Taking the cup out with an Iron

I’m making a fancy box that will be filled with chocolates. I’m using European beech that I’ve had for quite a while. After re-sawing it, the darn thing cupped. Sometimes it happens and sometimes it doesn’t, it’s all part of the journey and you just deal with it. Unfortunately, the cup was really prominent and I cannot afford to plane out as it’s the lid and I want it to remain as close as I can to 3/4″ thick.

So what can I do? I can cry, I can throw the timber across the room or I can iron it out, and I chose option three. I wet the timber through a wet paper towel and lay it across the wood.

Next, I lay the hot iron across the paper towel which made it cup in the opposite direction.

Plenty of steam came out, which is why the picture is so foggy. I did this as many times as necessary to get the cup out. In my case, it was three times.

That’s close enough. As you can see, most of the cup is gone. Instead of planing it now, I stickered them to allow nature to take its course and let the timber move and acclimate for a couple of days. Sometimes you may have to wait a couple of weeks for the wood to properly acclimate and stop moving around on you. This is not a permanent solution but only a quick fix if you needed to attach it to something. Unfortunately, it cupped again and again and again even after I had placed heavy loads on it to stop it from. I was hoping it would acclimate to the shops environment and stay flat, but it didn’t. It just cupped to the same level it did the first time round as if it had memory. There wasn’t anything I could do change the situation. Wood moves and unfortunate for me it moved because it wasn’t kiln dried properly in the first place. This is an on going issue I am having with my timber yard that for one reason or another it never get addressed.

4 thoughts on “Taking the cup out with an Iron

  1. One of my very early woodworking projects (back in the power tool days) was a bedside table of maple with cherry drawer front from a magazine article plan. The maple top was a glue-up that cupped pretty badly. I was going out of town for a weekend and I laid a very wet towel over the concave side with some plastic wrap over that to reduce evaporation. When I got home, the panel was much better. And remarkably, it stayed reasonably flat. I’m sure being attached to the table has helped keep it flat over the years.

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    1. I haven’t tried using plastic wrap, sounds like a good idea. I have beech that’s been in a plastic wrap since when I first bought it over ten years ago. It was going to be for a project that never happened. When I unwrapped it a few months ago and resawed it, water came out one end. So, definitely plastic wrap hold the moisture.

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  2. Hi Salko,

    The warp that occurred after resawing was probably due to case hardening. This is present in most boards and, to an extent, is normal. Both of the resawn pieces cup toward the sawn side. This usually happens right away after resawing but sometimes is delayed. Because you had the original board for a long time, it is unlikely to have had a moisture content gradient through its thickness, so this would not explain the warping after resawing. Here’s some more info on this:
    http://www.rpwoodwork.com/blog/2008/11/07/more-on-resawing/
    http://www.rpwoodwork.com/blog/2009/01/09/resaw-rethink/

    Anyway, you might try wetting the concave side (regardless of the ring orientation) of the resawn board while several clamps restrain the board across its width. This will cause compression set of the wood cells on the side that was wetted. When the board dries it should be closer to flat, with a little luck. Bob Flexner explains this method:
    https://www.popularwoodworking.com/editors-blog/a-method-for-correcting-warps/

    Ugh, wood is tough to deal with sometimes. Thanks for writing.

    Rob

    Liked by 1 person

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