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Thread: stop warping?

  1. #1

    stop warping?

    I'm new to woodworking. I acclimitised my wood to my workshop environment for a week, then planed and sanded my wood. At this point it was flat. A few weeks later it is slightly warped. It went from being perfectly flat on a table to not being flat.

    Is there something I can finish planed & sanded wood with that would stop it warping? I'm assuming I need to moisture lock the board essentially to stop the warping.

    I'm keen for the wood to look and feel as natural as possible !

  2. #2
    When wood is left laying flat on a surface, only one side gets air. If the wood is not in equilibrium with the environment, one side will gain or lose a little moisture, but the other side cannot. This causes wood movement, in your case, warp. Never leave a board laying flat on a table, floor, etc. with just one side exposed to the air. It needs to be stored where it can get air on both sides, or where neither side can get air, as in flat stacking boards. Just be sure to cover the top boards in the stack with scrap or nurse boards to keep them covered. Finishing the board without it being stable with the environment will only lead to more problems.

  3. #3
    Apologies I hadn't meant to give the impression that I had stored it lying flat, It wasn't.

  4. #4
    Join Date
    Feb 2008
    E TN, near Knoxville
    Wood naturally gains and looses moisture as the humidity changes in the environment.
    Wood that is not quite dry may warp badly as it dries.
    Wood that was air dried outside can warp as it dries in a less humid environment.
    Wood that was kiln dried can warp as it gains moisture in a more humid environment.
    Boards that are milled in a unconditioned shop then moved into a conditioned space can lose moisture and warp.
    Larger boards will in general warp more.
    Some species of wood are more stable than others.
    Boards with straight grain warp in different ways than those where the grain curves or runs at an angle, either across the face or through the thickness.
    Boards that are quartersawn may warp less. (If not familiar with this, look at the rings on the end grain and check the internet)
    Finish may help but in general doesn't stop the moisture change.

    Some more information might help. Perhaps you could say what kind of wood, the size and thickness, and the orientation of the grain and rings. Also, state where you live and if the wood was kiln dried or air dried, the moisture content if known, and more your environment, for example, if it was moved out of the shop and into another environment. These might give people some reference points on which to base useful comments and suggest strategies.

    What do you plan to build?


  5. #5
    Join Date
    Sep 2013
    Carrollton, Georgia
    paul, considering that you acclimated your lumber in your shop for a week before surfacing, which should be long enough if working with dried lumber, it's likely not due to moisture absorption or evacuation, unless the wood was not dried to working condition to start with, which is my guess. Regarding stopping the warping : Nature is going to do what it's going to do. Once Nature's done with your wood, i.e. it's dry, then you can take care of the shape of it.

  6. #6
    Join Date
    Sep 2013
    Wayland, MA
    Perfect flatness all the time is pretty much impossible because wood moves with changes in humidity. Traditional joinery and design has a lot of elements that compensate for this, modern indoor heating has made the problem worse with the potential for extremely low relative humidity in the winter. I try to keep my shop environment similar to my house to avoid bad surprises on transition, and try to let lumber acclimate in my shop for at least 6-12 months prior to use. I doubt much acclimation happens in a week.

  7. #7
    Quote Originally Posted by paul simonson View Post
    I'm keen for the wood to look and feel as natural as possible !
    The only things I'm aware of that stop a free-standing piece of wood from wanting to warp go against your last wish.

    Stabilizing wood with resin. Not too different looking and feeling from a thick coat of poly. Very expensive resin and the length is limited by the vacuum chamber size.

    Baking already dried wood in an oven. Looks like a quality dark stain has been applied. Sort of like kiln drying but with more heat(475f for 2-3 hours). This smokes up the house, but depending on the species that can smell good(sugar maple!!!). You're limited by the size of your oven. I can get 24" narrow lengths in mine. Technically this doesn't stop warping or expansion and contraction, just lessens it.

    Clamping it in place. It's not even practical 99% of the time. If it's clamped to a flat object it doesn't lose it's desire to warp, it just maintains its ability to be straight. Might still be a pain to assemble.

    The practical thing is to leave stock as large as possible as long as possible. Once it's cut and surfaced, assemble that day. Wait any longer and odds only slightly better than vegas you'll wish you hadn't.

  8. #8
    Join Date
    Dec 2010
    A week might not be nearly long enough for wood to acclimate to your shop. It all depends upon what the MC of the wood was compared to the EMC of your shop when you started using it and whether if was uniform through out. Unless the MC was within a couple of % of the EMC content when you brought it into your shop I don't think a week would be anywhere near long enough.

    How much the RH changes in your shop is another factor, and a big one if it changes a lot from day to day.

    Two of the best things you can do is buy and use a moisture meter, and hang a hygrometer and a chart showing RH vs. the EMC of wood on the wall of your shop. If you don't own a copy of Hoadley's book "Understanding Wood" that would be a good purchase, too.


  9. #9
    I'm with the "one week isn't enough" club. In my experience I like a month or more if possible. I also think the way you stack it matters too. stickers with some weight on top has never failed me. I just transferred a bunch of wood from my Father in laws's garage which tends to be damp to my attached garage for use in early September. More time won't hurt especially in turn of season situations. My 2 pennies.


    P.S. as others have said, the way you stack it after jointing/planing makes all the difference. Danny in post #2 nailed it.
    Last edited by Ron Citerone; 07-13-2018 at 7:36 PM.

  10. #10
    My projects rarely have wood that is completely flat, even when I am using plywood. Fortunately it becomes flat when I fasten it into the project. I recently finished a floor standing, 15 inch deep by about 30 inch wide floor to ceiling cabinet for our bathroom. To copy the vanity (mandated design decision) it had to have nearly 2 inch square legs running the full height. I faked those with pieces of 2x12 glued to 3/4 plywood with a little planned down 3/4 softwood. None of the boards I used were completely flat. The plywood wasn't but it was close. The 3/4 board might have been, I didn't really check it close. It was a very old piece of interior paneling. The 2x12 was pretty flat but wasn't terribly dry so it likely is still moving slightly. But when all these pieces are glued and screwed together into the cabinet, it is straighter than the walls in the bathroom.

    Long way of saying that it normally does not matter when our boards are not straight. For doors, it's nice to have some good stock and terrible to have bad stock. But frame and panel construction means we do not need big wide pieces of good stock. The doors on the subject piece are inset. I made them as big as the opening and then trimmed them to fit and have decent reveals. That also let me remove a little wandering of the 3/4 board frame of the door.

    A good bit of doing woodworking is learning how to deal with the fact that the boards are not straight or flat and even if they are at one point they probably will not be with some humidity change.

    Paint, poly and varnish all seal things up pretty well, however. That means that they dramatically lower the rate of moisture changes in the wood. So they reduce wood movement. But what keeps the board flat is normally the fact that it is fastened to another board which doesn't want to go the same direction.

  11. #11
    Did you face the wood on a jointer before you planed it?

    To get wood flat, it's a good idea to face it on a jointer, then plane it. Putting wood into a planer will press the wood flat, and it will spring back after being planed. The spring back can happen slowly, over a week.

    Some wood is flat and stable enough, and too wide, to skip facing on a jointer. My planer is 4" wider than my jointer, so I sometimes have to flatten wood by having some of the wood hang off the operator side of the jointer. I use a fence mounted guard for this.

  12. #12
    The wood wasn't done acclimating yet.

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