Bendywood® -    The Bending Wood Without Steam


THE HISTORY OF WOOD BENDING

Ancient Egyptians bent wood after heating it by means of steam. The technique of steam bending was continuously developed and reached one of its climaxes before World War I thanks to the Thonet company. With this technique the company produced amongst others the Thonet-chairs, which nowadays are still famous.

The Thonet bending technique involves clamping the steamed piece of wood that is to be bent onto a steel band so that it cannot move in longitudinal direction. Then the wood is bent together with the band. As the piece of wood is clamped, the fibres are not only bent but also compressed and thus a much tighter bending radius can be reached. In addition, after the bending the band can also be used as a mould for drying the bent wood.

Bending by means of steam is a tedious procedure: you need steam machines, bending machines and bending plates and moulds for each piece, in which the bent pieces need to be dried. After the drying the bent blanks are still to be processed and machined.

The Thonet-method demonstrates that compressed wood can be bent much better than wood that is not compressed.

 

"PATENTED PLIABLE WOOD" – HISTORY AND BENDYWOOD®

This wood is the result of a further development of the above-mentioned knowledge.

In 1917 the Imperial Patent Office in Berlin patented the method of making wood flexible in the long term. A quotation out of the original patent document (translation): "Blocks of wood are first steamed and then, when hot and wet, put into the press, where they are surrounded by a thick cover in order to avoid deformation during the pressing procedure. Finally the punches are moved in grain direction. The wood is then dried and after the cooling and drying it does not go back into its former length anymore. As a result of that it remains permanently flexible". Pliable wood, produced by this patented method, is thus called "patented pliable wood".

Already in the twenties the "Gesellschaft für Holzveredelung mbH" (wood refining company) in Essen produced this pliable wood up to a length of 165 cm on self-developed steam and compressing machines. In 1926 another patent regarding this wood compressing method was issued and an industrial production began. The products were sold on the German market: mouldings for furniture and windows, skirtings, frieze edgings, handles, armrests, doorframes and hammer shafts (it is used for hammer shafts as compressed wood does not easily break and also reduces the intensity of the rebound!).

The "patented pliable wood" was already generally known back then: this kind of wood was described in detail in the source of supply listing on page 596 in the type book of aircrafts, for instance, which was published in 1939 by the publishing house Hermann Beyer in Leipzig, as it was also used in the domain of aircraft model making. After World War II the production was continued in Selters/Westerwald and the products were sold not only in Germany but also in every accessible export market at that time (Europe, USA, Far East).

In 1990 the company Candidus Prugger became the successor of the wood refining company in Selters: the production plants and the stocks were brought to Bressanone in Italy and the clients all around the world were further supplied without interruption. In the following years the production process was improved and new products and new markets were developed.

The development of a new compression machine didn't only allow to compress the wood in a continuous way (i.e. uniformly along its entire length), but also to produce lengths up to 220 cm. The steaming and drying procedures were improved and new types of wood like oak, maple, cherry and walnut were added to the product range.

New products, like bending handrails for instance, were created although at first it posed a problem to joint the pliable wood in such a way that the connections were not only accurate but also withstood the pressure during the bending. The problem was solved and now it is possible to produce bending handrails out of pliable wood in standard lengths up to 6,6 m (22') - custom special lengths up to 9 m (30') - and up to a diameter of 65 mm (2-1/2"). The "patented pliable wood" was given the new name "Bendywood®".

 

"PATENTED PLIABLE WOOD" BENDYWOOD® – TODAY

This wood is still produced according to the method patented in 1917: steamed deciduous trees (beech, oak, ash, maple, elm, walnut and cherry) are longitudinally compressed to 80% of their original length. The wood is then dried in this compressed length and can be worked in the traditional way in order to obtain handrails, lippings, wooden profiles for round and oval tabletops, glazing beads, ornamental mouldings and skirtings. These products all have the unique caracteristic that they can be bent in a fully profiled state up to a radius of 1 : 10, i.e. a 20 mm thick moulding, for instance, can be bent up to a radius of 200 mm.

Bendywood® can be stored indefinitely and never loses its flexibility.

So "patented pliable wood" is a raw material that makes it much easier to bend solid hardwood: it is worked like ordinary wood (in order to obtain a bending handrail, for instance) and then it can be bent in dry condition (without using steam) in several directions. It can be used whenever the traditional steam bending method is either not profitable or not possible when dry and fully profiled wood need to be bent.

Since 2003 the pliable wood has been registered worldwide as Bendywood®.