Drying bamboo poles requires more time than wood of similar density. This because bamboo possess hygroscopic materials (compound that easily absorbs moisture) that may contain 50-60% moisture content, depending on the felling season, area of growth and species.
When bamboo dries it contracts and shrinks. This shrinkage starts from the moment the bamboo is cut, and can reduce the diameter of the bamboo poles with 10% to 16%, and its wall thickness with 15% to 17%.
Green bamboo poles should not be used in construction. Since green bamboos are subject to shrinkage, joints and terminals may loosen after just a few weeks. Green bamboo is also more attractive to insects and microorganisms, than dry bamboo.
Important factors when drying bamboo:
Air drying round bamboo takes about 6-12 weeks. Drying time depends on:
* Post-harvesting transpiration is a technique used by peasants or indigenous communities. The procedure takes place on the bamboo plantation, and does not only dry the bamboo stems, it is also a traditional way to preserve bamboo from insect infestation.
The freshly cut bamboo stems are placed on a stone (to avoid soil contact). The stem is placed upright, leaning against another bamboo tree with branches and leaves attached for about 3-4 weeks. This way, bamboo stems lose their humidity progressively true natural ventilation and transpiration true the leaves.
For more information about post-harvesting transpiration see: How to Harvest Bamboo.
* Storing bamboo in water is useful when bamboo needs to maintain its pliability or when it needs to be processed in its "green" condition. Storage in water causes leaching of starch (sugars) and is also used as a traditional bamboo preservation technique.
* Kiln oven drying is at the present level of drying technology not recommended for round bamboos. Even under mild drying conditions, higher temperatures can enhance the incidence of cracking and collapse. Split bamboos, however, can easily be kiln oven dried.