LumberJocks

confused about wood movement with pallet glue up for table top

  • Advertise with us

« back to Wood & Lumber forum

Forum topic by Spikes posted 11-28-2018 04:14 AM 911 views 0 times favorited 14 replies Add to Favorites Watch
View Spikes's profile

Spikes

125 posts in 496 days


11-28-2018 04:14 AM

Hi,

I rescued some pallet wood, joint the sides and glued it up. It came out nice and flat. I left it there for a few days as I got busy with other stuff (it rained in the meantime) and when I went to pick it up it looked like this:

first off, is this considered wood movement? any time I read about the topic it seems to talk about dimensions changing, vs cupping etc, just trying to make sure I use the right terminology.

Second, I don’t know what sort of wood this was, it seems pretty dense/old, it was in a pile of thrown away pallets that had been in the rain for long, but anyways, I didn’t quite see grain circles so I just oriented it as it looked better. The fact that it cupped like that was quite surprising, was there anyway that I could have avoided it?

Third and maybe most important/confusing… after a day laying flat on that table the cupping was completely gone! how come? I didn’t even put any weight on it. And to top it off, a few days later it was cupped again and then, boom, cup gone again a day later. I’m completely at a loss of what’s going on here, any idea?

Last but not least, given how much this thing is moving, even if I use buttons with rabbets to allow for “wood movement”, how is that going to be of any use against cupping? should I just throw this away or is there a way I can mount it to a base safely?

thanks,

Spike

-- Don't worry about making progress, worry about practicing. If you practice you will make progress even if you don't want to.


14 replies so far

View Rich's profile

Rich

4693 posts in 1040 days


#1 posted 11-28-2018 05:23 AM

Don’t toss it. A smooth arch like that is easy to pull flat. I can’t tell from the photo how thick it is, but if that’s a 3/4” or thicker board it’ll make a nice table top. Use Z-clips or some means to pull it down to the base.

-- My grandfather always said that when one door closes, another one opens. He was a wonderful man, but a lousy cabinet maker

View HokieKen's profile (online now)

HokieKen

10288 posts in 1589 days


#2 posted 11-28-2018 12:13 PM

If you look at the endgrain of a log or a board, the growth rings are circular. Think of wood movement as each of those circles expanding and contracting. Depending on how the lumber is milled, that can manifest as a change in the width of the board or cupping. In actuality, it’s a combination of both. The reason quartersawn lumber is desirable for dimensional stability, is because the rings become approximately straight. No curve = no cupping.

All that being said, I think Rich is right on. That’s a smooth curve and a relatively thin panel. From your description, all your seeing is normal wood movement due to humidity swings. I think if you pull it flat, it will stay that way.

-- Kenny, SW VA, Go Hokies!!!

View jutsFL's profile

jutsFL

180 posts in 292 days


#3 posted 11-28-2018 02:10 PM

So my thoughts are the same as above. Its fine as is, it will pull flat very well from the looks if it.

As for why it happened and continues to evolve – I’m guessing youre laying it flat on something as pictured… The top will then dry quicker as it has the air flow, and the bottom is sealed off by what youve layed it on- creating a side that has more moisture than the top. As the top dries it pulls the cup, you flip it over, and the same process starts moving it the other way.

Leave it on edge, so air hits both sides evenly… Preferably with some air movement – fan etc… And the problem will minimize, but it wont go away completely. Wood does what it wants to, no matter how careful you are.

-- I've quickly learned that being a woodworker isn't about making flawless work, rather it's fixing all the mistakes you made so that it appears flawless to others! Jay - FL

View HokieKen's profile (online now)

HokieKen

10288 posts in 1589 days


#4 posted 11-28-2018 02:20 PM

One other thought. You said this was pallet wood. Some pallets are treated with chemicals for certain industries. Depending on what it was treated with, the treatment may have had some effect on the characteristics of the wood. For instance, if it was sealed with something while the wood was still green, you may be getting exaggerated movement because the wood still hasn’t dried out.

-- Kenny, SW VA, Go Hokies!!!

View jutsFL's profile

jutsFL

180 posts in 292 days


#5 posted 11-28-2018 03:39 PM



One other thought. You said this was pallet wood. Some pallets are treated with chemicals for certain industries. Depending on what it was treated with, the treatment may have had some effect on the characteristics of the wood. For instance, if it was sealed with something while the wood was still green, you may be getting exaggerated movement because the wood still hasn t dried out.

- HokieKen

Nice point. Hadnt thought of that.

-- I've quickly learned that being a woodworker isn't about making flawless work, rather it's fixing all the mistakes you made so that it appears flawless to others! Jay - FL

View Spikes's profile

Spikes

125 posts in 496 days


#6 posted 11-28-2018 03:51 PM

super quality feedback as usual. Good to know that this is still “wood movement”, I wasn’t clear if expansion/shrinking was only what qualified as such. Also interesting point about the chemicals on pallet wood, I had heard about it but didn’t factor it in for wood movement.

One follow up comments to what @justFL said re laying it flat… it was actually lying on a side when it first cupped and I put it flat on the table hoping that it would help to flatten it down. However I then left it on the table and it cupped again. So it doesn’t seem to matter how I store it, it’ll continue cupping either way, but from all the feedback it sounds like that’s ok and it will still work once I zclip it to the frame.

thanks again

-- Don't worry about making progress, worry about practicing. If you practice you will make progress even if you don't want to.

View Rich's profile

Rich

4693 posts in 1040 days


#7 posted 11-28-2018 04:08 PM


zclip it to the frame.

thanks again

- Spikes

One tip for the clips. Cut the slots for the clip maybe 1/32” to 1/16” further than the height of the clip. That way they’ll be sure to be pulling tight.

-- My grandfather always said that when one door closes, another one opens. He was a wonderful man, but a lousy cabinet maker

View GrantA's profile

GrantA

1682 posts in 1858 days


#8 posted 11-28-2018 04:11 PM

sorry not sorry :-) I couldn’t resist! if it was flat to start then yeah what has been said, worst case though just rip it and start over

View Lazyman's profile

Lazyman

3686 posts in 1838 days


#9 posted 11-28-2018 04:33 PM

Do you have a moisture meter? Might be a good idea to check where the moisture level is before you use it in a project. You want it well below 20% and probably closer to 8-12% before you use it. The dryer the climate, the dryer it needs to be.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Phil32's profile

Phil32

598 posts in 354 days


#10 posted 11-28-2018 05:20 PM

The comment on chemicals sprayed on the pallet raises some questions about using this for a table top. You may not plan to serve food directly on the wood, but who knows the risk of wiping the table with a cloth. If the pallet was sprayed with chemicals, it was not done to make the pallet food safe!

-- Phil Allin - There are mountain climbers and people who talk about climbing mountains. The climbers have "selfies" at the summit!

View Rich's profile

Rich

4693 posts in 1040 days


#11 posted 11-28-2018 05:58 PM


The comment on chemicals sprayed on the pallet raises some questions about using this for a table top. You may not plan to serve food directly on the wood, but who knows the risk of wiping the table with a cloth. If the pallet was sprayed with chemicals, it was not done to make the pallet food safe!

- Phil32

The real risk occurs during milling when the dust gets in the air. Once it has a film finish on it, I wouldn’t hesitate to eat off of it.

-- My grandfather always said that when one door closes, another one opens. He was a wonderful man, but a lousy cabinet maker

View Woodknack's profile

Woodknack

12870 posts in 2831 days


#12 posted 11-28-2018 06:05 PM

Wood movement is hydraulic, it moves as water moves in and out of the wood. That movement can show up as cracks, bowing, twisting, or cupping; and sometimes it moves back.

-- Rick M, http://thewoodknack.blogspot.com/

View HokieKen's profile (online now)

HokieKen

10288 posts in 1589 days


#13 posted 11-28-2018 06:13 PM



The comment on chemicals sprayed on the pallet raises some questions about using this for a table top. You may not plan to serve food directly on the wood, but who knows the risk of wiping the table with a cloth. If the pallet was sprayed with chemicals,it was not done to make the pallet food safe!

- Phil32

Actually sometimes it is. For pallets used in the food industry for instance. But, Phil’s thought is valid. I know some pallets are treated with creosote. I wouldn’t eat off creosote.

-- Kenny, SW VA, Go Hokies!!!

View fuigb's profile

fuigb

559 posts in 3408 days


#14 posted 11-29-2018 03:25 AM

Dry that stuff! The tenor of the remarks above re: moisture content and movement are in line with my experience. Since I found a steady source for decent hardwood pallets (and made a kiln with scavenged material) I’ve hardly gone back to my local mill and my stock is great. The trick is to keep the pipeline full: while one batch is drying another wet pile is growing, and all the while I’m working with whatever has already been dried and and dimensioned. Plenty here about kilns and air-drying, so start with some research there and then see where things go.

-- - Crud. Go tell your mother that I need a Band-aid.

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com