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Heat Treating - Flaming

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I have done my fair share of heat treating experiments with cane and maybe I can be of some assistance.

When speaking of "Flaming" cane keep in mind there are several different techniques and they can give very different results. So when flaming cane is mentioned you will receive differing opinions due to each makers experience with the method he uses. Also, "Iron clad" heat treating regimes are only relevant if you have already ran tests to a specific culm. Each culm we have is similar but different and we have no idea what grade of cane another maker has or is using. So giving specific heat treating instructions will vary  in results due to the nature of the material involved.

I always run sample strips to tweak my heat treating depending on how the cane reacts. Some culms need more and others need little. And yes not all culms need heat treating to make a good rod. But that would have to be determined  before the rod was made not after! Keep in mind some culms are not suitable for a rod and will always take a set no matter how much heat treating is done.

To make things more confusing you will hear that flaming a rod will 1. make it stiffer 2. make it softer 3. slow the recovery. The fact is all of the above can be true. If cane is flamed in a methodical slow sweeping motion from end to end and the enamel mildly darkens a stiffer piece of cane results if the correct torch is used. On the other hand if the culm is not a good "stiff one" and the flaming is quick and the enamel is very dark to black, the flaming has little effect on hardening the cane and the stiffness of the cane is primarily due to the nature of the culm. In this case more heat treatment would be necessary. As for flaming causing a slow recovery this can happen if some damage to the power fibers occurred in flaming. The good thing is with the glues being used a good amount of stiffness is being added to the rod and helps with the recovery.

So experiment a little with your heat treatment so you can make the cane the way you want. Remember the cane you have is not the same as the stuff another maker has. So be careful start from a reasonable point and then try to work up to where you want it to be.  (Adam Vigil)

P.S. Ralph Moon uses his nose to tell when his cane is "done". This works great once you have the experience. I bet his wife uses his nose when making cookies! LOL

I'm on the way to build my first flamed rod.  I already have flamed the culm and doing rough planing at the moment. Now I'm start thinking about heat treating the strips. Is temperature and time different to blonde rods? Can anybody help?

P.S.: What silk will look nice on flamed rod?  (Markus Rohrbach)

For What it is worth Markus, some rodmakers do not heat treat subsequent to flaming, figuring that the flaming does the job.  It may and it may not. I think that you have to make an evaluation of the strip.  After flaming and rough planing, bend a strip severely.  if it springs back to where it was and if it does so in a prompt and lively manner, I would not think additional heat treating is necessary.  If It takes even a moderate set, I would heat a little more.  This is all in the area of experience and If you ask me how far you should bend or how hot you should heat or how long you should flame.  I can't tell you.  Just be prepared to screw up a rod while you are learning.  I think that red silk with no color preserver is pretty classy.  Lots of silk turns too dark or too light, and it is best to make a few test wraps. to avoid disappointment.

Singed. (Ralph Moon)

I just looked back at the text of a test that Adam Vigil did a few years ago where he heated at various temps and times and tested the cane for color, sets, spring, and brittleness. His results suggest that 225 for 1 hr followed by 350 for 30 minutes produced the best results however he did not flame the cane in advance. Is there anyone out there who has done a similar test but with and without flaming prior to heating in an oven? Also for those who soak their strips prior to planing should the heat treatment be done just before taking the cane strips down to their final dimensions - that is before taking off the last few thousandths?  (Larry Puckett)

Here is what I do with unflamed soaked strips.

I soak for five days, this soaks the strips all the way through. Rough bevel a strip and go right to the metal form that is set for finished size. The strip is planed with a starting taper and is left a guesstimate oversize. I would guess about .040 give or take a little bit. The strips are then bound with the small end and a large end together with one pith side out.

My reasoning for that is that the moisture will evaporate better through the pith side than the enamel side. The strips are put in the oven @ 125 degrees F till dry.  I now use MD's fixtures and do the same as above.  The oven door is left slightly open at the top to check for vapor coming out. This is done with a mirror. You will see the vapor on the mirror if it is still coming out. When dry, the sticks are removed and re wrapped with the enamel side out. I heat treat for 12 minuets @ 375 degrees F and get a real nice honey color. If I want a darker rod I go 15 minuets. For the few flamed rods I have made, after drying as above, I heat treat as in Wayne's book. 7 minuets @ 375 degrees F. I am satisfied with the results.

The big thing is try a few strips and do what you are satisfied with.  (Tony Spezio)

When I am doing it the way you mentioned it here I always have the problem that the kinks which I have straightened and pressed reappear. And the following straightening is very critical because of the small dimensions.  Do you have the same problem or how do you avoid it?  (Rainer Jagusch)

I very seldom have any problems with the nodes. I displace the nodes and not smash them.   I do the nodes after the soaking period and go right to beveling the strip. The only thing I do to the nodes before soaking is remove the inner node leaving a half moon shape. The outer node is displaced into this recess. I have an article in Power Fibers on this method I use. If you don't have the disk or access to the article let me know.  (Tony Spezio)

Soaking can have two benefits.

1.  Straightening the nodes and bends requires much less heat.

2.  Rough planing the strips after soaking is like cutting butter, although you need to keep your tools and forms cleaned properly or they will rust. The extra moisture in the strips makes them softer and planing is very easy.  The strips do shrink after drying though, so I do not plant them all the way to final dimensions until after drying and heat treating.

Soaking is done in a tube of water to completely submerge the strips.  I usually do six at a time, which is what I can straighten in an evening usually.  I soak for 24  to 48 hours, but there are others who go longer.  Experiment with it - I use 2" PVC pipe with a bottom end cap.  Don't leave the water in the tube after you remove the strips, it will begin smelling very bad in about a week.  Change it between batches, or add a few drops of chlorine bleach.  (Kurt Clement)

All cane is not equal and my test are just a starting point. Flaming a culm has to many technique variables as well as temp variable to make a statement of fact on heat treatment.

For example when I flame a culm I do it as a whole culm and run a large hot flame from end to end rotating the culm on each pass observing color and how much the drying split opens as it is heated. I do not blacken the culm. I watch for a color change and stop when it medium tan and the split is open about 1". No further heat treatment is necessary, unless the strips absorb moisture over time then a drying at low temps is in order.

Others will hit the culm with a hot flame and blacken it then follow it up with heat treatment.

If you flame and are not sure if you need further heat treatment. You can always put it in an oven and check a few minute variables to see if it is done (stiff). It is just like cooking. I mean bamboo is only a grass and some people eat the stuff.  (Adam Vigil)

Thanks for those observations. Yours is the only really "scientific study" of heat treating that I've seen so far. From what I have read on this list, the archives, and books, it appears that most folks flame then heat treat later. Tony is one of the few that I have seen who mostly just heat treat. I suspect that there are some who as you suggest just lame and don't heat treat any further (I'd like to hear from anyone on the list doing only this). I'm leaning towards Tony's method of soaking before planing, then heat treating just before taking it down to the final dimensions. I'm  sure that as I experiment with my own set of conditions, I'll find a mixture that I prefer. In the meantime your tests will serve as starting points - not being lazy, just benefiting from your and the other members experiences. The lack of an oven is what is now holding me back - that's the last project.  (Larry Puckett)

Not having a oven held me back in the beginning. To put together a bazooka type oven is quick and easy. Some tubing and a coupler with some air holes with an adjustable heat gun from www.toolsteal.com is a cheap way to go. I bought a Milwaukee variable gun for around $65. Just monitor the temps and flip. Also remember to use your eyes for color change and nose for smell.  (Adam Vigil)

When I flame a culm, I don't do any further heat treating in the oven, with the exception of heat setting my glue. As I use Nyatex, I heat treat the glued up sections at 235 for 3 hours. I am quite sure that there is some measure of tempering at this  heat and length of exposure. It has been my personal experience that if I flame AND temper at 375 the bamboo becomes brittle and I get a lot of chipping while planing. I also no longer soak my strips as I power bevel. If you are going to soak, you probably should have an oven of some sort to drive the last of the water out of the strips.  (Mike Shay)

Thanks to all who shared their experience. It was very helpful for me.

Here is what I did:

1.    Flaming the culm for a mottled medium to dark brown. The reduction of moisture was 6.4% by weight.

2.    After splitting, rough planing and binding the strips together I heat treated for 10 minutes (Tip) and for 15 minutes (Butt) at 175°C (347 °F)

3.    After this time I checked for steaming moisture with a mirror holding above the ovens door. There was still some steam coming out.  So I decided to cook for another 5 minutes. After this time no more moisture was noticeable. 

The reduction of moisture was again 4.25 % by weight.

In my opinion the strips are locking good and they are also very straight after heat treating.

Going now for final planing.  (Markus Rohrbach)

Now you are thinking. You have learned more about heat treating then many. Good job. Keep in mind some moisture will reenter as you work your cane and a good drying in a hot box maybe in order in the future.  (Adam Vigil)

After the heat treating and resultant dimension loss, you should wait a couple of days depending on the humidity in your area for the strips to regain some of the moisture. The regained moisture will effect the overall dimension of the cane. You can expect about a 4% increase in moisture uptake. Putting them in a lower humidity box will retard the moisture uptake.  But the moisture will eventually find it way through to the finished rod regardless of the coating you use and increase the dimension.  (Don Anderson)

I made quite a few rods with flaming only. I now add about 5 minutes of heat treatment after the strips are rough tapered. It seems to keep the rod from taking a set and gives the rod a livelier feel. I would describe it as  "snappiness," or faster recovery after flexing.  (Jeff Schaeffer)

Does anyone know if MOE,  deflection,  and recovery are the same.. the spring back part of our spring/lever?  (Jerry Foster)

Modulus of Elasticity is defined as the mathematical description of an object or substance's tendency to be deformed when a force is applied to it. The elastic modulus of an object is defined as the slope of its stress-strain curve.  Deflection is defined as the  term to describe the degree to which a construction or structural element bends under a load. An object will recover unless it's MOE has been exceeded during deflection, if I remember my Statics and Strengths of Materials from many, many moons ago.  (Mark Wendt)

Modulus of Elasticity is the same as Elastic Modulus. It's also known as Youngs modulus, E. It is the linear relationship between stress (force per unit area) and strain (relative deformation). Assuming a simple tensile test, deformation is change in length, and relative deformation is the change in length divided by the original length.

Recovery depends on the material itself, the extent to which it was deformed and several other external factors. Materials subjected to deformation within certain limits (below the elastic limit which is very close to the yield stress) will return to their original configuration. The speed with which they return (recovery speed) becomes a mass/spring/damper problem in which the rod iself plays at least a partial role as all three. And other factors such as the line, and air resistance also play a role, quickly making a full engineering understanding of the behavior of a flyrod a Diff. Eq. nightmare.  Basically, the stiffer the material (higher E), and lighter the mass, the quicker the rod will return to equilibrium. --the reason hollow built rods are said to be "snappier."  (Mark Shamburg)

As I mentioned, it was many moons ago when I took that S&S course.  Some of the details are a little fuzzy.  Thanks for expounding.  (Mark Wendt)

The recovery  time is  a function  of the  frequency of  the  natural first-order vibrational mode for the cantilever.  A number of factors enter into this parameter amongst them are the mass of the beam, the length of the beam it's MOE, and the amount of internal and external damping.  There is a very nice engineering demonstration of this PDF file.

If you have Microsoft's media player.  There is a really nice film clip demonstrating the properties of a vibrating cantilever beam.  (Doug Easton)

OK, with that in mind, what are the factors that determine how far  the rod travels after the stop in the casting stroke?

How does the line, (resistive force, inertial force, at different  times) change the dampening of the pure beam.  (Jerry Foster)

It's the taper, the taper, the taper.  (Mark Wendt)

I think this taper stuff is way out of proportion. hee hee.  (Jerry Foster)

I hope this makes sense...

-What are the factors that determine how far the rod travels after the stop in the casting stroke?

Numerous, action of the rod for one, mass of the line, mass of the rod, mass distribution of the rod, stiffness of the rod, air resistance, dampening characteristics of the rod. And that's without even thinking about what all happens BEFORE the stop in the casting stroke.

-How does the line change the dampening of the pure beam?

If you look at the brief time when the loop in the forward cast is moving forward, (start of the forward cast to the point when the leader straightens out) essentially it doesn't affect the dampening of the beam (rod) at all. At that point the line simply acts like a mass. However it is a mass with some kinetic energy as well, but the dampening all comes from the rod itself, air resistance and input from the caster. At the point when the tippet finally straightens out, however, if you have made a bad cast, some of that energy can be sent back up the line to the rod. And while that may not change the dampening characteristics it will certainly effect how the rod eventually recovers to its original straight configuration.  (Mark Shamburg)

I think I read some book of Engineering before which states about elasticities. I remembered that the book said, elasticity against the pressing force is larger than that against the pulling force, for most materials, of-course, in bamboo case too.

I thought that our bamboo rod is showing enamel side out.  This means that almost same dencity of bamboo material is placed on two opposite sides of bend (when a rod is deflected.)

As most of all knows, bamboo material cosists of fibers and pith.  Fibers would resist against the pulling force mainly and pith would resist against the pressing force mainly.

When a rod bends, outer side surface is pulled and the other side is pressed. Why the rod will not be broken there in ordinally usage?  Because of elasticity? Yes, but which elasticity? pulling or pressing?

The stress for pressing is greater than pulling in general.  It may be why the rod would resist against the bending force so that it should not be broken, and it reflexes to the other side in casting.  The pressed side maybe works as a spring.  It is hard to understand like that the stretched fibers shrinks so much like gum band of our pants, though actually it may happen in microscopic view.

If this is true, an important role is played on the inner side of the bend, that is the pressed stress.

Well let's get back to the topics of heating, drying bamboo material. Are we conscious about what we are doing in changing bamboo characteristics by heating and drying?  Why do you heat treat?  Is it to harden fibers? or to harden pith?  Does high temperature hardens the fibers or weakens fibers? How about on pith material?

Some months ago, there was a horroble happening in Japan. Some certified building designer confessed that he had been doing a fake business. He designed less steel bars in concrete buildings and cheated the inspections of goverment structural low.   So many buildings, apartments, hotels were build based on this guy's structural designs and calculations.  Many buildings were abandoned or rebuilt.

Bamboo material could be considered like a concrete building, especially like a pole of concrete which has steel bars inside.  When steel is less inside, the cement would be broken with less force.  But if cement is weak, the pole would easily be bent and would not reflect.

Which MOE value is used in designing a bamboo rod with math?  Pulling? Pressing? or both?   Both means that the MOE is measured using a hexagonal section of a rod as a sample.

etc., etc..  Just for a thought.  (Max Satoh)

About five years ago (when I still enjoyed theorizing about fly rods), I was testing MOE with a simple beam bending apparatus and decided to try to separate the compression and elongation moduli: so I laminated a Tonkin bamboo sample to a piece of spring steel (whose modulus is very consistent) and subjected the composite to either bend or to compress the bamboo.  Now the size was calculated so that the neutral axis always lay entirely in the steel so that the bamboo was either entirely in compression or entirely in tension depending on how it was stressed.  (Milward did complement me on the ingenuity of the approach once.)  To my surprise the difference was less than 10% which was less than my predicted experimental error.  I only did this experiment twice so I don't consider it conclusive. Anyone else find different results?  (Jim Utzerath)

Very interesting observations. But I'm not sure if I follow the logic on your following statement "Both means that the MOE is measured using a hexagonal section of a rod as a sample." My admittedly very limited understanding of how MOE effects a beam or strip of bamboo gives me the impression that the level of MOW, at a certain water content is  static and while it may affect both the pressing and the pulling to different degrees it wouldn't be necessary to calculate both forces separately as the level of MOE couldn't be changed to accommodate both forces simultaneously. It would simply be measured for each apposing piece in calculating a rods action.

Of course, I may be way off  base in my understanding of the process. I would be very interested in hearing more on this from some of the engineers among us. Input anyone?  (Wayne Kifer)

Thank you for response.

How do you think this test as below;

We will prepare two kind of bamboo sample strips of the same size and of square cross section.

1. Bamboo as is, one side surface is enamel and the other side is pith.

2. Glued section,  glue two same size strips with enamel side out.  The thickness of each strip is one half of 1.(and less glue thickness)

Both sample has the same length.

Hang the same weight at the end of each strip and measure the sink.

I am not sure yet what can be known by this but I am interested in knowing how the inner side material affects the bend.  At least, we may know the difference of hardness between pith oriented bamboo and fiber oriented bamboo material.

If we make the sample 1 up and down opposite, it is also interesting.  (Max Satoh)

Not sure what results you would be trying to achieve, since you are kind of comparing apples to oranges.  You are comparing a single strip, with the power fibers concentrated to one side, against a matrix of two strips laminated with an adhesive, adding to the mix, bonded to create a beam.  If you are just comparing the two to see which will bend more, many research scientist have already done that work for us and have determined that the beam will be stiffer in the long axis than the single piece of cane. ;-)

Remember, the closer you get to the centerline of the object that is being bent, the less and less the material contributes to the overall strength of the beam.  The true exact centerline of the beam or single strip will have neither tension or compression forces acting on it.  A beam will always be stiffer in cross section and mass than a single solid piece of material.   (Mark Wendt)