Bending of Wood is a very traditional technique which has key importance in numerous manufacturing industries, especially, in those industries that make wooden furniture, boats, ships, handles, agricultural equipments, and sports goods. Different types of methods are frequently used for making the bent parts of wood. Extensive experience has developed the practical wood bending techniques and the practiced craftsman for applying these wood bending technics.
Mostly, people don’t know about bent wood furniture with chemical or without steam. Today, I will share the information about wood bending techniques with chemical, which are using in contemporary furniture manufacturing industries. These confidential techniques are using in many popular modern furniture companies. Each company has its own confidential techniques for wood bending. They never impart it to anyone. However, I will share a basic idea with you regarding this wood bending technique with the goal that you will be able to research on it as well as would apply in your field of modern furniture manufacturing.
In chemical softening techniques, wood is softened by different kinds of chemical before bending. Ammonia treatment with ammonia gas, ammonia water, and liquid ammonia, alkali treatment, etc are very common examples of chemical softening method in the process of wood bending. Let us discuss the Alkali Softening technique at first.
Process of Alkali softening for Wood Bending
Generally, there are some alkali chemicals named as Natrium Hydroxide, Kalium Hydroxide, etc. used for the process of Alkali softening for plasticize the wood. Normally, a solution form of all these chemicals is used. Thus, a normal pressure and room temperature is enough for the softening process and no special devices, and any heat source is required. Furthermore, just one-time alkali chemicals are applied on the wooden material, at the other while, the material becomes soft provided that the water (dampness) is remained there. However, wait until wood comes to be dry, and add some water for a second time so that the wood became soft again. This chemical softening method also has weakness, which is that the color of wooden material may be changed due to the usage of this chemical. Therefore, majority of timbers change the color of the wood material after softening. The wood material required in this method should have a thickness of 10-20 mm. It implies that chemical softening technique has limited range of use in timber bending.
The wood becomes plastic like ((becomes ductile) after the chemical softening because of the fibre which contracts while in normal condition it is straight. The Wood structure becomes loose in this method, and for that reason, the wooden material bends easily. In addition, the impact of contract/shrink happens just if caustic soda (NaOH) is 6-10% of alkali chemical and caustic potash (KOH) is 10-20% of alkali chemical.
Preparation of Alkali Solution for Chemical Softening
Caustic soda is better to use because it is easy to obtain and very cheap. Firstly, prepare a solution of caustic soda with a concentration of 10-15 %. Now, take 10-15 portion of caustic soda, 85-90 portion of water in weight ratio and the concentration of caustic potash should be about 10-20 %. Lastly, dissolve all the solutions.
Summary for Alkali Chemical Softening Process
- Dip the bent wood strips/wooden material into the solution of alkali chemical for penetrating the chemical.
- .After that, bleach the wood.
- Then, remove it from the chemical solution and dip it into the solution of hydrogen peroxide with the concentration of 3-5% and bleach it again (you may skip it)
- After that, wash this wood with fresh water
- Lastly, start the wood bending until the process of drying.
You can also learn another types of Wood bending techniques: