Posts Tagged Bamboo Processing

Curing Bamboo

Our attempts to switch over to agroforestry of bamboo to substitute wood for our handicrafts took me to , and Bangalore, where I had the pleasure of meeting some rare breed of "bamboo connoisseurs". The 5 day seminar offered insights into novel methods of bamboo preservation and product development.

To a layman, bamboo epitomizes "a poor mans timber"- an ambivalent "pole"- being utilized in almost all rural activities- may it be construction, fencing, fishing or agriculture.

Why preserve bamboos?
Natural Untreated Bamboos are classified as GRADE 3 timber material. However, when properly treated it turns out be a very fine timber, in ways, stronger than steel and ALL HARDWOODS. In its treated state- Bamboo is classified as GRADE 1 Timber- along with Sagwan and Sal. Thus, treating bamboo becomes a necessity. 

These techniques include non-chemical and chemical methods, some of which I have already discussed in one of my earlier blogs.

Sap Displacement, smoking, white-washing, storage in water.
Chemical treatment methods (CCA), Boric acid / Borax

Treatment in boiling linseed oil / oleo-thermal process-
I am intrigued by the simplicity and functionality of this process. Where-as, other processes may involve a time span of at least a few months, from the time of harvest to a fully dried and treated bamboo, the oil process renders a ready/treated and duly de-hydrated and de-starched bamboo, in a matter of hours!!! I am trying out various combinations- to study the costs involved, as well as to minimize chemical deterioration and the associated fire hazards

Would appreciate comments/observations on this method


Outer/Exterior Protection

Lacquer vs Varnish- Both lacquer and varnish are used to provide a finish to wooden furniture, but they are different in ingredients and how they are made.
Varnish is made from resins that are mixed with thinners or other solvents to remain liquid. On the other hand, lacquer is made by dissolving cotton and nitrocellulose in solvents.
• Varnish is always transparent, whereas lacquer can be made to give tinted finishes.
• No flattening agent is added in lacquer, whereas varnish can produce semi glossy and even satin finishes because of the presence of flattening agents.
• Lacquer being quick drying, it is applied mostly by spraying whereas varnish is applied using a brush.

Varnish is a resin(natural or synthetic) dissolved in oil and does not contain pigments. It produces hard film. Where as lacquers are quick drying coatings made of nitrocellulose dissolved in solvent with pigment added for color.

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Iron Bamboo Processing and Preservation

As a person undertaking agro-forestry of bamboo, we process Iron Bamboo for Handicrafts, Martial Art or Medieval Replica Weapons for Self Defense, which involves specialized methods and techniques of processing and preservation, to increase its durability.

Preservation techniques-

The empirical wisdom or popular knowledge, of indigenous people, peasants, farmers and artisans, has been developed through centuries in all the continents and has resulted in well-known methods and techniques to effectively preserve bamboo. Traditional methods are generally cheaper to implement and can be done without any special equipment.

For proper Preservation of iron bamboo, it must be harvested/cut early mornings, before sunrise, in winters - on a waning moon.** (This is a controversial topic, scientists argue over the truth behind this “peasant knowledge”. Nevertheless, detailed studies show remarkable differences with untreated bamboo, when harvested at specific hours and moon phases. The starch content is lowest between waning gibbous and last quarter between the 6th and 8th day after full moon due to the higher gravitation of the moon. On the basis of photosynthesis, in the course of the morning, bamboo starts transporting starch from the roots into the leaves.

Soaking- After harvest, bamboo is stored in running water for 3-4 weeks to leach out starch.

Chemical Treatments ( any one -to be done immediately after harvesting or after soaking)-

  • CCA (copper-chrome-arsenic composition, in the proportion 3: 1:4) is good for bamboo, but has associated health hazards. Thus, it has to be used judiciously, if at all. Bamboo products are tanalised, impregnated under pressure or boiled with chromated copper arsenate (CCA) to protect against rot. CCA is effective but toxic/carcinogenic.

  • ACA- Ammoniacal copper arsenate penetration in bamboo is effective against fungi, bacteria and insects. However, ACA is eco-toxic non-degradable.

  • CCB and CCBF  - commercially ASCU.

  • Boric acid, borax and boron are cheaper than CCA and less poisonous. This is used at a concentration of  2.5 per cent each, to be dissolved in hot water. The preservative, (disodium octaborate- which forms as a result of the reaction), is easily soluble in water. This process is only recommended for bamboo culms that would not be exposed to water or rain. 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.

  • Other alternatives methods:Treatment of bamboo with limewater.

  • Drying of bamboo before use is necessary since dry bamboo is stronger and less susceptible to biological degradation than moist bamboo. In some experiments carried out it was found that Acetic acid (Vinegar), completely prevented moulds/fungus incidence during the drying process. (Tang et al., 2009).

  • Following the drying, the bamboo is TRADITIONALLY smoked by storing it above a fireplace, to blacken the culm. This, however, may not be necessary if chemical methods are used.

  • Fire Retardant Preservative- This treatment is intended to protect materials against fire as well as decay and insect attack. A mixture of boric acid / copper sulphate / zinc chloride / sodium dichromate in a ratio of 3:1:5:6 is recommended at 25% for indoor and outdoor use

  • For Termites- 1% Dieldrin may be added to the preservative. However, Dieldrin is dangerous, and use is illegal in several countries.

Further information
• Non poisonous Timber Protection Practical Action Technical Brief
• Designing and Building with Bamboo by Jules J. A. Janssen

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