Bamboo, renowned for its strength and eco-friendliness, often faces a formidable adversary: insects and fungi. Despite its resilience, these pests can compromise its durability over time. However, there exists a simple yet effective solution to bolster bamboo's longevity and sturdiness. In this article, we unveil the Vertical Soak Diffusion (VSD) method—a budget-friendly approach that ensures your bamboo projects stand the test of time.
In VSD, simplicity meets effectiveness. With minimal equipment and investment, you can significantly enhance the durability of bamboo poles. Picture a process akin to infusing a life-saving elixir into the very core of each bamboo segment. By puncturing the nodes and saturating the poles with a preservative solution, you create a shield against the ravages of time and pests alike.
Step 1: Preparing the Bamboo
Before we start the process of treating bamboo, it's important to properly prepare the bamboo poles for treatment. It's crucial to select mature bamboo poles that are between 3 to 5 years old, depending on the species. As they age, the bamboo poles harden and become impermeable to the borax-boric acid solution. On the other hand, harvesting young bamboo is not recommended as it's not strong enough for construction.
Inspect the bamboo poles for any cracks and choose only those that are free of cracks or insect damage for treatment. It is best to wash the harvested bamboo poles to eliminate any mold or dust. Ideally, bamboo poles should be treated shortly after they are harvested. However, a short period of stand-curing, or resting the bamboo poles on a stand, can be beneficial as it encourages the natural drying process and aids in reducing the starch content in the bamboo.
Tie the bamboo poles to a stand or table. Using an iron rod, puncture the bamboo nodes or diaphragms, with the exception of the last one. It's essential not to puncture the last node – a mark on the iron rod can help you remember where to stop. After the nodes are punctured, position the bamboo poles vertically and secure them in place.
If you're dealing with longer poles, a scaffold—a temporary structure typically used in construction to support workers—can assist you in reaching the top of the bamboo. Alternatively, you can also place the bamboo poles on a steep hill, securing the bases against potential sliding and filling them from the top with the solution. The image below illustrates the use of scaffolding for handling taller bamboo poles.
By following these initial steps, you're ensuring your bamboo treatment process gets off to a good start. They are now ready to be treated with the borax-boric acid solution.
Step 2: Preparing the Solution
Two ingredients, borax and boric acid, form the heart of this treatment. Commonly found in crop fertilizers, household cleaning products and cosmetics, these substances are low in toxicity and more environmentally friendly compared to other common bamboo preservatives. Moreover, they don't pose a threat to groundwater when disposed of correctly.
Understanding how much preservative solution you need for your bamboo treatment can seem tricky, but it's as simple as calculating the volume of a cylinder - a process you may remember from your school math classes. Let's break it down:
First, measure the length and internal diameter of your bamboo poles. If there's some variation in the dimensions, select a pole of average size for your calculations. Here's a practical example:
Suppose you have four bamboo poles, each with a length of 1500mm (1.5m or 4.9ft) and an average internal diameter of 50mm. This makes the radius 25mm.
The volume of a cylinder is calculated using the following formula:
V = π x r x r x h
Where:
V = volume of the cylinder, in milliliters (cm³);
π = a constant value of approximately 3.14;
r = the radius of the bamboo pole, in cm;
h = the height or length of the bamboo pole, in cm.
Applying these numbers to our formula, we get:
V = 3.14 x (2.5)2 x 150
= 3.14 x 6.25 x 150
= 2943.75 cm3
Given you have four bamboo poles, multiply the volume by four:
= 2943.75 x 4 = 11,775 cm3
Next, convert from cubic millimeters to liters (1 liter = 1,000,000 mm3):
V = 11,775 / 1000 = 11.775 liters
To ensure you have enough solution, prepare about 15 liters, accounting for potential spillage and the fact that the poles will absorb the solution gradually. Now, let's break down the composition of the 15 liters solution. The solution is 90% water, and the remaining 10% is a mix of borax and boric acid at a ratio of 6:4.
Therefore, you need:
90% Water = 13.5 liters
6% Borax = 0.9 liters/kg
4% Boric Acid = 0.6 liters/kg
100% Solution = 15 liters
Safety is paramount. Always wear protective gear such as gloves and goggles when handling borates, as they can cause skin and eye irritation. Keep the solution out of reach of children. Warm the water to help dissolve the borax and boric acid more quickly. Mix everything until the borax-boric crystals are completely dissolved. If you wish to ensure complete penetration of the solution into the bamboo, you can add a red textile dye as an indicator of absorption.
Step 3: Treating your Bamboo
Let's delve into the final steps for bamboo treatment, which include applying the solution and drying the bamboo poles:
Begin by pouring the solution into the bamboo poles. You can do this using a simple funnel and jug, but for larger-scale operations, pumps and hoses may be more efficient. If any leaks are present in the bamboo pole due to holes, these can be repaired using bamboo or wooden pegs.
The borax and boric acid solution is gradually absorbed by the bamboo, removing starch and killing any insects within the poles. This absorption process typically takes between 14 days, depending on the bamboo species. The solution needs to be refilled daily until the indicator dye, if used, permeates the entire wall thickness of the bamboo. If you prefer not to use an indicator dye, testing for borax content may be necessary.
To prevent evaporation, cover the poles with caps or any effective sealing material. Ideally, this entire process should be carried out in a shaded area to minimize the impact of the sun on the bamboo poles and limit solution evaporation.
After about 14 days, puncture the final node using a small punching rod. The leftover solution can then be used to treat many other poles! Subsequently, dry the bamboo under shade to prevent uneven discoloration and cracking. Once fully dried, the bamboo is ready for use in construction.
With these steps completed, your bamboo poles are now ready for use in your creative endeavors! If you’d like to know more about bamboo treatment, propagation, design, and construction, we highly encourage you to join and immerse yourself in one of our online or in-person programs.
This article was originally published here by Bamboo U, a bamboo architecture and design enterprise that focuses on sharing sustainable ways of building. Bamboo courses are available on their campus in Bali, Indonesia, and Online, lead in collaboration with the renowned design firm IBUKU and bamboo experts from around the world. From growing bamboo to treatment methods, bamboo design and model making, engineering, carpentry, and construction: their workshops cover all there is to know about bamboo building and design. Find out more & join a bamboo workshop here.
