Birch wood
| birch | |
|---|---|
 |
|
| Tree species | |
| origin |
Europe, Asia |
| colour |
yellowish white, reddish white to light brownish |
| Material properties | |
| Bulk density mean | 610-650 kg / m 3 |
| Raw density limit values | 460-830 kg / m 3 |
| Axial shrinkage | 0.6% |
| Radial shrinkage | 5.3% |
| Tangential shrinkage | 7.8% |
| Flexural strength | 120 N / mm 2 |
| Compressive strength | 60 N / mm 2 |
| tensile strenght | 137 N / mm 2 |
| Thermal conductivity | 0.142-0.152 W / (m · K) |
| Fuel properties | |
| Calorific value | 4.3 kWh / kg |
As birch wood , the wood two types of birch trees (genus Betula ), of birch ( Betula pendula ) and downy birch ( Betula pubescens ) denotes, as lumber may be used. The shrub birch ( Betula humilis ) and dwarf birch ( Betula nana ), which are also native to Central Europe, are of no importance to the timber industry due to their small size.
Both types of birch have only low demands on the soil quality, the silver birch grows even on the poorest and driest soils, which has earned it the name sand birch. The bog birch also grows on strongly acidic and waterlogged quarry forest soils and bogs. They are medium-sized trees that can reach heights between 20 and 30 meters, with trunk diameters of 50 to 70 centimeters, rarely up to 100 centimeters. It reaches a maximum age of 100 to 120 years, the increase in height ends around 60 years.
In Germany, the birch is of little importance as a timber. In the Scandinavian and Baltic countries and in Russia, however, it plays an important role. Birch is mainly processed as peeled veneer and into plywood panels . Solid wood and sliced veneers are used to make furniture. Birch wood is only used in very small quantities as firewood and is mainly used in house fires .
According to DIN EN 13556, the abbreviation for silver birch and bog birch is "BTXX".
Appearance
Birches are sapwood trees and usually do not develop a color core, while sapwood and heartwood are the same color. The wood is light, yellowish-white, reddish-white to light-brownish in color and has a slightly silky sheen. A yellowish-reddish to brown false core can develop with age. The annual rings are clearly defined by narrow strips of latewood . The wood shows only a few, small to medium-sized, scattered-pored vessels. Characteristic of birch wood is the appearance of reddish brown marrow spots.
The silver birch has two growth characteristics that are considered particularly valuable:
- The flame birch or ice birch shows a flame-like drawing, often described as ice flower-like, which is created by particularly restless grain. The grain of the birch is made up of small bark inclusions that create the flame-like pattern. The flame drawing is genetically determined and can be passed on to new generations through vegetative reproduction and crossing.
- The brown grain formation is caused by bark inclusions that are triggered by a virus infection .
properties
The woods of silver birch and bog birch are very similar. The bog birch has a somewhat finer-grained, heavier and tougher wood. With a density of 650 kg / m 3 and a wood moisture content of 12 to 15%, the birch wood is a medium-weight to heavy wood, but rather soft. It is therefore sometimes counted among the softwoods, such as poplar or linden, but their wood is significantly harder. The wood is tough and elastic and has a medium breaking strength . It is not very weatherproof and not very durable even under water. Birch wood is difficult to split.
Birch wood can be worked well by machine as well as by hand, which is particularly evident when peeling, knifing, profiling, turning and carving . Planed surfaces become smooth, the wood is also easy to bend, but difficult to split. The surfaces can be stained and polished well, the treatment with lacquers is problem-free, only when treating with polyester lacquers there can be delays in drying. Nails and screws hold well, but gluing can cause problems.
use
Birch wood is offered as round wood , sawn wood , as sliced or peeled veneer and as plywood. In Germany, the birch is only of minor importance as a timber compared to other species, but it is of great importance in Russia, the Baltic and Scandinavian countries, in Finland, for example, similar to the beech in Germany. Birch is mainly processed as peeled veneer and into plywood panels, furthermore as solid wood and as sliced veneer for the manufacture of furniture. In addition to plain goods, flamed and grained veneers are particularly popular for home furniture. It is also suitable for imitating more valuable types of wood such as walnut, cherry or mahogany and is also used to manufacture parquet floors .
Birch is often used for turning, sometimes also for wood carving. As a special wood, it is used to make spears and discus discs . In musical instrument making, the hammer handles of pianos are made of birch, but also the backs and sides of inexpensive guitars. Birch wood is used in the copper refinery in the reduction phase. Since it is odorless, food barrels are made from birch wood, for example herring barrels. A high-quality pulp is made from birch and processed into paper, cardboard and man-made fibers.
In the past, birch was used more frequently, for example in wagons , in wagon and vehicle construction. In aircraft construction between the world wars and in glider construction to this day, light but highly stressed aircraft parts were mainly made from waterproof birch plywood. This so-called "aircraft plywood" is available in thicknesses of 0.6-5 mm. In general, the Schleicher Ka 6 (1955–1970) is considered the culmination of wooden aircraft construction .
Skis and sled runners were also made from birch wood. The wooden spools of sewing thread were made almost entirely from birch wood, as birch is the only wood in which a notch cut on the edge of the bobbin to clamp the thread does not crack. Other special uses were the manufacture of wooden nails, tool handles, clothespins, matches and wooden shoes. In the past, “Birkenmaier”, birch beer mugs in which the bark was not peeled off, were popular with fraternity members.
Birch wood is also an excellent firewood and is particularly popular as firewood. With a calorific value of 1900 kWh / rm it has good burning properties. Due to its high density, a storage time of approx. 1.5 years is recommended. Dried birch wood burns relatively quickly with a beautiful bluish flame. Since it burns almost without flying sparks and develops a pleasant fragrance due to its essential oils, it is also very suitable for the open fireplace. The birch bark is also used as a lighter.
proof
literature
- D. Grosser, W. Teetz: Birch . In: Local timber (loose-leaf collection) . No. 18 . Information service wood, wood sales fund - sales promotion fund of the German forest and wood industry, 1998, ISSN 0446-2114 .
- Doris Laudert: The myth of the tree . 7th edition. BLV, Munich 2009, ISBN 978-3-8354-0557-8 , p. 57-63 .
Individual evidence
- ^ Foglia, Sonderegger, Niemz, Bader, Weber: Investigations into the thermal conductivity of novel wood-based materials and material composites. (pdf) In: Research report for the Board of Trustees of the Fund for the Promotion of Forest and Wood Research No. 2004.02. Institute for Building Materials, ETH Zurich, July 2006, p. 4 , accessed on August 15, 2012 .
- ↑ Peter Niemz: Investigations into the thermal conductivity of selected native and foreign wood species . In: Building Physics 29 . tape 29 , no. 4 . Ernst & Sohn Verlag for Architecture and Technical Sciences GmbH & Co.KG, Berlin 2007, p. 311-312 , doi : 10.1002 / bapi.200710040 .
- ↑ Calorific value of wood (part 2). In: Information on alternative energies. Retrieved October 25, 2009 .
- ↑ Laudert: Mythos Baum , p. 59
- ↑ http://www.kaminholz-wissen.de/brennholz-birke.php
