Questioning and Understanding Conventional Wisdom

[A Random User]

It is often said one should do work on a juniper when they are dry.
Meaning, have not been watered in a little while. The logic behind this reasoning is the following... when a tree is dry, it's cambium layer is less likely to separate from the heartwood or pith... the center part of a branch or trunk, the part that gives the branch or trunk structure, where one often is able to count rings.

Now, this makes sense... however, for me, what I have found through doing endless amounts of bending and perhaps this has a lot to do with my climate... is that what usually ends up happening when working on material that is dry, is that the pith or heartwood, ends up breaking more violently than that of material that is not dry, and thus is more likely to cause separation of the cambium layer and loss, do to the sudden act of it snapping.

I will give you an example... if one picks up a twig off of a forest floor, and tries to break it in half. What they will normally find is that a dry twig will easily snap... a green or wet twig will not, and in fact one needs to often pull it in varying directions just to try a tear the branch apart. Seeing that the cambium layer usually will easily peel, it is not this that is holding the branch together, but the structure of the twig, the pith or hardwood.

Let me step back for a minute and explain what actually happens when a bend is preformed. In a bend, the cambium layer is soft and pliable it easily does the bend. The structure, the pith or heartwood, is not... What happens in a bend of any significant degree, the pith or heartwood, actually splits and separates, usually right down the middle, in the opposite direction of the bend... so if one is bending a branch down... the split will occur on the side of the branch, and will run parallel along the length of the branch. The center of the pith is the hardest, and thus the most fragile when it comes to being flexible. Thus why this is the first place to break.

In doing a bend of any degree, this is what one wants to happen... we want and need the split to happen, in order for us to set the branch. Easiest way to visualize, is if one thinks about, or has ever had the misfortune of breaking a bone and having to have it reset. We are in essence breaking the bone of the tree in the process of bending and holding the branch in place until it resets.

Why do we want this to happen?
Let, me say that it happens regardless of whether or not we want it to in a bend of any degree, it is just that if done right, the cambium layer is not disturbed, and from all appearances it appears to not of happened, cause we cannot see inside the branch.

So, really the question should be... How does this split help in what we are trying to perform? It helps, because the split in the pith allows the two parts to more easily slide over one another to make the bend. The two pieces, no longer have the strength they did, seeing that the hardest part, the very center, now has been see rated into two.

On a very old branch or heavy one, that one wants to do an extreme bend in... one will often go ahead and actually induce this split with your branch splitter, to make the separation. Giving the branch more pliability and to help prevent that of the alternative, a violent break. With this procedure one is in essence doing a controlled break. Allowing for better control over how and what damage is done in the process.

With a procedure such as this, I think it needs to be said, that careful planing should be considered in doing it... especially in regards to direction one make a split... Very Important! If one wants to induce a split, consider the direction one wants to bend. If you want to bend down or up, you must split on the side of the branch, or horizontal... If one wants to bend side to side, the split should occur from top to bottom, or vertical. Reason? You want the split to slide over each other and stay together, not the alternative, the split opening up. This will allow for the cambium layers to align, heal up and the eventual healing of the wound. Enough, about that! Just felt it was the responsible thing to go into some important details so as to not have folks possibly trying a technique such as this, and ending up with an abomination.

So, back to bending...
This is why we use wire, raffia, etc. If the pith or heartwood, splits naturally when bent, we want to control the outer section of the pith that has separated, and that has to make the longest journey to do the bend, to actually be supported, as to not completely break and separate coming through the cambium layer, but instead tear along itself length wise.

Often where this fails is through lack of this support... which occurs in a number of ways.
Them being no support at all, lack of sufficient support as in the support was not strong enough to do the job of holding, the support was put on inefficient as in to loose of wire or raffia, or the actual bend was done in a spot where the support was the least strongest.... which nine times out of ten is the case. Where the bend was performed in a spot where the wire that was put on to actually support, ended up being wrapped on the inside of the bend and not the outside, which had the farthest journey to make to complete the bend.

What to do if a break occurs? Often just because this happens, does not mean all is lost. Secure the branch in place with further wire, so the effected area can remain un-moved and have time to heal, and add some cut paste or covering to allow the area not to dry out.

Lastly, I wanted to go back to the beginning of this thread and speak about Cambium layer separation from the pith or heartwood. .. where this 9 times out of ten occurs is when one bends in one direction, then decides to bend the same area in the other direction... I know it is hard, trying to visualize where one needs to place a branch or trunk, especially if one is newer to doing bends, but one needs to try and visualize as best as possible where they want to go with something, before going with something... If you are having a hard time doing so, get out a piece of paper and draw what you would like to see. Erase if you have to...

The logic or lack of logic, which ever you prefer, that I have expressed here was stated with the notion of working on Junipers... obviously, it goes as well with any type of material.

 

[Robert E Holt]

Very good description. I find this sort of instruction helpful in learning how to style bonsai. It is a little unclear in the discussion on inducing a split to aid in bending. Some pictures of the two types of splits and bends would be helpful, especially if you could show the results if done correctly vs the results if it is done incorrectly.

Thanks!

 

[M. Frary]

Nice explanation of what's going on when a limb is bent.
I myself have learned the hard way about bending the limb in one direction and leaving it or knowing which way I was going to bend it beforehand.

 

[A Random User]

Very good description. I find this sort of instruction helpful in learning how to style bonsai. It is a little unclear in the discussion on inducing a split to aid in bending. Some pictures of the two types of splits and bends would be helpful, especially if you could show the results if done correctly vs the results if it is done incorrectly.

Thanks!

Sorry, this is my bad... I have folks coming over to stay with us this week and was extremely busy, cleaning up and in the middle if this trying to compose this thread, while taking breaks... so yeah, reading over it now, it is a little disjointed.

Here are the points I was trying to make...

1. Questioning of conventional belief.
I have found the opposite to be true through continually doing the practice of bending in all types of different procedures. That the cambium layer that seems to be the reason of concern, is actually effected in just the opposite way. That it is not the cambium layer that I see wants to separate, but rather it is through the force of how the pith or heartwood breaks that causes the force in separation.

2. The pith or heartwood breaks totally different depending on whether it is dry or wet. The dryer it is, the more force.

3. I wanted to explain what happens when one does a bend, and how the different layers react. As well try and examine how this reaction if better understood could actually be used to one's advantage.

4. Give an example of this advantage... which was the splitting method... there are plenty of more ways and procedures as well. Here for me is where some if the problem lies with my post. How am I to tell one about a procedure, and not give at least a bit of insight into doing it... This is where the post took a right turn and got lost... however I could not have folks trying something with a least a couple of facts regarding the procedure. I think this would be irresponsible.

5. I wanted to briefly go over common failures that are going to sometimes happen when doing a bend.

So, I probably should not have included in the discussion the induced split technique, however if I did not yet said there are ways of inducing a split, I would have been asked, what are they.

Now, since you have inquired about the technique... I will explain it perhaps in this way... Say you have a sandwich, I know... it sounds funny, but seeing it has layers and is easily identified, I will role with it!

So, if you have a sandwich, if one holds it up where one can see the profile, or side, with all the layers of what is inside, if you take both sides of the sandwich in each hand and fold them down, with your thumbs pushing up in the middle, the different layers of what is inside all fold together to form the arch.
Now, if you return the sandwich back and this time try and fold it back away from you, one will find the layers will want to separate, and in fact the middle will want to open up. You don't want your sandwich opening up, or you will drop all its ingredients on the floor! Hope this helps... if not, will try and get some illustrations or pics up soon!

 

[Robert E Holt]

I get the separation part and yes the sandwich analogy does help visualize the discussion. The vertical split I think i can understand. You split the trunk (or branch) along the grain of the wood, thus separating the fibers so that when you bend them the branch is more flexible. One of the issues with bending (from an engineering perspective) is that the fibers on the inside of the bend travel a short distance (in fact they go into compression) while those on the outside are forced to travel a longer distance. This causes a separation, which doesn't always occur where or how you want. If you induce a split prior to bending, the outside fibers have more freedom to move and you have more control (right?). I guess the part I was confused about was; "If you want to bend down or up, you must split on the side of the branch, or horizontal..." . Would not a "Horizontal Split" be a break?

 

[A Random User]

I get the separation part and yes the sandwich analogy does help visualize the discussion. The vertical split I think i can understand. You split the trunk (or branch) along the grain of the wood, thus separating the fibers so that when you bend them the branch is more flexible. One of the issues with bending (from an engineering perspective) is that the fibers on the inside of the bend travel a short distance (in fact they go into compression) while those on the outside are forced to travel a longer distance. This causes a separation, which doesn't always occur where or how you want. If you induce a split prior to bending, the outside fibers have more freedom to move and you have more control (right?). I guess the part I was confused about was; "If you want to bend down or up, you must split on the side of the branch, or horizontal..." . Would not a "Horizontal Split" be a break?

Awesome... you are now talking my language! Yes a horizontal split would be a break... see, where I was going with this, is that this is in fact what actually occurs anyways within the branch when one does a bend of any degree, you just cannot see it.

If one is bending up or down, you want this kind of break to occur, a Horizontal break along the grain, you just do not want this Horizontal break to transfer to a Vertical across the grain. When this occurs, which obviously will be on the outside of the bend, the damage is transfered to the cambium layer.

If one is wanting to bend left to right you would induce the split in the opposite direction... Vertical, along the grain, which here again is what would naturally occur if one was to do a heavy bend left or right. In this case you do not want the break to occur Horizontal across the grain.

If one splits the wrong side of the branch depending on which direction they are bending, they are in essence, splitting across the grain. Thus, when bent the split will open up.

As far as the separation of the cambium layer from the heartwood discussion is concerned... it is my observation and argument, that usually where this occurs is not from doing the heavy bend itself, but from the transfer of energy contained in the bend itself, failing... causing a break across the grain. This is where I see the damage being done There is tons of energy being stored within the bend... when a break occurs, it releases this energy. While doing so, it moves the heartwood back n forth like a shock wave, if you will... this back n forth motion is where I am proposing the separation of the cambium layer from the heartwood occurs... not in the bend itself.

When ever I have ever had a loss as a direct result of a bend, it has always been when some type of back n forth motion has occurred. Either through a severe break... or a bending in one direction, then a reversal of this bend in the opposite direction.

Now, I have had breaks that have occurred while the branch or trunk was wrapped in raffia and even wire, that I believe because of them being wrapped, minimalized the impact of the break, so the transfer of energy from the bend failing, was not as severe... in almost everyone of these instances there was no loss.

 

[Robert E Holt]

OK, I think I see my misunderstanding. When you referee to "vertical" or "horizontal" split, you were really referring to which side of the trunk/branch to perform the split. If bending left of right, the vertical split would be made on the front/back of the trunk and if bending front or back, the vertical split would be on the left/right of the trunk. In both cases you are splitting with the grain, in effect you are sepperating the grain so that it will bend easier.

What tools do you use to split the trunk?

 

[A Random User]

This is why I am proposing the idea of questioning conventional wisdom... it is my observations that "Wet" wood is less likely to break than "Dry". That in fact, usually "Wet" wood is more likely to tear along the grains, and not across.

That the separation of cambium layers from the heartwood does not occur from the bend, but instead from a fail in the bend and the energy of the bend being transfered throughout the different layers... causing a back n forth motion.

I am not just throwing this out to disagree with conventional wisdom... I think it is an all actuality a legitimate proposal based on first hand accounts of what I see happening. I think it is a subject worth considerable debate... it could change alot of how we understand and work in bonsai. Every time on does a bend, even a slight one, i think if they better understood the properties at work, they would be better armed with information of how to do the bend and less likely to have loss in doing so.Would love to here any opposing views as well. Perhaps there is something I don't understand, or are missing? Just trying to learn, understand, and question what I am doing.

 

[Robert E Holt]

Now that I better understand the proposition, I agree with you.

I also do a fair amount of woodworking. When I go to bend a peice of wood, the last thing I want is for the wood to be dry. In fact, typically the wood is heated and steamed to ensure it is more flexible. In Bonsai we certainly can't steam the branch or trunk prior to a bend, but the wetter it is the more flexible it will be making it easier to bend without breaking.

 

[A Random User]

OK, I think I see my misunderstanding. When you referee to "vertical" or "horizontal" split, you were really referring to which side of the trunk/branch to perform the split. If bending left of right, the vertical split would be made on the front/back of the trunk and if bending front or back, the vertical split would be on the left/right of the trunk. In both cases you are splitting with the grain, in effect you are sepperating the grain so that it will bend easier.

What tools do you use to split the trunk?

Yes, which ever direction one wants to bend you need to split with and not across the grain. It would be as if you ripped a board down the middle and tried to bend two boards.
I use a trunk splitter for most material.
For extremely large, one might have to use a saw. The split i induce is usually very small, about an inch... all one is trying to do, is induce a kind of score line, so when one does the bend, it continues to break in the direction one wants it to.

 

[Robert E Holt]

Yes, I see that. The split separates the fibers so that they can slide as you make the bend. The fibers only travel as far as they need to depending on where they are on the bend.

 

[jk_lewis]

perhaps this has a lot to do with my climate...

Which is what? You say nothing about where you're from. Pls amend your profile.

 

[A Random User]

Now that I better understand the proposition, I agree with you.

I also do a fair amount of woodworking. When I go to bend a peice of wood, the last thing I want is for the wood to be dry. In fact, typically the wood is heated and steamed to ensure it is more flexible. In Bonsai we certainly can't steam the branch or trunk prior to a bend, but the wetter it is the more flexible it will be making it easier to bend without breaking.

This is my view as well... I live in a very wet climate. I do work on trees that always are wet because of this... have not had any issues. In fact, quite the opposite, anytime I have ever broken a branch or had a loss due to a bend is either been from my own errors of not proper preparation, in the form of wire not being right, or no raffia, or improper applied raffia,etc. Or material being dry.

 

[A Random User]

Which is what? You say nothing about where you're from. Pls amend your profile.

Thanks for your post...
I have only been here how long? LOL!
Florida

 

[Robert E Holt]

Where in Florida? I am on business travel to Melbourne this week.

 

[A Random User]

Where in Florida? I am on business travel to Melbourne this week.

Tampa

 

[Robert E Holt]

Not too close.

 

[A Random User]

This is why I am proposing the idea of questioning conventional wisdom... it is my observations that "Wet" wood is less likely to break than "Dry". That in fact, usually "Wet" wood is more likely to tear along the grains, and not across.

That the separation of cambium layers from the heartwood does not occur from the bend, but instead from a fail in the bend and the energy of the bend being transfered throughout the different layers... causing a back n forth motion.

I am not just throwing this out to disagree with conventional wisdom... I think it is an all actuality a legitimate proposal based on first hand accounts of what I see happening. I think it is a subject worth considerable debate... it could change alot of how we understand and work in bonsai. Every time on does a bend, even a slight one, i think if they better understood the properties at work, they would be better armed with information of how to do the bend and less likely to have loss in doing so.Would love to here any opposing views as well. Perhaps there is something I don't understand, or are missing? Just trying to learn, understand, and question what I am doing.

Cruising at an altitude of 20,ooo feet.

 

[JohnnyFive]

This thread has been extremely thought provoking. Thanks for sharing!

 

[JoeR]

I think major branch bending needs to be talked about considerably more often. It is a subject I know nearly nothing about after being in this forum for close to a year? Maybe half a year?