Re: Reaction Wood??? Andi??

"In the northern hemisphere this is formed in the upper side of the

> limb in hardwoods and the lower side in soft woods. The reverse is > true for trees in the southern hemisphere." >

Ken - I saw this statement in the book, also, and don't know quite what to make of it.

Reaction wood is a descriptor for the larger spacing of growth rings on one side of the pith relative to the other on branches. There is a difference in how the wood reacts as it's drying, which explains the name.

I'll have to dig into the literature to see if there is a difference among plant families in how the branches put on secondary growth. If the above statement is anecdotal in nature, it may just be referring to differences among plants that typically occur in one hemisphere vs the other.

Andi

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Reply to
Andi Wolfe
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The difference is between hardwoods and soft woods. On conifers reaction wood grows below the pith, on hardwoods reaction wood grows above the pith. For more detailed description see "Fine Woodworking on Wood and How to Dry It" page 60.

Chuck

Reply to
Mary Ann Mapili

Chuck. what you say here is already understood from the original message. What is not clear is that the author says this whole "softwood-hardwood thing" is reversed in the southern hemisphere.

James Barley.

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Reply to
James Barley

I suggest reaction wood describes the different way the wood reacts to the stresses in the limb. For a branch that is at an angle from the trunk, the lower portion of the branch is in compression, the upper portion in tension. The fibers in the tree no doubt "react" differently to tension and compression, hence the pith is off center and the rings are "eccentric". In the trunk, the rings are typically concentric since both sides are in compression. This is the case unless prevailing winds or lean cause unequal stresses on opposite sides of the trunk, in which case the pith will likely be off center and the rings "eccentric". I can't imagine why northern or southern hemishere would have an effect, but since coriolis is opposite above and below the equator, I suppose it's possible.

-- Lowell Converse

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Reply to
Lowell Converse

For a tree that is leaning off of vertical - the "uphill" side of each growth ring is in tension, stretched as it tries to bring the tree vertical, or at least prevent it from falling over farther. The growth ring on the "downhill" side of the tree isn't be stretched at all - but rather it's being compressed. Each behaves differently when cut, as in sawing a cross section into two halves.

Here's an illustrated and annoted explanation that may help

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Reply to
charlieb

Charlie,

One thing that you may want to add to your wonderfully illustrated explanation: the branch cut parallel to the ground will yield bowls with more symmetric grain, which IMHO is much more desirable than a little bit bigger blank.

Regards,

Reply to
C & S

Steve:

It's not clear to me what you mean by "the branch cut parallel to the ground will yield bowls with more symmetric grain"

Look at Illustration A & B on the following page I earlier pointed to.

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In both cases, the log is cut into two "halves" - along the Pith Line, "A" leaving the same amount of tension and compression wood in each "half" while "B" leaves all of the tension wood in one "half" and all the compression wood in the other.

One interpretation of the "parallel" part of your statement would be as shown on this temporary page I just put up for purposes of discussion.

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Rather than cutting along the pith line, this method would cut THROUGH the pith line at an angle - determined by a line parallel to the ground when the branch section was on the tree.

Is that what you had in mind? If not, could you clarify a bit and I'll try and illustrate it.

charlie b

Reply to
charlieb

B-cut will yeild symmetric grain (blanks c and d). A- will have the center of the grain *not* running through the center of the bowl (blanks a and b).

regards,

Steve

Reply to
StephenM

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