Tuesday, September 05, 2017

Tiki build-along, pt. 9

So, bamboo. I've posted quite a few of these build-alongs thus far, but have not yet spoken about bamboo in any great length. In light of that, you may consider this something of an interlude. I don't actually build anything here, but I do show some of the prep work that goes into preparing bamboo for use in tik bar construction.

First up, get some bamboo. I know, right? I don't have any bamboo at my house (yet). Some day I shall plant clumping bamboo as part of my tropical landscaping, but I'm not there yet. It must be clumping bamboo, because running bamboo is hyper-invasive and, for the most part, seems the more cold-tolerant. Which means you'll never get rid of it once planted and eventually live in a panda habitat. That said, there are a couple of patches near me where I harvest bamboo on occasion. From what I can tell, it's Golden bamboo, a moderate-sized plant that is a runner, and therefore invasive. Fortunately, it's contained by roads and rock and can't bust out of the location. Yay! This type of bamboo can grow to nearly 4" thick under ideal conditions, but around here, I've never seen it get much beyond 2", so no load-bearing timbers. From what I've seen online, older culms are preferred, as they have thicker walls and greater strength/durability. Younger culms might seem just as tall and wide, but the thickness of their wood isn't there yet. The trick is to harvest those clums that are 4-5 years old. Unfortunately, I've not quite figured out how to determine that reliably.

Here's something else to keep in mind: Bamboo is full of water. It's not going to drip on you when you cut it, but the cells are full of the wet stuff, just like fresh-cut wood, so to get it in usable condition it needs to dry out to prevent mold and rot. That's why bamboo FAQs online say to wait until after the monsoon season (in the tropics) or winter (when it goes dormant) to harvest bamboo--less water in the culms. When I started messing with bamboo, I didn't know much at all. So some pieces I set aside to dry without doing anything else. I've since learned that you want to flame-treat fresh bamboo first, and then let it dry. You can tell old, dry bamboo from it's pale yellow color. It's also fairly light in weight due to water loss.

The culm above is dry, but not completely so. It's hard to explain the difference, but there's a slight heft to the wood, and the color is more yellow than washed out. Flame-treating this one resulted in a decent finished pole with good color. But I've learned that it's much more difficult getting a good burn on an old, dry culm than a fresh, green one.

This one was very dry. I'm not sure the story on this one--maybe it was already dying when I cut it, or maybe it was in a pre-cut batch I picked up back in the spring from a Craig's List ad. Regardless, it was light in weight and drained of almost all color. Not a good place to start.

This is why. With green bamboo, there are dramatic color changes to help guide you and let you know when the flame-treatment is complete. With dried bamboo, there's no color change apart from charring. There's also little resin to boil to the surface. The result is a bamboo pole that's more likely than not to scorch.

The end result is also duller than other bamboo, with little in the way of rich, warm colors. It's hard to tell in these online photos, but trust me, if I showed you in person, the difference would be obvious.

So, why did I mess with those two old poles? Because they'd been sitting around for a long time and needed to be flame-treated before they rotted and became worthless. Basically, I was faced with "Fix these now or toss them into the trash heap." I can't afford to waste anything in my tiki bar build, so I treated them. Simple as that. But with those two out of the way, I could turn my attention to greener culms.

I can do a lot with 1" to 2" culms, which are the most common I get to work with. Heavy and dense makes me smile. They'll have a thick wall and be robust, durable. I got this one from a construction area around the beginning of August, before it was bulldozed. Not the best time to harvest, but I didn't want to see this nice one lost. The green isn't quite as bright as it was when I cut it down, but it's still fresh-looking. This culm was a big one--I was able to cut it into three 8' segments after it came down, with the tapered end still 3/4" thick. Not too shabby!

I use a simple, hand-held butane torch on bamboo. The flame-treatment does several things. First, it boils off some of the water in the wood. Not a lot, but those bamboo segments are air-tight, and if you get it hot enough, the pressure can cause the thinner-walled joints to burst. Ask me how I know. To avoid this, you can either punch holes through the nodes with rebar, or use a tiny drill bit to poke little holes through the culm wall near the nodes. Steam will billow out either way. The second thing heat does is harden the bamboo. Bamboo can be worked into different shapes using heat and pressure, but once it cools, the bamboo hardens in that position and loses its flexibility. Thirdly, the heat brings the natural resins within the bamboo to the surface. The resin is visible as white droplets in the image below. Wipe this down with a cloth to spread it evenly over the bamboo, and you've got a natural weatherproofing agent. This protective coating will wear away over time, but it still gives the bamboo a glossy, rich look, regardless.

The main reason I like working with green bamboo is that the color change is so dramatic. The first time I burned bamboo, I was so worried I'd overdo it that I only turned it an olive drab color and thought I was done. Nope, only about halfway there. When it turns olive drab, that's when the resin starts boiling up. Burn it more, and you'll get an abrupt color change to tan. It is abrupt and dramatic--there's no intermediary steps here. One moment a section is green, then poof it's tan. And this happens in weird, connected segments. It's almost pixellated, as if this is some obscure Atari video game from the 1980s. Pop! Pop! Pop! Change the colors of the bamboo from green to tan! It's fascinating to watch, and if you follow the color change, pretty much impossible to not flame the bamboo correctly.

When the color change happens, a lot more resin comes to the surface. When I burn bamboo, I do a single node at a time, brushing the flame over the wood in steady, deliberate strokes. Lingering will result in burned spots. After I achieve color change, I'll do a few more strokes over the node to get a darker color for contrast.

Here's something else I haven't seen mentioned online: Toasted bamboo smells great! That's not something I expected. I don't know if it's the resin or the wood or whatever, but when heated, it has this rich, savory aroma that reminds me of hot dogs and baseball in the late spring. How weirdly specific is that? I like it very much. Alas, the same can't be said of the dry bamboo culms--those just smell like charred grass. Not terribly appealing.

The end result is a rich, glossy pole that can be cut to suit for a wide array of projects and/or decorative uses. Some of which I will share in the not-too-distant-future.

And once those green culms are successfully heat treated, they still need to dry. They need to be stored out of the sun, away from moisture so they'll cure and ensure long-term durability. Bamboo poles 8'-9' long aren't terribly easy to store out of the way, so I went up. I used a few pieces of PVC pipe and fittings hung from the garage ceiling with rope to form a kind of rack, and piled the bamboo there. Voila! Instant bamboo drying space, up and out of the way until such a point in time where I need it.

Here's one more thing about flame-treating bamboo: I find it relaxing. That's not something I would've expected. It's slow going, and not terribly productive work. I've burned myself a couple of times. Normally I set the bamboo on saw horses and work on them that way, but when the saw horses are otherwise occupied (as they are now) I'll either use a chair or just hold them by hand. Either way, I've found that I can just zone out when I'm going this, let the higher functions of my brain go into standby mode and let inertia take over. It's almost a meditative state, which is, again, not something I'd have expected. With the stress of Hurricane Harvey and some other life challenges coming my way of late, I've been in need of such an escape. Fortunately, I've had a stack of bamboo waiting for just such an occasion.

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1 comment:

  1. I've got a stand of bamboo in my backyard if you ever want to come harvest some. It may be the Oldham variety, I can't remember. The stand is 10+ years old.

    Might bwe able to bring some to a common convention if the timing is right.