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How to cure bamboo

Bamboo Treatment

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:

How to cure bamboo

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.

How to cure bamboo

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.

How to cure bamboo

The thicker, more mature bamboo species ‘pai tong’ and ‘pai hok’ are used for structural columns and beams.

How to cure bamboo

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.

How to cure bamboo

This is to longitudinally penetrate the bamboo’s nodal diaphragms before the natural preservation treatment.

How to cure bamboo

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.

How to cure 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.

How to cure bamboo

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.

How to cure bamboo

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.

Chemical preservation (with or without the help of special equipment) ensures long term protection. Depending upon the method of bamboo treatment, chemical preservatives can impart short term or long term protection.

With a few exceptions, chemical preservatives to protect bamboo against biological attacks and degradation are toxic. Selection and application has to be done with great care to meet performance, environment requirements and safety.

Depending upon the carrier solvents, bamboo preservatives are divided into 2 different categories: Non-fixing and fixing type preservatives. Non-fixing preservatives will leach out the bamboo when exposed to rain. In other words non-fixing type preservatives are NOT suited for outdoor use.

How to cure bamboo

Bamboo Preservation Tank
Photo by: Stéphane Schröder © www.guaduabamboo.com

Non-Fixing Type Preservatives

Non-fixing bamboo preservatives mainly consist of boron salts, which are effective against borers, termites and fungi (except soft rot fungi). These boron salts are dissolved in water. After treatment, the water evaporates leaving the salts inside the bamboo. They are not toxic and can be used for treating bamboo products like baskets, dry containers, etc. which come in contact with food products.

Boric Acid Borax

Curing bamboo with borax and boric acid is the most popular bamboo preservation method (for indoor use) around the world because it is effective and more environmentally friendly than other wood preservatives.

The combination of boric acid and borax in a ratio of 1:1.5 is an alkaline salt called: Disodium octaborate tetrahydrate (Na2B8O13 x 4H2O) and is available in pre-mixed powder form, usually under the commercial names: Tim-Bor or SoluBor, among others.

Disodium octaborate tetrahydrate is a white, odorless, powdered substance that is not flammable, cumbustible, or explosive and has acute low oral and dermal toxicity. The product itself is fire retardant and shows no hazardous decomposition.

This salt, is used as an insecticide and fungicide, and is also effective against fungi and algae. It has an infinite shelf life and is not affected by temperature. Diluted with water, bamboo can be impregnated, submerged or sprayed with this chemical.

When I moved to Newport, Rhode Island, I didn’t expect for my backyard to have enough bamboo to feed a family of pandas. I thought of bamboo really as something that only grows where pandas live i.e. not Rhode Island.

But as it turns out bamboo does grow in Newport, and my backyard does, in fact, have a very thick grove.

See the massive amount of bamboo in this picture from when I first moved in. | MostlyMinted.com

So here are some things I’ve learned:

  • Bamboo grows really, really fast
  • Bamboo makes a great privacy screen
  • Bamboo, if you let it, will overtake your entire yard, grow through the cracks in your deck, and grow into the neighbors yard leading to uncomfortable conversations over the fence
  • If you treat it right, cut bamboo can be very useful. If you don’t treat it right, it rots

In the effort to stop the spread of the bamboo, I’ve trimmed back some of the new sprouts during the summer which quickly rotted away. I was, admittedly, a little disappointed because I had found some other dried pieces in a corner outside that made excellent plant stakes. I had been hoping cutting these back would be my passive path to more free stakes.

Since then, I did some research. Turns out, winter is the ideal time to trim back the bamboo if you want to make something with it. And those baby pieces I was cutting back are less than ideal. You want three to five years of growth.

I also learned there are multiple ways to cure bamboo. Those dead brown pieces that were standing in place in the picture behind me are technically cured. You can cut it down and leave it horizontally or vertically in a cool, dry place to cure. There’s another method where you leave it underwater for weeks. And then there’s fire curing.

I went with fire curing because it speeds the process up quite a bit, seemed like the strongest method, and seemed easy enough to do.

Here’s a look at the basic setup:

How to fire cure bamboo in your backyard. | MostlyMinted.com

It looks like exactly what it sounds like it is. In blog posts I read some people used grills as their heat source, but I went with an open flame in a small portable fire place.

All you have to do is get a fire going, and start slowly running the bamboo through it. The heat will cause the resins in the bamboo to sizzle to the surface making it look shiny. You rub those resins back into the bamboo and that seals it off kind of like a polyurethane coat would.

How to fire cure bamboo in your backyard. | MostlyMinted.com

It’s a heat, rub with rag, repeat, process until the color fades from bright green to a more mat soft green. I ran each rod through the fire twice. They were about 9ft tall each, and I spent about 30 minutes on each one, and started doing two at a time.

They’re currently sitting off the floor in my basement until I need them for a project I have planned for the spring. I compared them to a few I have that I’m just drying out, and the fire cured ones definitely weighed a bit more and seemed a bit less brittle.

This project was definitely easier than some of the other blog posts talking about heat sources made it seem and really just involved a bit of patience. Also, most of the posts seemed to come from off -the-grid, survivalist types which I definitely am not.

I suppose the true test will be when I use them for the project in the spring. For that, I’ll need to be able to get a screw in the top without them splitting. I’ll keep you posted.

Chemical preservation (with or without the help of special equipment) ensures long term protection. Depending upon the method of bamboo treatment, chemical preservatives can impart short term or long term protection.

With a few exceptions, chemical preservatives to protect bamboo against biological attacks and degradation are toxic. Selection and application has to be done with great care to meet performance, environment requirements and safety.

Depending upon the carrier solvents, bamboo preservatives are divided into 2 different categories: Non-fixing and fixing type preservatives. Non-fixing preservatives will leach out the bamboo when exposed to rain. In other words non-fixing type preservatives are NOT suited for outdoor use.

How to cure bamboo

Bamboo Preservation Tank
Photo by: Stéphane Schröder © www.guaduabamboo.com

Non-Fixing Type Preservatives

Non-fixing bamboo preservatives mainly consist of boron salts, which are effective against borers, termites and fungi (except soft rot fungi). These boron salts are dissolved in water. After treatment, the water evaporates leaving the salts inside the bamboo. They are not toxic and can be used for treating bamboo products like baskets, dry containers, etc. which come in contact with food products.

Boric Acid Borax

Curing bamboo with borax and boric acid is the most popular bamboo preservation method (for indoor use) around the world because it is effective and more environmentally friendly than other wood preservatives.

The combination of boric acid and borax in a ratio of 1:1.5 is an alkaline salt called: Disodium octaborate tetrahydrate (Na2B8O13 x 4H2O) and is available in pre-mixed powder form, usually under the commercial names: Tim-Bor or SoluBor, among others.

Disodium octaborate tetrahydrate is a white, odorless, powdered substance that is not flammable, cumbustible, or explosive and has acute low oral and dermal toxicity. The product itself is fire retardant and shows no hazardous decomposition.

This salt, is used as an insecticide and fungicide, and is also effective against fungi and algae. It has an infinite shelf life and is not affected by temperature. Diluted with water, bamboo can be impregnated, submerged or sprayed with this chemical.

Bamboo has been used for such a wide variety of tasks by indigenous peoples around the world. Even in modern society, it is said that over one third of the world uses bamboo in some form.

In the country of Japan, bamboo is so engrained in the culture that the terminology for bamboo has expanded into conversation. Bamboo is not just a plant but a unspoken symbol of a Nation. To the Shinto Priests of old, the hollow space in bamboo is where all the Spirits of nature live.

Before Bamboo can be used for any lasting craft it must be cut and cured. Cutting is best in August or Winter, when the water and resins are down. Summer time will work as well for harvesting, but with a higher chance of cracks or splitting. Any cutting device will work for harvesting bamboo. A folding saw or a hefty knife are my favorites. If cutting with a knife, cut at a 45 degree angle with one swipe to prevent splitting or crushing the bamboo. At this point I would like to remind you to stop, take a minute, think about what it is you want to make. Look for the right piece, listen to the breeze though the grove. Find a area that removing a piece will be of benefit to the stand. And finally show respect and reverence, for it is not only a exceptional natural material, but the spirit of a people.

The pieces are cut, the project is in mind and you are on your way. Now What?? The work begins. Seasoning bamboo is something of an enigma to most people. Personally, I have been working with bamboo and various methods of curing it for years, and still, I learn something new each harvest season. The key is to remove the moisture, natural starches and sugars without cracking the bamboo. This may be done with various success rates in the following manner, depending on your geographical area (I.E. temperature and relative humidity). The following are a few methods I have played with over the years.

1. SOAKING: A method commonly used in India is to soak bamboo for ninety days in water. Then set to dry in a sunny area for two weeks. I have tried this technique, but only with limited success, due to the extreme heat during Arizona summers. I have yet to try the same method during the winter season.

2. AIR DRYING: Cut the bamboo leaving the branches and leafs still attached. Store the bamboo upright in the sun for two weeks. Then continue drying in a cool dry place out of direct sunlight, cross your fingers and hope for the best. Depending on the area, watch for molding.

3. ABURANUKI: The Japanese method of drying used by the Shaku hachi or flute makers of Japan.
The oils are removed from green bamboo by heating over a charcoal fire at aproximately 120 degrees C. Thereby, driving the resin to the surface which is then wiped off. The bamboo will change color to a lighter green or a yellowish tint. This method is tried and true. I have had very few pieces crack when using this technique, and no insect or mold problems. The bamboo is then set aside to dry for two more weeks.

I would like to note that most Take Shokunin or Bamboo Craftsmen will set aside their bamboo for two to three years to cure out before using. My personal drying time is much faster. The reason . . . . well, simply put, “I live in a desert, not on a humid island.”

What to do now? Say we have a perfectly seasoned piece of bamboo and we are to set off on the adventure of creating your bamboo masterpiece. There are a few things you need to know about working bamboo.

1. Make a pre-cut with a sharp blade before any sawing. This will prevent fibers from splintering during the cutting process.

2. If you need to make holes in your project, you are much better off burning the holes through. The bamboo seems less likely to split during the drilling or later.

Now that you have completed your bamboo masterpiece, what now? You will need to use some kind of finish for your project. The traditional heat and grease works well. Just lightly heat the piece over coals just until it’s warm, then liberally apply oil, grease or fat to the piece. At no point should the bamboo become too hot to hold bare handed.

Other methods include the use of modern sealers. Now, to stay primitive there is one excellent sealer I would use: natural shellac. You say, “What, shellac is primitive?” Well yes, used from the times of ancient Egypt . Shellac is nontoxic, food safe, water proof and will last for years. I currently use purchased shellac flakes dissolved in alcohol. If there is anyone out there that has more information on the primitive manufacturing or use of shellac, please send me the info.

E-mail your comments to “Jason Hawk” at [email protected]

We hope the information on the PrimitiveWays website is both instructional and enjoyable. Understand that no warranty or guarantee is included. We expect adults to act responsibly and children to be supervised by a responsible adult. If you use the information on this site to create your own projects or if you try techniques described on PrimitiveWays, behave in accordance with applicable laws, and think about the sustainability of natural resources. Using tools or techniques described on PrimitiveWays can be dangerous with exposure to heavy, sharp or pointed objects, fire, stone tools and hazards present in outdoor settings. Without proper care and caution, or if done incorrectly, there is a risk of property damage, personal injury or even death. So, be advised: Anyone using any information provided on the PrimitiveWays website assumes responsibility for using proper care and caution to protect property, the life, health and safety of himself or herself and all others. He or she expressly assumes all risk of harm or damage to all persons or property proximately caused by the use of this information.

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.

How to cure bamboo

Drying Guadua Bamboo Poles Vertically in Colombia
Photo by: Stéphane Schröder © www.guaduabamboo.com

How to Dry Bamboo Poles?

The most common way to dry bamboo for commercial purposes is “air drying”. Once the bamboo poles are harvested and chemically treated, all poles should be stacked and stored under cover.

Important factors when drying bamboo:

How to cure bamboo

How to cure bamboo

It is most important to keep the culms away from direct soil contact to prevent fungal or insects-attacks and to avoid the humidity of the soil affecting the drying process.

It is recommended that only mature bamboo culms (over 3 years) are used to avoid collapsing of the bamboo poles, due to excessive and non-uniform shrink-age of the culm.

Remove infected culms from the storage area.

Avoid rapid changes in moisture content, for example by drying round bamboo in direct sunlight for a prolonged time. This can cause cracks in the bamboo poles. Split bamboos do not pose any problems and can be dried in the open sun.

Provide good ventilation (air circulation).

Vertical stacking gives faster drying and less chances of fungal attack. However, a good support system should be in place to avoid the poles from bending.

Horizontal stacking is generally preferred for large stacks. Stacking should be done on raised platforms, or placed on a thick plastic sheet to avoid soil contact. Use separators between each row of bamboo for better air circulation. The culms at the bottom of the stack may crack or bend due to the weight of a stack, therefore don’t pile up the bamboo poles too high.

For uniform drying, the bamboo poles should be rotated in the longitudinal direction every 15 days.

Air drying round bamboo takes about 6-12 weeks. Drying time depends on:

Initial moisture content

Bamboo wall thickness

Quantity of solar radiation

The absence or presence of rain

Speed of the surrounding air

Other Methods to Dry and Store Bamboo

* 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.

Vertical Soak Diffussion for Bamboo Conservation

Environmental

Bamboo Foundation

* Note:
This excellent document is converted from a PDF document

from the www.bamboocentral.org
website.
This was done due to the

PDF causing my PC to hang and space issues. For the complete and exceptional PDF document please visit there website. No information has been altered. The Environmental Bamboo Foundation (EBF) is an Indonesian non-profit organization started in 1993 by designer and environmentalist, LINDA GARLAND.

The EBF strives to protect tropical forests by promoting and demonstrating the many conservation and development opportunities that bamboo offers. The mission of the Environmental Bamboo Foundation is to encourage, through research and education, the sustainable planting and utilization of bamboo in an effort to promote its many environmental benefits and protect the world’s remaining tropical forests and mangroves.

Based in Bali, Indonesia, the EBF has affiliate non-profit organizations in the United States and in Holland.

Acknowledgements

Initial research on modified Boucherie Teatment was done by Prof. Dr. W. Liese, Universität Hamburg, Germany, and later adapted by the Environmental Bamboo Foundation with Don Longuevan under a grant from IESC International Executives Service Corp. Laboratory testing was performed by Koppers-Hickson in New Zealand.

We thank Ben Brown of Mangrove Action Project for providing valuable help and insight during the testing period and providing translation services for the Indonesian edition.

We appreciate the advise/comments made by Prof.Liese along the development of the VSD treatment.

Many thanks to Emerald Starr of Sacred Mountain Sanctuary in Sideman, Bali, who used a high percentage of experimental VSD treated bamboo timbers when building his resort. Seven years later, the bamboo he used is still in excellent condition.

Research &
Development:
Environmental Bamboo Foundation (EBF)
Graphics & Layout: Studio LaBel, Hedi LaBel
Engineering
Consultant:
Ben Brown
Editorial Assistant: Petra Schneider
Project Manager: Ketut Sadia

Every effort has been made to ensure that all the information in this booklet is accurate. However, due to differing conditions, kind and age of the bamboos, tools, and individual skills, the publisher cannot be responsible for any injuries, losses, and other damages that may result from the use of the information of this booklet.