Need help: How to stabilize wood after machining.
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    Default Need help: How to stabilize wood after machining.

    Hi all,
    I've machined a lot of metal, but just started doing some wood. I made and aluminum trey with a wood sleeve that slides around the metal to contain the contents. All came out great. I live in a humid environment (Austin Texas). The box worked beautifully until we had a dry front blow through the dropped the humidity for a week. My wood sleeve shrunk so much, I couldn't get the sleeve off the box. As soon as the humidity returned, the sleeve worked fine again. Sure I could machine more material away for more clearance, but the degree of shrinkage/expansion is so great, I'm afraid the fit would get very sloppy in those humid condition.

    Are there any methods to "stabilize" the wood post machining ?. The wood I've used is mesquite and Granadillo. When I purchased the wood, the vendor stated the wood was already "cured" etc. Would soaking in hot oil or anything seal the cellulose and prevent growth/shrinkage ?.

    Thanks in advance
    Matt

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    West System epoxy or design for the wood to do its thing. Wood can be very stable running with the grain but 90 degrees to the wood and there is a lot of movement. I have a supply of 50 year+ wood that is stabilized over time that I use for model building, I get it from discarded and damaged furniture.

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    Mesquite and Granadillo are expensive.

    For unfinished wood:
    If you have a good fit now then I would use a brick of wax and rub the sliding surface of the wood. Coat the end grain too. You might even like the finish after you buff it out. The stuff I have is labeled Parowax which can be used for making candles. If you have a white candle then try it.

    For finished wood:
    Bare wood gets a few wipes of thinned shellac.

    The perfect thing would be to make your wood piece to final dimension at the center of your humidity range. That is too perfect.

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    I have had good luck with water-based polyurethane. It is available at Home Depot and Lowes. The oil-based poly works too, but is smelly and takes a while to dry. Regards, Clark

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    when I was building doors, I used a product call Nelsonite on the door after it was done. Solved a lot of problems.It was a commercial product. I don't know if you can still buy it. Bob

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    Part of designing with wood is choosing the type of wood and grain direction to accommodate changes. It's the same reason people use floating panels and don't glue up all four sides of some projects. Get the design as good as you can, then apply the additional measures.

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    Probably the ultimate, although it may be more expensive than you want is Epo-Tek 301.

    This is a very low viscosity transparent epoxy with high UV resistance. It has been used by museums for artifact preservation.

    To use, you would machine the wood under dry conditions and then impregnate it. Any time wood is machined during high humidity shrinkage is an issue. You mill it while it is dry and then seal it to prevent or reduce moisture absorption. This is also true when using oil or wax.

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    We use danish oil and keep wood wet until it stops absorbing.

    Most brush and wipe but we found continuing to brush on over say 30 minutes or so the wood soaks it in deeper resulting in a deeper tone and better finish.

    We wet sand with 600 paper after it dries first coat and use same oil as the wet part so any raised fibers are removed with the paper.

    The finish is wicked into any open pores.

    You could do same with either a thin epoxy or other oil finish.

    The oil may cause dimension change so not sure how it would work in your case.

    But we'll soaked should limit movement.



    Sent from my SAMSUNG-SGH-I337Z using Tapatalk

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    The suggestions above are good ways to retard the loss or gain of moisture, but eventually it will equilibrate.

    The only way to keep wood from moving across the grain with humidity changes is to impregnate or encapsulate it with resin that cures without solvent loss. Encapsulated wood, think bar tops with coins, etc, is not my favorite look, and impregnation is difficult. First a vacuum is drawn, and then the resin is injected under pressure and cured. Not an easy process without serious equipment, and then mesquite and granadillo are extremely dense and might be impossible to impregnate.

    That being said, mesquite has very low shrinkage values - Radial: 1.6%, Tangential: 3.2%, which mean that it should be much more stabile than most other woods, plus the density should slow down the movement of moisture.

    You're going to have accept some movement or design so the critical dimensions are along the grain

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    Very helpfull posts. ..

    Thanks everyone !!

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    Not all woods can be stabilized but some species can, and will keep very close tolerances for many years. I still have my slide ruler from university days. It was made by Hemmi Bamboo Slide Rule Company Ltd. Made out of bamboo it kept perfect tolerances and still sliding smooth like butter 50 years later. An even older slide ruler made out of boxwood is almost as good (and a plastic one got stuck years ago)
    Hemmi used laminated wood and I think it was pressure treated, possibly with diluted casein. At the time Hemmi started making slide rulers in 1912 casein was the only waterproof glue for wood. Casein is moisture resistant and has superior aging characteristics. I was very successfully using casein for laminating wood, though did not try pressure treating.

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    Agree with Richard.

    It's been a dozen years or longer, I experimented with putting the handles ("totes") for my infill woodworking planes in a peanut butter jar, pulling down a vacuum and letting them set for a while, then introducing WEST epoxy, shaking the parts around to get them coated while re-establishing the vacuum until the epoxy foamed, and then letting off while continuing to agitate the parts for a 1/2 hr or so. Then I removed them and wiped them down and let them set up.

    Sadly, in cocobola and African Blackwood, it never actually penetrated to amount to any useful improvement.

    My working solution evolved to soaking the wooden parts in Penofin marine oil, wipe down, let set, sand, do some occasional spit coats, and after a week or 2, wax them with Tre-wax. (I prefer the smell of Tre-wax, and think it is also a better product than the stinkier versions like Johnsons, but really, it is just personal predjudice.) I would probably experiment with cooking them in beeswax if I took it up again, but not saying there is necessarily an advantage beyond the marketing possibilities.

    PS, the above treatment makes some very nice handling handles with a soft easy maintenance patina. As has been said, however, it does not eliminate gradual change with longer term (more than a few days) humidity changes.

    smt

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    If you want the best stabilization I would send it to K&G knife supply and have them do. They have very good resins and it sits under vacuum for many days. A lot of woods be 50-100% heaveier afer being stabilidzed by them. K & G Finishing Supplies - Stabilizing - Home

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    Quote Originally Posted by Conrad Hoffman View Post
    Part of designing with wood is choosing the type of wood and grain direction to accommodate changes. It's the same reason people use floating panels and don't glue up all four sides of some projects. Get the design as good as you can, then apply the additional measures.
    This is by far the best answer. - which way is your grain running?

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    Quote Originally Posted by Wsurfer View Post
    Hi all,
    I've machined a lot of metal, but just started doing some wood. I made and aluminum trey with a wood sleeve that slides around the metal to contain the contents. All came out great. I live in a humid environment (Austin Texas). The box worked beautifully until we had a dry front blow through the dropped the humidity for a week. My wood sleeve shrunk so much, I couldn't get the sleeve off the box. As soon as the humidity returned, the sleeve worked fine again. Sure I could machine more material away for more clearance, but the degree of shrinkage/expansion is so great, I'm afraid the fit would get very sloppy in those humid condition.

    Are there any methods to "stabilize" the wood post machining ?. The wood I've used is mesquite and Granadillo. When I purchased the wood, the vendor stated the wood was already "cured" etc. Would soaking in hot oil or anything seal the cellulose and prevent growth/shrinkage ?.

    Thanks in advance
    Matt
    Guitar makers use "torrified" wood. It's MUCH more stable than "cured" wood. To torrify you heat it in the oven ramping very slowly up to around 160C and hold it there for some hours. Torrifying makes the wood slightly spongy and it can become difficult to glue this kind of wood with bone glue - it doesn't wet well. In general, stabilizing after machining is not as good as before.

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    Here is an interesting thread from a boat building website. I came across it awhile back when researching info concerning the use of borates as a wood preservative/ insecticide and the means of using a carrier to introduce it into the wood fibers. The thread compares and discusses the use of PEG, PG, and EG as wood stabilizers.

    http://forum.woodenboat.com/showthre...ted-wood-safey

    MILO

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    I use several flavors of Briwax. On the can it says "By Appointment to Her Majesty The Queen". If that means the stuff is used is Buckingham Palace ...

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    Use plywood. If you get a good grade of plywood like baltic birch, it will have very little shrinkage in any direction. You can add a thin veneer on each side of mesquite, and add mesquite T-molding on the edges.

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    I've done a little work vacuum stabilizing mesquite for some knife handles and jewellery both with heat activation and a setting agent. I had better results with the stabilizing fluid that uses a setting agent by out-gassing it before adding the catalyst. Also a couple hours in a 160 degree oven before stabilization helps get the moisture out. Then a CA finish and I havn't had any problems with anything absorbing moisture. Several of my pieces live in Galveston who has humidity Austin can only imagine.


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