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Heat Treating - Post-Soaking


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I need some advice regarding heating strips after soaking and planing.  Because of soaking do the old rules for time and temp still apply?  It seems to me that with soaked strips a lower temp for a longer period of time would be correct, but what temp. and how long?  (Mark Dyba)

    I dry my strips for a few hours at 125 degrees F with the oven door partially open then Heat treat at 375 degrees F for 12 minuets on blond rods.  Have only made one flamed rod, used 375 degrees F for 7 minuets after drying. (Tony Spezio)

    It's a little difficult to make a generalization, as oven temps vary so much, and a convection oven does a better job of removing moisture than does a radiant oven, and . . .

    In the testing I've done, one thing was clear to me and that is that higher temps drive out more moisture, and higher temps for longer times will drive out the most. One would think that 2 hours at 225°F would remove all moisture but taint so. By the same token, we might also expect that a higher temperature for a shorter time followed by an hour at 225°F might also have more of the desired effect, but taint so neither. It is the higher temp which does most of the work. Now, we have the concern of too much heat damaging the bamboo but for light trout rods I don't see this as too much of a concern. At what point are we talking about failure? Anyone who takes the rod to 90° perpendicular to the water is asking for problems regardless, particularly if the fish is in close.  Another thing is that soaked strips acclimate to ambient humidity rather quickly. Regardless, leaving the oven door open to facilitate the removal of steam helps the process. This is more effective with a convection oven, though, as mentioned above.  So, in my opinion and observation 360° true makes the cane more brittle. 350°, however, doesn't seem to have this effect, no matter how long the strips are left in the oven. I wouldn't suggest this for a radiant heat oven, but loading the oven prior to startup, and allowing the bundles to heat soak as the temp rises to the desired temp/time, followed by a cool down to 225°, or less, will remove all the moisture your going to get out of the strips. Your total exposure time will be approximately 1.5 hours, depending upon your oven. The fixtures will also help get the heat into the strips quicker and more thoroughly. As long as the temp isn't too high, the exposure using the fixtures isn't a problem.  (Martin-Darrell)

      I am sure you are correct about the convection-style oven doing a more efficient job than the standard, radiant heating version.  And I have only just completed converting mine to  include an  airflow "loop."

      Possibly, we need to do more testing of temps and times, but so far, I have found that my soaked strips do not lose any more weight after being treated at 225 degrees for one hour.

      So, I am assuming that with this regimen, I have removed all the moisture that can be measured.  What puzzles me is that your experience and mine have been so different, and I wonder what might account for that.  What have others found in their efforts to dry out soaked strips?  (Bill Harms)

        Monkeying around with cane and my grain scale I have found that with the cane I have 225 degrees for an hour I no longer see any weight loss from the cane. 

        Now greener cane my require more time. And here in the south that is South Calif. with humidity around 40 percent  the cane regains most of its weight in about 4 weeks. That is for drying. Heat treating is another matter.  (Adam Vigil)

          Yeah, those are the results I have gotten in drying my soaked strips, too.  After heat straightening, initial shaping and perhaps a day of sitting around on my bench, I can reduce their weight no further after an hour in my oven at 225 degrees.  There may be something I'm not considering, but if my strips have lost all the weight they're going to, I don't know what else to say except that they seem dry to me.

          And, yes, heat treating is another matter.  Some do that prior to soaking and heat-straightening, and others wait until after. I do it prior, so I don't know if that would affect the results I've had so far.  (Bill Harms)

            Okay, it seems we may be referring to two different things, and that is merely drying the bamboo, and heat-treating it. Certainly heat-treating also causes a greater loss in weight due to chemical changes within the bamboo,  i.e., volatile oils, etc. Lloyd Cross's treatise on heat-treating and its effects demonstrated this, and this may be from whence the disparities in our observations come. I don't have, and I doubt anyone else does either, a way to verify how much of weight loss I've seen is attributed to solely moisture, and how much to other factors, but I'm sure the higher weight loss seen at higher temps is not solely due to moisture.  (Martin-Darrell)

              Heat treating the cane pass the drying aspect causes a loss in weight which is not moisture. You can smell it when it is cooking. If you can smell it then it is loosing atoms from the cane. It can be oils or fiber or etc. And when the smells change different materials are reaching or have passed their volatile points. What each smell is indicative of is past my nose hair technology. I believe Ralph has a nose for these things.  (Adam Vigil)

        I'm sure there were different variables involved with our testing methods, among other things. None of my test samples were "wet" when I did the testing. They were all at ambient humidity. One thing to bear in mind, my testing is not at all definitive, nor was meant to be, and was merely a basis for thought on future testing.

        Out of the thirteen samples tested, 225°F for 1 hr. was the worst of the lot, consistently, for moisture removal. The second worst was 225°F for 2 hr, consistently. The best of the testing depended upon whether measured as a percentage, or by weight. The difference between the 225° @ 1 hour. and the best, measured as a percentage was 7.5%. When measured by weight the difference was 3.8 g. That's a bit misleading, however, as there was a size differential between the two samples. In this case, the percentage is a more accurate characterization.

        And for those just dying to know, flaming, darkly done, on both sides of the splits, resulted in the most moisture loss, whether measured as a percentage, by weight, and by amount of time used it was the quickest method to employ. Of course, merely flaming as a method of heat-treatment has its own inherent problems that appear later in the rodmaking process.  (Martin-Darrell)

    After the strips are soaked it will take some time for them to loose the moisture that you introduced. Depending on the background humidity in the storage are, perhaps upwards to a week.  There are several ways the time can be reduced:

    • Placing the strips with some type of desiccant
    • Heating them in your oven for several hours
    • Putting them in the hot air duct for your furnace.

    In our winter, the furnace runs about 75% of the time. The air is about 150F and the fan is on continuous. Dries things up quick. Don't get them too dry. Seems like some moisture in the strips is required to make some of the glues hold. I Had two tips delaminate when they were too dry.

    Further, your probably shouldn't "go to final" planing numbers till the strips equalize. There is some expansion that occurs after the strips are heat treated. The expansion will be approximately 2>4% of dimension after treatment.

    After the strips are equalized to the background humidifies, normal treatment times/temp relationships apply.  (Don Anderson)

Rule

Guys who are wet planing and using MD's fixtures to heat treat afterwards; what are you using for times  and how are you doing it?  I am going to try this wet planing and see how it works for me.  (Bret Reiter)

    I'm using 180-200 degrees for 2 hours after roughing wet.  (Winston Binney)

    Binding in the Aluminum jigs and then cooking @ 375 for 15 - 20 minutes.  Your results may vary.  One per customer.  Not valid where regulated by law.  (Brian Creek)

Rule

I have begun an experiment to document the effects of soaking on bamboo strip dimensions.  Two methods will be used in the experiment as well as a control.  Three strips from the butt section of a cane will be used, one strip for each of two methods and a control.  Strips are 50 inches long and sample points will be located at intervals along the strip.  Sample point C will be located on a node.

Method A. 

  1. Measure strip width and thickness at 5 points (a, b, c, d, e).
  2. Soak strip in water for 24 hours. Measure same 5 points.
  3. Air dry for 48 hours and measure same 5 points.
  4. Heat treat at 350 for 30 minutes cool to room temp and measure same 5 points. (no planing).

Method B.

  1. Measure strip width and thickness at 5 points (a, b, c, d, e).
  2. Heat treat at 350 for 30 minutes cool to room temp and measure.
  3. Soak strip in water for 24 hours. Measure same 5 points.
  4. Air dry for 48 hours and measure same 5 points.

Control

  1. Measure strip width and thickness at 5 points (a, b, c, d, e).
  2. 4 days later measure same strip at the 5 points.

Testing - Method A

Step 1 - measure strip dry

Point     Width        Thickness
A            .258             .244
B            .274             .243
C            .265             .245
D            .301             .245
E            .295             .238

Step 2 - soak 24 hours

Point     Width        Thickness
A            .267             .254
B            .283             .253
C            .276             .253
D            .312             .253
E            .311             .248  (Kurt Clement)

Rule

Does anyone out there use their vertical oven to dry their sticks after rough planing (if you soak first)?  If so, what heat and for how long.  (Tom Key)

    Not vertical but horizontal heat strip oven. I dry @ 125F Till I see no more moisture on the small mirror I use at the cap end  that I cock open just a bit. This is enough to let the moisture out.  (Tony Spezio)

    I use a heat gun vertical oven at 375 degrees for 7 minutes with good results.  (Jeff Volner)

Rule

Question for you builders who soak your strips and use a heat gun oven:

Do you use your oven to dry the strips after rough planing before you heat treat?  If so, what is your regiment - what temp and for how long?

I'm 61 years old with the patience of a 3 year old, and when I'm in the building mode I don't want to wait 2-3 days for the strips to dry after roughing.  Seems to me I should be able to dry them in the oven while I'm adjusting my forms for finish planing.  The rebind with the enamel out, stick them back in the oven for cooking.  (Tom Key)

    I see no need for an extra step.  I soak, straighten, soak and then rough.  By the time I'm through roughing my strips are dry enough to final plane.  You can tell.  They dry out pretty quick - but then this is Texas and humidity is often ~6%, the proverbial popcorn f--t.  (Darrol Groth)

    I am in the process of doing just this, right now.  A week ago I soaked a set of strips for 1 day, then straightened and rough planed them wet.  These are oversized strips for a 3-pc rod with bamboo ferrules.  We have a gas furnace with heat registers in the floor.  My regimen is to hang the strips inside a piece of 4" PVC that is standing up over a heat register so it gets hot dry air from the furnace blasted through it.  I normally just hang them overnight, but this time I decided to weigh them and see how much water they lost.   I first weighed them when I put them in the PVC tube. This was the day I straightened them, but the strips had already been drying for 1 to 5 hours.  When I first weighed them, they weighed 554.2 g.  One day later it was 510.9 g.  The next day 499.6 g.  On day 3, 496.6 g, then 494.6 g and 493.5 g on days 4 and 5 respectively.  It looks like they finally stabilized on day 5.  This morning is day 6 and it looks like they added 0.5 g since yesterday, but then the heat has been off for a couple of hours.

    I'm ready to heat treat today.  I plan on weighing them afterward and tracking the moisture gain - if I have the patience.  In my opinion, the problem with rushing things is that the thread will become loose as you drive off all that water.  Because I straighten the strips wet, I believe that they never get over 212 degrees.  If you hang the strips loose in the oven and take the oven up to over 212 degrees to drive off all the moisture, that will probably allow the nodes to pop up and the kinks to return before you bind them for heat treating.  That may not be a problem if you bind tight enough for heat treating.  I hope this helps.  (Robert Kope)

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