To enhance its natural durability and to protect it from insects, it is necessary to treat bamboo before use. Below is the natural bamboo treatment process at our factory:
For construction use, mature bamboo between 3–5 years old is selected. It shrinks less when dry and its starch and sugar contents are low so there is less chance of insect infestation. Upon arrival at CLC, the bamboo is separated according to usage.
Different species of bamboo have different uses eg. the smaller bamboo species like ‘pai si suk’ can be stripped for use for weaving mats used as the substructure of our bamboo roofs.
The thicker, more mature bamboo species ‘pai tong’ and ‘pai hok’ are used for structural columns and beams.
Depending on the diameter of the bamboo, different sized drill bits, attached to a long steel rod, are used to drill through the centre of the bamboo culm throughout its whole length.
This is to longitudinally penetrate the bamboo’s nodal diaphragms before the natural preservation treatment.
Here at the bamboo treatment pool, the bamboo soaks in a borax and boric acid solution for 7 days to allow the salts to fully penetrate the inside “meat” of the bamboo.
Bamboo treatment with Borax and Boric Acid
Borax or sodium borate is a soft, colourless, powdery mineral that dissolves easily in water. It is a natural insect repellent and preservative.
After about one week, the bamboo is pulled from the pool and stacked vertically so the preservation solution can drain from the bamboo and be recycled in the pool.
Next, the bamboo poles are left to bask in the sun for 1 week depending on the amount of sunlight here in Chiang Mai. Then we rotate the bamboo poles daily to avoid cracking. The sun bleaches the bamboo to a natural golden yellow colour that is more attractive as bamboo construction material.
As last step of the bamboo treatment, the bamboo poles are left to dry slowly in a cool, dry place until they are used for bamboo construction.