked wood

The most common natural suffocated wood is that of species with false heartwood - beech, hornbeam, hornbeam. But there is also choked wood from birch, spruce, pine, lime, poplar or willow. Carpenters and craftsmen use this wood to make bowls, choppers, spoons, pens and decorative objects. It is often combined with epoxy resin.

Controlled-suffocation wood can be in solid or veneer form. It is commonly used in sculpture or fine art projects, interior decoration, table tops or unique pieces of furniture. Veneers are used to make guitars or stringed instruments, as controlled choking does not affect the resonance of the wood.

I hope you find the above information useful. As always, additions are welcome. And if you have any questions or queries, please leave them below in the space provided. I will be sure to reply.