humidity problems

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Forum topic by kosta posted 09-30-2010 09:03 PM 1493 views 0 times favorited 9 replies Add to Favorites Watch
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946 posts in 3560 days

09-30-2010 09:03 PM

Topic tags/keywords: pine clamp

Yo whats up everybody I glued up 4 panels last week and I flattened them on tuesday and they were pretty flat. It was about 60% humidity at the time. Yesterday it was about 100% humidity outside and I went to look at the panels and they were really really warped. Once the humidity goes back down will the panels go back to the way they were or are they permently warped. Any ideas on how to get the panels flat and how to keep them that way?

9 replies so far

View NathanAllen's profile


376 posts in 3349 days

#1 posted 09-30-2010 09:10 PM

How thick are the panels? Is the grain alternating? What is the direction of the warping?

View kosta's profile


946 posts in 3560 days

#2 posted 09-30-2010 09:29 PM

they are just under 3/4 in the grain is going in the same direction and the warping is on edges. The center is the high spot in the panel. they are 32 in long and 22 in wide

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946 posts in 3560 days

#3 posted 09-30-2010 10:20 PM

I took off a good amount of wood cause the panels werent flat after I glued them up. I used water to clean up the squeeze out from the glue up then I flattened the panel the next day. The wood has been sitting in my shop for about a month and I milled up the parts for the panels about 1 week before I started gluing the panels up.

View Chinitorama's profile


105 posts in 3504 days

#4 posted 09-30-2010 10:34 PM


I think CessnaPilot is right. Just rewatched your blog vid (Well done vids, by the way). It looks like more wood was taken off one face of each board during machining, unless you fed them through a planer after jointing. That and the wet rag for glue cleanup definitely would contribute to the panel warping.

The big swing in humidity in your shop might have triggered some spring back (?) after you flattened your panel. A slight mod to your clamping may help. I like to place clamps so that every second clamp is on an alternate face. I use parallel clamps like you do, but avoid squeezing my glue ups from one side only. The idea is to avoid imparting stresses into the panel as even parallel clamps can deflect a little. I could be alone on this way of thinking tho.

In the end it could just be that the pine was flat sawn and had a lot of reaction wood in it.


View CampD's profile (online now)


1734 posts in 3691 days

#5 posted 09-30-2010 10:58 PM

I’ve had this problem before. To straighten them out you have to sandwich them between 2 good and flat boards, thicker the better and leave them for some time. I now went to 4 sided clamps when I glue-up
wider panels and leave them for a couple days that way.

-- Doug...

View kosta's profile


946 posts in 3560 days

#6 posted 09-30-2010 11:42 PM

yeah I see what your saying. Now that it was brought up the rag that I used was really soaked with water.

I will try clamping the panels though

View kosta's profile


946 posts in 3560 days

#7 posted 10-01-2010 05:33 AM

I just went out to the shop after clamping the 4 panels for about 7 hours they definitely got flatter. I am going to leave them clamped up overnight so that they can fully flatten.

View TominTexas's profile


42 posts in 3041 days

#8 posted 10-01-2010 08:07 PM

Cupping/Warping of a panel is caused by one surface becoming drier than the other side. When the one surface gives up more moisture than the opposite side, the dry side pulls the moist surface/side creating the cup effect. Panels that have been machined, planed and generally have new surfaces exposed allowing internal moisture in the boards to be exposed. After flattening a new panel, it’s a good idea to store them by stickering as you would store lumber. By allowing moisture to escape from all surfaces, cupping will be minimized. Most panel warping that I’ve experienced has occurred when I forgot and left a new panel laying flat on a bench or table – just overnight is enough to cause the warp.


-- East Side of Big D

View andyboy's profile


565 posts in 3478 days

#9 posted 10-06-2010 10:14 AM

Hey mate. When my wood is totally dry it can still warp. I always store my panels strip stacked on my bench. If they are being left for the weekend I might even cover them. Tom has so hit it on the nail. Good on ya Tom. Let that air circulate evenly.

-- Andy Halewoodworker. You can't finish if you don't finish. So finish it, because finish is everything.

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