Bog oak is one of the most valuable types of wood. It is used for making artistic and decorative items. But the extraction and processing of bog oak is a long and expensive process. Therefore, the price of the material is high. Drying stained wood using traditional methods is problematic due to the nature of its structure. How to dry bog oak In compliance with all technologies, we will tell you in more detail.
Bog oak is mined on the banks of rivers. Wood can lie in water for more than a hundred years, and then it is taken out and processed. Products made from stained material have a pleasant dark color and are durable. In terms of density, moraine material is compared to iron, so even sawing it is difficult. The humidity of the freshly mined product can reach 117%. Compared to natural humidity of 50–65%, this figure is impressive.
The material is extracted in three ways:
- For bottom-depth work, it is the most costly and painstaking.
- When developing peatlands, it is less labor-intensive.
- Manufacturing in specialized workshops is the simplest, but multi-stage method.
The weight of wet oak wood is 1500 kg/1 cubic meter. Therefore, immediately after extraction from the water, the material is cleared of silt and sand and cut into small pieces. Otherwise, transportation becomes more difficult.
The tree is afraid of sharp contacts with hot air and direct sun rays, therefore drying is carried out in a gentle mode. A proven old-fashioned way of drying bog oak is to place small blocks of wood in the grain in the fall and leave until spring. Natural drying is also allowed, but it must be carried out in a room with good ventilation and constant humidity and temperature. It became possible to dry the material in a short time only in the last 10 years, with the advent of new technical means.
The following methods are used to dry bog oak in a short time:
- Vacuum chamber.
- Pulse.
- Adsorption.
- Infrared.
But when dried in chambers, moraine material discolors and becomes less dark. Therefore, many criticize unnatural drying methods. But as it dries naturally, the areas exposed to the sun also become lighter. Chamber drying of bog oak saves time, and if it is carried out in compliance with the technology, then cracks will not appear and the product will not be subject to internal stress.
When chamber drying to different humidity levels, minor changes are allowed geometric shapes. But if you pre-treat the product chemical composition, then the changes decrease. Details are shown in the table below:
| Humidity indicator | Changes in geometric shapes, % | |
|---|---|---|
| Chemically treated wood | Unprocessed | |
| 50% | 3,5 | 7,2 |
| 25% | 4,8 | 10,7 |
| 15% | 6,3 | 12,6 |
As chemical treatment a penetrating antiseptic solution is used. The product is soaked in it for 2–3 hours. Drying is also affected by the temperature in the chamber and air humidity. The maximum permissible temperature is 50 degrees - maximum shrinkage. Smaller changes are acceptable when temperature conditions 25 degrees.
Main processing steps
How to dry oak in various ways Let's tell you in more detail. The technology is followed step by step and skipping one of the stages is unacceptable. Otherwise, the wood will crack and become brittle.
Vacuum effect
Vacuum drying oak is carried out in special chambers, where under the influence of low atmospheric pressure pulled from wood excess moisture. It takes place in several stages:
- Bog oak is soaked in an antiseptic solution for 2–3 hours. Sanezh will do.
- The product is placed in a drying chamber, where it is kept at a temperature of 25 degrees and a humidity of 50% for 5 to 10 days. Temperature and humidity must be constant.
- The oak is placed in a sealed chamber, where, under the influence of a vacuum, it is treated a second time with an antiseptic solution.
- Dries at a temperature of 35 degrees and humidity not higher than 25% for 10 days.
The method has advantages:
- Oak wood dries to a predetermined temperature.
- Only 2-7% color change.
- Fully ready within 4-5 weeks.
Of the minuses stand out high costs on energy and process complexity. If you do not monitor humidity or temperature, the wood will crack and become unusable.
Pulse method
The pulse method of drying bog oak is rarely used in Russia due to high costs. But it is considered effective and the material dries evenly.
Performed in the following steps:
- Conductors are connected to the wooden blank on both sides.
- The second ends of the conductors are connected to a special electrical appliance that will supply current.
- Under the influence of electrical impulses, the workpiece gradually dries to the required humidity.
If you have the skills and knowledge, then you can assemble such a device with your own hands and use it for work.
Adsorption method
The adsorption method resembles the old one and is available to everyone at home. To dry, a small piece of oak is placed in a material that absorbs moisture as much as possible. Craftsmen use special mineral granules. But newsprint will do.
Drying is performed in the following steps:
- Small pieces are soaked in a container with an antiseptic solution for 3–4 hours. But you should not use solutions with bleaching effects, otherwise the black color of the valuable breed will disappear.
- The workpiece is wrapped in several layers of paper and placed in a well-ventilated and dry place.
- Every day the product is unrolled and folded into new sheets of newspaper.
Drying is carried out for 1–2 months. The wood will not crack and will retain its noble shade.
Infrared plates
Infrared light heats the wood evenly and drys it gently. The workpiece does not heat up and no internal deformation is observed. The method is available in enterprises and at home. It is enough to purchase several infrared heating elements and place them on a frame made of timber or metal.
Drying is carried out in the following stages:
- The workpiece is soaked in an antiseptic solution for 3–4 hours.
- Place on a flat surface under infrared heaters.
- Once an hour, the workpieces should be turned over so that the heat is distributed evenly.
Humidity is checked using a manual moisture meter. When the product dries, it is allowed to rest for 3–4 days in a dark and cool place with a humidity of 15–25%. Then use it for its intended purpose.
The advantages of drying under infrared plates include:
- The wood does not deform or crack.
- Does not lose its black color.
- Drying occurs evenly over the entire depth and length.
- Electricity costs are minimal.
The method has no disadvantages, but due to its novelty it is little trusted. The video below details one of the available ways drying hardwoods:
How to properly dry bog oak is the secret of woodcarving masters. It was passed from father to son and carefully preserved. But with the advent of new technologies, it is not difficult to dry stained wood at home. The main thing is to follow technology and adhere to our instructions.
Bog oak is one of the most precious species and a valuable resource, which is widely used for the manufacture of decorative and artistic products. It has excellent aesthetic characteristics, increased hardness, but also high cost due to the complexity of the drying process. Due to the high density of the structure, it is quite problematic to obtain high-quality stained wood during natural drying. But modern technologies made it possible to dry wood taking into account all the characteristics of the material in a short period of time and with a minimum percentage of defects.
Features of bog oak processing
Extraction and processing of bog oak is non-standard process which is very different from harvesting spruce, pine or other conventional wood. Blank of this material can be carried out in natural conditions during peat extraction or deep work in river beds. In the first case, wood is extracted during the development of a peat bog. In the second case, oak deposits are determined by careful exploration of river channels, and extraction is scheduled only during the lowest water level in the river.
In addition to natural methods, to obtain bog oak they use a simple but multi-stage technology for harvesting material in special workshops.
As a result of a long stay under water, oak acquires a noble dark color and density comparable to iron. Only carbide tools are suitable for cutting it. Moreover, the drier the material, the harder it becomes.
Due to the high natural humidity of wet oak, reaching 117%, its weight is 1500 kg per 1 cubic meter. This makes it difficult to transport, so the wood is cut almost immediately after it is taken out of the water, and only then is it sent for drying. Bog wood is difficult to withstand exposure to large flows of hot air and direct sunlight, and when dried naturally it requires a stable temperature, good ventilation and a huge amount of time. But modern technologies have made it possible to dry the material efficiently and in the shortest possible time, using the following methods:
- pulse;
- vacuum (chamber);
- infrared;
- adsorption.
Some argue that unnatural drying leads to lightening of the material, but when drying under natural conditions this is also possible. At the same time, unlike the last option, chamber technology saves time, increases productivity, and reduces the likelihood of cracks. To reduce possible deformation of the wood, before drying it is recommended to first place it in a chemical solution penetrating action. But even with such preparation, it is necessary to accurately monitor permissible temperature, which can vary from 25 to 50°C.
Main processing steps
To minimize the overall percentage of defects, each bog oak drying technology requires compliance with a certain stage. Failure to follow the step-by-step procedure will lead to internal stress in the material, which will make it brittle and provoke the formation of cracks.
Pulse technology
The pulse technique involves exposing lumber to electric current. This technology is considered the most effective, as it guarantees uniform drying of stained wood without deformation. But it has one significant drawback - high costs when procuring large volumes of material. Pulse drying includes two main stages:
- Connecting two or more conductors from the end sides of each workpiece.
- Connecting the free ends of the conductors to a device that supplies current in a pulsed mode. Under its influence, the wood gradually dries and is brought to the required moisture level.
While this method is not suitable for large-scale preparations of bog oak, it is quite acceptable for drying single specimens. Moreover, a device of this type can be assembled independently, having special knowledge or having certain skills in installing electrical equipment.
Drying in a vacuum chamber
For this type of drying, chambers are used where moisture is removed from the wood due to low atmospheric pressure. The entire process should take place in the following order:
- The lumber is kept in an antiseptic solution with a penetrating effect for at least 2 hours.
- The prepared oak is placed in a drying chamber at a constant humidity of 50% and a temperature of 25°C, depending on the thickness of the blanks, for 5–10 days.
- After this period, the wood is moved to a completely sealed compartment for re-treatment with an antiseptic and drying at a humidity of up to 25% and a temperature of no more than 25% for 10 days.
Thus, the wood dries to the required moisture content in just a month with a color change of 2 to 7%. The disadvantages of vacuum technology include the complexity of this process and high energy costs.
Infrared drying
Drying using infrared rays is considered one of the most gentle. It allows you to dry lumber evenly without heating or deforming it. Due to the availability of equipment and low energy consumption, this method It is successfully used both in large enterprises and at home. To do this, you only need to purchase a few infrared heaters, which are then placed on a pre-mounted metal or wooden frame. After erection of the structure, drying is carried out in several stages:
- The oak is soaked in a solution with an antiseptic for at least 3 hours.
- It is then placed on flat surface, so that the heat from infrared heaters is distributed between the workpieces.
- To obtain uniform drying, the lumber is turned over once an hour. The workpiece dries with equal humidity throughout its entire depth and length.
During the drying period, humidity is determined manually using a moisture meter. Once the desired humidity is achieved, the wood is allowed to rest for about 4 days, placing it in a cool room with a humidity of up to 25%.
Adsorption method
The adsorption method is one of the most ancient technologies. Its main advantage is the availability of use at home. To dry by adsorption, oak wood is placed in a material that absorbs moisture well. Regular newsprint can be used as such material, but most often special granules with a mineral composition are used. Drying using adsorbents is carried out in several steps:
- Pre-soak the lumber in an antiseptic solution for 3 or 4 hours. For this procedure, only antiseptics that have no whitening effect are suitable. Otherwise, the oak will lose its dark, valuable color.
- Extracting the rock from the solution and drying it with paper.
- The wood is then placed in dry room with good ventilation and wrapped in 3-4 layers of paper.
In order to ensure high quality drying, the bog oak is unrolled every day and covered with new sheets of paper. Drying by adsorption method takes from 1 to 2 months. During this time, the tree reaches the required indicators of importance, completely retains its shade and does not crack.
Let's summarize
Proper drying of bog oak requires not only knowledge of all the features of this material, but also precise adherence to technology. Only in this case, industrial and home production wood will be successful, maintaining productivity at the highest level.
Aralova O.V.(VGLTA, Voronezh, Russian Federation)
Shrinkage of a wood fumed oak’s values that was subjected to preliminary thermochemical processing and raw are investigated. Conformities to the lawof influence to processing modes on shrinkage size are established.
Bog oak wood has a very beautiful appearance, and for this reason it is a valuable decorative material. Highly artistic products and crafts are made from this material. Recently, there has been an increase in demand for bog oak wood.
The high price of this material is due to the complexity of its extraction, storage and processing. Perhaps the greatest problems in wood processing technology are associated with the drying process. Traditional methods do not provide high-quality drying of bog oak wood.
For a number of years, research has been carried out at the Department of Wood Science of the Voronezh State Forestry Academy to develop a technology for drying bog oak wood. The developed technology of chamber drying with preliminary thermochemical treatment ensures high-quality drying of bog oak wood. Wood dried in this way is characterized by high dimensional stability.
However, in the process of preliminary thermochemical treatment, thin layer hygroscopic solution, which affects the hygroscopic properties of wood.
One of the main physical properties of wood that affects the size of products and depends on the amount of moisture absorbed by the wood is shrinkage. The purpose of this work was to study the amount of shrinkage of wood treated with this method.
Experimental studies were carried out on bog oak wood taken from the river. Voronezh.
Wood selection was carried out in accordance with GOST 16483.21−72. Blanks with a cross-section of 20x20 mm were cut from round timber of bog oak wood for subsequent research.
One part of the samples, measuring 20×20×60 mm along the fibers, was subjected to preliminary thermochemical treatment in a hygroscopic solution for 3 hours. Then all processed workpieces were sawn into samples measuring 20x20x30 mm, the latter along the grain. The second part of the blanks, unprocessed, was sawn into samples of the same size and used for control. Then the samples were placed in desiccators, at the bottom of which sulfuric acid of a given concentration was poured to maintain a given relative humidity.
Desiccators with acid solution and samples above it were placed in drying cabinet, in which a constant temperature of 50 °C, 80 °C and 20 °C was maintained. The relative air humidity in the desiccators was maintained at 52-54%.
The results of experiments to determine shrinkage are presented in Fig. 1 and 2.
Figure 1 - Dependence of shrinkage of thermochemically treated bog oak wood in the tangential direction on humidity, at different temperatures drying
Figure 2 - Dependence of shrinkage of untreated stained oak wood in the tangential direction on humidity, at different drying temperatures
Analysis of the results shows that Drying of thermochemically treated wood is significantly less compared to untreated wood. The greatest reduction in shrinkage is observed when drying at a temperature of about 50 °C. In this case, the shrinkage value for the treated wood was 3.5% and 7.2 % – for unprocessed. At a drying temperature of 80 °C, the shrinkage was 6,1%, and with atmospheric drying in room conditions(20 °C) the shrinkage amount was 7,1 %.
For untreated wood, shrinkage at temperatures of 20 °C and 80 °C was respectively8% and 8.5 %. The least shrinkage of stained oak wood, and therefore its greater dimensional stability, was observed when dried at a temperature of 50 °C, for both treated and untreated wood.
An analysis of the nature of shrinkage of stained oak wood at temperatures of – 20 °C, 50 °C and 80 °C and a relative air humidity of 52-54% showed that the amount of shrinkage of stained oak wood is the same as that of natural oak. Minimal shrinkage of bog oak wood is observed when drying at a temperature of 50 °C and a relative air humidity of 52-54%. Maximum - when drying under natural conditions (temperature 20 ° C and 80 ° C, and relative air humidity 52-54%. Maximum drying under natural conditions is explained by the absence of internal stresses restraining drying. When high temperature and a relative air humidity of 52.5%, the increase in shrinkage is presumably explained by the appearance of collapse, as in natural oak wood, due to the destruction of some anatomical elements.
Thus, as a result of the experimental studies, it was established that in order to reduce the amount of shrinkage and increase the dimensional stability of products made from it, it is advisable to subject bog oak wood to preliminary thermochemical treatment and drying to the required final humidity in chambers at a temperature of about 50 ° C. The layer formed on the surface (about 0.5 mm) from the hygroscopic solution is easily removed by subsequent mechanical treatment.
Literature
1. Kuryanova, T.K., Platonov, A.D., Petrovsky, V.S. Drying of hardwood with preliminary thermochemical treatment [Text] / T.K. Kuryanova, A.D. Platonov, V.S. Petrovsky //Forest Journal. – 2004. - No. 4. – P.58–63.
Oak is a very popular material that is widely used:
- Construction.
- Finishing work.
- Making furniture.
- Making art objects and souvenirs.
Naturally, not only freshly felled and sawn wood is used, but processed and high-quality dried material. This is a prerequisite to avoid future cracking, changing the shape and size of the product. Oak, which is used in construction or furniture making, must have certain physical and mechanical properties.
Therefore, when the sawing is completed, the question arises: “ How to dry oak correctly" We will answer this in this article.
Features of oak wood: what should happen as a result of drying
Oak lumber is quite capricious; it is difficult to dry naturally. It is not enough to simply leave the stack under a canopy or in the open sun so that through certain time get the required result.
Before how to dry oak boards, you need to understand the features of the material:
- Oak wood is susceptible to drying. This means that when the moisture level drops below a critical level, internal and external cracks can form.
- The most difficult thing to dry is freshly sawn oak, whose humidity exceeds 25%.
- Temperatures above 55 degrees are not allowed initial stages drying. This leads to the collapse of wood capillaries, that is, to the appearance of multiple internal cracks.
- It is not recommended to send freshly sawn material with a humidity above 40% for drying.
- Proper drying of oak requires maintaining a certain level of temperature and humidity.
Features of drying oak wood are such that to obtain quality material without defects with a certain percentage of humidity, it is necessary to draw up a preliminary plan for this procedure and use special means.
There are several tasks for drying oak:
- Shrinkage with prevention of changes in linear dimensions. Here the humidity is reduced to 30%.
- Drying to transport humidity of 20-22%.
- Full volume drying for immediate use. The humidity level should be 6-12%.
Methods of drying oak: chamber and chamberless methods
From all of the above, it is obvious that obtaining wood from freshly felled oak that meets all the necessary parameters is a labor-intensive and time-consuming process.
There are many ways to reduce the moisture content of boards, logs and beams, but they can all be divided into two large categories:
- Tubeless (atmospheric) drying.
- Chamber drying.
Atmospheric drying is ideally the most affordable and in a natural way reducing humidity levels. The technique has been used in sawmills and wood processing industries for centuries. It is believed that naturally dried wood is of the highest quality and can be used for decades without changing its original qualities. But there is one way significant drawback- time extension.
Because modern life very dynamic, buyers are interested in purchasing material as quickly as possible. Logging enterprises, in turn, prefer to sell wood in as soon as possible. Therefore, in XIX-XX centuries Many techniques have been invented using electrical energy. Chamber drying is carried out in convective chambers; condensation and vacuum drying are also used. 
All work is carried out in industrial conditions, as a rule, are divided into the following stages:
- Warm up
- Direct drying.
- Cooling, obtaining a given humidity threshold.
Chamber drying is similar to multiply accelerated atmospheric drying; the desired result is achieved many times faster. But the disadvantage is the high cost of the procedure. It is necessary to use expensive equipment; most often this is only possible in industrial conditions.
Fortunately, not so long ago infrared dryers appeared, which make it possible to reduce the time required for atmospheric drying and obtain the desired result in a time comparable to chamber processing. At the same time, all Features of drying oak wood, the material does not experience aggressive influences that destroy the structure. At the end of the process, the humidity reaches the required level.
Infrared drying of oak: advantages of the modern method
Proper drying of oak has now become possible even at home. Infrared dryers manufactured under the FlexiHIT brand have a cassette form factor, are easily located inside stacks, and can also be used for drying small pieces of material. IN in this case The volume of wood does not matter, it is enough to use required quantity dryers and position them correctly. The result is achieved in 3-7 days.
The properties of infrared-dried oak correspond to the properties of wood dried by the atmospheric method:
- The material has a specified moisture content.
- The fibers do not warp, cracks and stressed areas do not form.
- Appearance matches appearance naturally dried oak.
It is noteworthy that anyone can use IR dryers; you do not need to have any special skills to get results. The equipment operates from a regular electrical network and consumes very little. Drying one cubic meter of wood requires no more than 200-400 kW.
To check the humidity, it is enough to use a moisture meter; when the required value is reached, the infrared dryers turn off. The oak can be used for its intended purpose immediately.
Oak wood is quite capricious when dried, so to get the optimal result in the shortest possible time, it is better to prefer tubeless drying in combination with IR dryers.
