Under Pressure…using steam to cure bamboo.
At precisely the correct alignment of the moon and sun, the water content in bamboo drops like the tide going out and we, the LEAP Academy, head into the dense Bali foliage in search of rare and wonderfully twisted bamboo.
Our mission is to find a local source of material to design and build artistic, unique and sustainable bicycles. We are working with the Art Bikes Bamboo master, Klaus Volkmann who has joined us from Brazil. We are looking for bamboo of a certain age, diameter, quality, but most importantly…curves. Klaus specializes in stunning and unique bikes that take advantage of the bamboo’s ability to be strong and light but also to have strange and beautiful shapes.
In order to be able to use the bamboo we harvest we need to have it dry and that can take a long time in the rainy season of Bali. Klaus has instructed us on his technique of using steam to dry out bamboo that is still green. After only a few hours the bamboo can be cut and used for building. How can steam dry out the bamboo? Well the steam is the conductor of the heat energy. The heat expands and pushes the water out of the cells of the big chunks of grass (a.k.a bamboo)and lets it escape from the pressure release valve as condensing steam.
We harvested some great bamboo but we were not sure what part of the curves we wanted to use so the model of steamer Klaus uses seemed small for us. We decided to make a double barrel steamer. Leeland a LEAP student also brought in his homemade smoker made of recycled barrels so we thought to experiment with using the smoke and heat to try the same thing.
So on our first smoking the bamboo did get dryer and lighter but we did not have enough fuel, heat or time with the smoke. The heat transfer from one barrel to the other was not sufficient. So we went on with the steamer. Our second attempt looked like a good design. Lots of water to boil in the bottom third of one barrel, a short galvanized pipe connecting the boiler to the double barrel steam chamber and some good rubber innertube seals on the lids and joints to work as gaskets and hold in the heat, steam and pressure.
We drilled a small hole for the steam to release and began by building a fire under the 55 gallon drum. The fire was not getting enough oxygen and we worked hard to fan the flames and finally got an electric fan to keep the water boiling.
It seemed the mass of the water, the area of the double barrel chamber and all the mass of the green bamboo was just too much to heat up with our little fire. It got warm, dried out a bit but we needed more.
We lit a fire directly under the steam chamber and dried it out…well we even burned some that were on the bottom of the barrel in contact with the fire. This gave us an idea. We took the grate from the smoker and it lifted the bamboo up into the middle of the barrel and then tried it again…it worked.
Then we decided to put the barrel on a tilt and put some water directly inside the steam chamber and steam the barrel in the same chamber…another success. When we began the workshop we had plenty of bamboo ready for building our bikes and we would go on to do many more loads during the course. If at first you don’t succeed, try and try again…or in our case…just keep the fire going until it’s dry!
After we selected just the pieces we wanted for our bikes we brought in a large propane gas torch and did the final drying and decorating with fire. This pulls out the last superficial moisture and prepares it for the vegetable resin sealant that we apply before building the bikes. We are ready to take this grass to the next step and bikes building to a whole new level.