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Not much meat to this question. What is wood stabilization and why would I want to do it? It think it has to do with turning but are there other reasons that I would want to do it.

This question is based on a comment from this answer:

It's worth noting that you can stabilize punky spalted wood - grfrazee

  • Context? This could mean one of several things... – keshlam Aug 1 '15 at 20:53
  • @keshlam ... Best context I could muster – Matt Aug 1 '15 at 20:54
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Wood stabilization typically refers to reinforcing wood against inherent defects or weaknesses.

In turning, stabilization may mean anything from filling cracks with epoxy, to impregnating the wood with resin.

More generally, you can stabilize a crack with a butterfly inlay or you can again use epoxy or some other filler.

In the case of turning, the purpose of stabilizing the wood is to strengthen it against cracking and shattering while working on the piece. In other cases, you may want to showcase a crack (or other "defect") as part of your piece's character, but you want to prevent the crack from spreading further, possibly to the point of causing the piece to break or fail. For example, butterfly/bowtie inlays are commonly used to stabilize cracks in large wooden tabletops.

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When talking about stability, it is necessary to distinguish between structural stability and dimensional stability. The means for reinforcing spalted wood (plastic resins, butterfly inserts, etc) fall within the realm of establishing structural stability.

During the 1970's a chemical means of maintaining dimensional stability using a warm solution of polyethylene glycol (PEG) became popular. Brought to the world's attention by the US Forest Products Laboratory in 1959, the process is basically to soak the wood in water for a couple of days then submerge it in a heated solution of PEG and water for a few or several days. This causes naturally occurring moisture to be displaced by the PEG and to no longer be subject to the vagaries of dimensional changes brought on by changes in humidity without seriously affecting workability and structure. It is most appropriately used for turnings, carvings and other projects that employ thicker wood that might balk at conventional drying processes.

PEG is not a panacea and PEG treated wood has its problems, specifically, gluing, finishing, and corrosiveness. Its waxy finish resists some glues, but there are viable work-arounds. Polyurethane and Danish oils work well as finishes, but traditional varnish and lacquers should be avoided. PEG is corrosive to most metals except stainless steel, so fasteners and attachments should be carefully considered.

PEG is not good for all hardwoods (hard maple, cherry), but is especially friendly to walnut.

There are several suppliers of PEG (A search for "PEG wood" will set you on the right track). This search will also lead you to specific instructions for time, temperature, concentrations which vary depending on the source. A comprehensive, but dated, discussion of how and when to use PEG is found in this article from Oregon State University.

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When woodworkers talk about "stability" they are referring to the tendency of the wood to change shape. "Stablizing" wood means doing something to it that would prevent it from changing shape.

Normally the biggest cause of instability is a loss (or gain) of moisture, causing part of the wood to shrink (or expand). This can lead to warping or twisting.

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Aside from stabilizing wood through chemical means- petrifier, glues, epoxy, etc. or mechanical means- butterflies, other wood or metal fasteners...

When I ponder wood stabilization my mind goes to, and stays at, moisture content (mc).

Stable wood, to me, means ensuring there is as little difference as possible in the percentage of moisture between the surface, core, and everywhere in between. The overall amount of water isn't as important as the consistency of the water throughout. All seasonal movement is directly related to the amount of moisture in a board AND the varying degrees of difference within.

When the surface mc and the core mc differs by more than just a little, this is called "case hardening"

If you have ever ripped a board and had it pinch the blade (scary,right?) or have the two pieces coming out like bananas in opposing curves (sometimes twisting so badly the piece becomes firewood)- you have experienced case hardening. Splitting the board relieves some of the unequal tensions between the cells of the unevenly dry board (the drier cells are tighter and pulling together and the wetter ones larger and pushing). Then a new type of tension is created within each of the new boards.

Drying kilns combat case hardening by injecting steam into the kiln at the end of the drying process to equalize the surface mc and the core mc as much as possible. Impossible as it is to make 100% even mc across any board, this gets it close to the consistency of a multi-year air dry.

This is why, even when using equalized wood, you must mill your parts oversize- then work them back to square and true to their final size.

I have heard that some people will take a board they are about to mill down to final size and drop/throw on the floor in an effort to "pre-relieve" the board of some internal tensions... maybe works?

As a cabinet maker I am less concerned with whether my material has a total mc of 8% or 13%, than how much the content varies within each rough board prior to milling into smaller final sizes. Also, how much the mc varies board to board within the unit of boards.

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