Treatment of Bamboo with Boric acid / Borax

The preservative used is a mixture of boric acid and borax which result in the formation of disodium octaborate, which is easily soluble in water. Boron salts are effective against borers, termites and fungi (except soft rot fungi), and is widely recognized to be environmentally acceptable and safe for the mammals.

These boron salts are dissolved in water. After treatment, the water evaporates leaving the salts inside the bamboo. Boron salt is non-fixing type, that is, the preservative is leachable. Therefore this process is recommended for bamboo culms that would not be exposed to water or rain.

Borax/boric acid seem to be non toxic to the environment, but is highly saline, and little is known environmental toxicity.
However, as it has a fungicide and insecticide action that suggests it would not be environmentally neutral in case of major pollution.

It is mildly toxic to humans. Simple exposure can cause respiratory and skin irritation; ingestion may cause gastrointestinal distress including nausea, persistent vomiting, abdominal pain, and diarrhea.

There are various way methods of treatment of bamboo.
- Bamboo could be impregnated under pressure in autoclave or by boiling.
- Bamboo could be soak in a solution in an open basin for several days (for slats) until one week if bamboo culms.
- Or by using the “boucherie” method.
However, in all cases, borax/boric acid diffuse better into bamboo when bamboo is moist i.e. in the green condition.

The products made with treated bamboo with borax are not toxic. However treated bamboo must not be burned, as the gases of such a fire are toxic.

There is a debate either the boric acid / borax is toxic or not.

Bassin of Borax solution

Boric acid / borax has low toxicity to humans through ingestion or inhalation. Median lethal dose (LD50) rating of 2,660 mg/kg body mass for man. Boric acid is poisonous if taken internally or inhaled in large quantities. It is generally considered to be not much more toxic than table salt. Some ethnic groups use it however as a food additive. However in some countries it is requested to farmers and restaurateurs not to use it because of unacceptable risk to consumer health.

In France, the boron content should not exceed 1 milligram per litre according to health standard for drinking water.

At high concentrations it is irritating to eyes, skin and respiratory tract where short exposure but may have effects on the kidney in cases of prolonged or repeated exposure.
The European Community decided to amend its classification as repro-toxic category 2 and to apply the risk phrases R60 (may impair fertility) and R61 (may cause harm to the unborn child).

Therefore, if it is said that borax and boric acid is already a more environmentally friendly as well as an efficient way to preserve bamboo, it is sure that it should be used carefully by operators with safety precaution.