Update: Wednesday, May 6, 2009

In this post:
Understanding Bamboo Heat Treating and Bamboo Ovens

The next stage in making a bamboo fly rod is heat treating the bound up sections. As a very general rule, makers tend to heat treat their bamboo at approximately 350 degrees for about 15 minutes. But before I simply threw my strips in an oven and turned on the heat, I want to understand this aspect of the work a little more fully. What I learned was that heat treating bamboo is a science with a mountain of opinion, but very little scientific foundation. Most makers believe that heat treating is important because it removes excess moisture in the cane, retards moisture reentry, relaxes sweeps in the strips, “reprogramming” them to fit neatly together, makes final planing easier, and crispness the feel of the completed rod. “You can just feel it.”

How scientifically verifiable those beliefs are remains a mystery. In an email to me, noted rod-maker Don Andersen summed up his findings on a series of published bamboo heat treating tests by writing, “Chad, I couldn’t find any reason to heat treat, and [when] others replicated my original tests, they found much the same results.” So I asked Don why everyone continues to heat treat and why they recommend it to new rod makers like me. His answer was simple if not satisfying, “Why do we heat treat? Inertia – it has been done that way for years. Why change? I still do it – no idea why. But some day, someone will stumble on the reason.”

Perhaps that makes heat treating bamboo a religion rather than a science. I don’t know. What I do know is that bamboo makers have been heat treating bamboo for a hundred years. It’s not the place of a first-rod maker to change that tradition. So I set out to learn about and eventually build a bamboo oven.

One of the great things about making bamboo fly rods is the way the cottage industry respects ingenuity. This is never more evident than in the realm of bamboo ovens. The various styles of Bamboo ovens tend to be named after the guys that first designed and built them. So, for example, a maker is said to have built his own Cattanach-style oven. The downside is that oven names aren’t very descriptive and similar ovens may have a plethora of names based on minor (albeit important) modifications. So for our purposes, I’m going to talk about three styles of bamboo ovens that I have grouped and named based on their heat source.

A) The Element Oven. These ovens use an element (such as a mica strip) for their heat source and typically embed the element in a rectangular box built out of heating-duct sheet metal. Most commonly, element ovens employ two rectangular sheet-metal boxes. One is an inch or two smaller in overall dimensions and fits inside the larger one. Insulation is then placed between the two boxes in the 1-2” gap. The best of these ovens have programmable thermostats and two chambers: one chamber – the element chamber – contains the heating element; the other chamber – the bamboo chamber – contains a screen on which the sections of bamboo rest for heat treating. A fan circulates the heated air from the element chamber to the bamboo chamber (i.e. convection). This design eliminates possible hot spots and uneven heat treating.

Properly built element ovens that incorporate convection are probably the surest way to evenly heat treat bamboo in a repeatable fashion – rod after rod. Without question, they are the most complicated and expensive. Here’s what Don had to say about his oven, “[Mine has] two 1500 watt electrical elements, recirculating fan, thermostat control. One element is "direct" drive through a switch with the other using the thermostat to control temperatures. Works like a hot damn. Results are consistent and repeatable. Cost is high. I've got about $1,000 invested in the oven.”

I have included a few pictures below to help readers visualize these ovens and understand just how super fancy they can be.

A fan built specifically to handle heat in excess of 300 degrees


The same fan nested in a heating duct to move heated air from the element chamber to the bamboo chamber


The front view of this same oven (element chamber is on the left and bamboo chamber is on the right)


Here is a different element oven that has only one chamber, but a nice programmable thermostat (Note: the tubes on which the heating element is mounted may be heatsinks designed to more even disperse the thermal energy and eliminate hotspots )


B) The Heat-Gun Oven. These ovens use heat guns as their heat source, generally blowing the heated air down into a heating-duct cylinder where the warm air then rises back up through a second cylinder that contains the bamboo. These ovens are simple, effective, and inexpensive (perhaps $50 to build, not including the heat gun, which you need anyway for straightening and flattening nodes.) We will build a heat-gun oven in the next section that incorporates a popular modification. In the meantime, here are a couple of pictures of the standard heat-gun oven design.

Full view of a heat-gun oven


Top view of a heat-gun oven with the heat gun inserted in the heat chamber and the bamboo chamber open


C) The Torch Oven. These ovens use a propane torch as their heat source, playing the torch’s fire over the surface of an iron or aluminum pipe. The bamboo is placed inside the pipe and both ends of the pipe are plugged. One or two small holes are drilled in the surface of the pipe to release pressure and give the maker some indication of how the treatment is progressing. This oven is old-school, seems too simplistic, and is not all that popular today. But consider the comments of maker Ralph Moon…

“I simply cannot convert anyone to retrogress in their thinking on heat treating. I see some of the ovens available and I, too, begin to salivate. But the fact remains that if you want repeatable results rod after rod. Results with virtually all of the ambient moisture expelled, uniform color of the cane; no matter what the temperature of the shop may be, no matter what the humidity may be you have to go back to basics. Forget the stainless steel sheet metal, forget the intricate and often costly heating elements, forget the forced air heating, forget programmable thermostats, heat sinks, shielding and flipping end to end, and complex timing formulas. It takes an engineer to do all of those things and I would rather build rods. I explained my technique in Power Fibers, but basically it requires two clothes hangers, five feet of iron pipe, two wooden plugs and a propane torch. Pop the strips in the pipe, pop in the plugs, use the coat hangers to suspend the rod at a decent height, and pass the propane torch back and forth rotating the pipe 1/4 turn after each pass of the torch. The rod is done when the steam exiting from a small hole in the pipe stops and the odor of volatile oils commences. Go no further. You are done. Just remember the smell and you can duplicate the results time after time.”

We will also build one of these ovens in the next section, so you will have to wait for the pictures.