Wood bowing

[Whisper]

I just got some nice woods from Heritage and I noticed that a few of the pieces are starting to bow. They are not really thick and they were flat when they arrived. There's been a lot of humidity and rain here and I guess that is what is affecting some of the boards. I've put them under other wood and heavy items to try to flatten them out, but I don't know if that will work or not. They're inside the house, not outside or in a shed or anything like that.

Any ideas? I'm saving this wood until I'm sure I won't butcher it.

Edited January 17, 2020 by Whisper

[LarryEA]

There was a discussion a few years back about bowing wood. You might want to look for it.

Anyway, in part of the discussion was how to use a heat gun to remove the 'bow'.

The heat gun method does work by gently heating the center of the wood.  

I suppose this removes moisture causing the wood to 'straighten'.

Flattening boards with Heat? - by Mauricio @ LumberJocks ...  I have not read this but maybe it will 

provide some info...if not ...do a search

 

[Whisper]

11 minutes ago, LarryEA said:

There was a discussion a few years back about bowing wood. You might want to look for it.

Anyway, in part of the discussion was how to use a heat gun to remove the 'bow'.

The heat gun method does work by gently heating the center of the wood.  

I suppose this removes moisture causing the wood to 'straighten'.

Flattening boards with Heat? - by Mauricio @ LumberJocks ...  I have not read this but maybe it will 

provide some info...if not ...do a search

 

Wow, that's a BIG board that guy is trying to straighten out. Mine are just small, so maybe this will work on mine, too. It's green poplar that is doing the bowing. And I received a big piece of purple heart that was already bowed when it arrived. That kinda made me sad, I really wanted that one to be a good piece.

[OCtoolguy]

I had a piece of 1/4" red oak that warped on me so I sprayed the cupped side with water. I got it pretty damp. Then I clamped it cup side down to my work bench. I left it that way for a few days. When I finally unclamped it, it was flat once again. It was 6" wide and 48" long. It worked great. I don't have room to sticker my wood so I was happy to find this worked. Give it a try.

[LarryEA]

I do not know much about this.  Will the wood re-bow after you de-bow? 

 Moisture and lack of....basically,    When humidity increases, the wood absorbs moisture from the air causing the woodto expand. When the humidity decreases, the wood releases water into the air and thewood shrinks.

I cut a beautiful plaque for my brother-in-law. He hung it up in a very dry room. The piece warped and blew apart. 

This is why plywood is great for scrolling, each layer is opposite. 

Experiment...

[new2woodwrk]

3 hours ago, LarryEA said:

I do not know much about this.  Will the wood re-bow after you de-bow? 

 Moisture and lack of....basically,    When humidity increases, the wood absorbs moisture from the air causing the woodto expand. When the humidity decreases, the wood releases water into the air and thewood shrinks.

I cut a beautiful plaque for my brother-in-law. He hung it up in a very dry room. The piece warped and blew apart. 

This is why plywood is great for scrolling, each layer is opposite. 

Experiment...

Yes, sometimes - it depends on the water content of the wood, your local weather etc

I have tried several times to remove the bow from large pieces of plywood - it has always come back no matter how long I let it acclimate or sit. I have always had to cut out the bow and use the sides.

This is the reason I try not to order too much wood anymore, as I've had to do this on several large 1/4" and 1/2" boards - really pisses me off because plywood is very expensive here. At least to my wallet

my suggestion is to see if  you can use parts of the board where the bow is not - usually on the sides you can cut away the bow if you can't get the bow out.

Just my 2 cents worth

[JustLarry]

7 hours ago, Whisper said:

  And I received a big piece of purple heart that was already bowed when it arrived. That kinda made me sad, I really wanted that one to be a good piece.

Have you contacted Heritage on this?  Their order blank shows a pretty good guarantee on their wood.  Shows they will replace or refund is not satisfied.

Larry

[Whisper]

26 minutes ago, JustLarry said:

Have you contacted Heritage on this?  Their order blank shows a pretty good guarantee on their wood.  Shows they will replace or refund is not satisfied.

Larry

 

It's not worth the hassle to me. I can just cut the flat parts off and use it that way. Plus I got a good deal on the wood and don't want to cost Heritage shipping costs since it's not that big of a deal.

[kmmcrafts]

I go and hand pick my lumber to help avoid this issue.. If you look at the grain lines and they are far apart.. better chance for cupping like this... If the lines are very tight ( close together) less cupping.. and... I've never had a quarter sawn board cup like this ever... The thinner boards are more prone to cupping because there is less mass to it to dry out.. or absorb moisture... but all of them will do it.. To help..prevent it.. clamping them to other flat boards with some clamps can help keep them flat if you can't sticker them..  

[Bill WIlson]

Warping and cupping can be caused by several factors.  It can be anything from how the tree grew, to how it was sawn, dried and stored, to environmental changes prior to use.  

At your point, about the only thing you have any control over is the environment the wood is in.  Sometimes wood cups because of unequal release of moisture between the top & bottom surfaces.  This can sometimes be corrected by applying heat, moisture etc to try and equalize the moisture again.  This doesn't always work, but it's your best bet.  Sometimes wood is just bowed or warped and even if you are able to straighten or flatten it temporarily, it may not stay that way.

I once cut a small plaque out of a nice flat piece of 1/2" red oak.  I dyed it with a water based dye and let it set on the bench to dry.  I checked on it a couple days later and it looked like a potato chip.  I had never seen a piece of wood curl up like that.  I flipped it over and let it set an other couple days and it flattened back out perfectly.  I was lucky.  I caused my own cupping problem by not letting the piece release the moisture from the dye equally, from both sides.  Once it had a chance to dry equally, it returned to it's "natural" state.  Sometimes that natural state is warped/cupped and there is little to be done about it, short of milling it flat, which only works if the piece is thick enough to begin with.

 

[Lucky2]

Any wood I purchase off of the internet even from wood dealers, unless to large I store in clear plastic garbage bags. This works great for me, especially, with all of the thin veneer I purchase. It used to bow so much it looked like a rippled potato chip, but not since I started storing it in plastic bags.

 

Len

[OCtoolguy]

13 hours ago, LarryEA said:

I do not know much about this.  Will the wood re-bow after you de-bow? 

 Moisture and lack of....basically,    When humidity increases, the wood absorbs moisture from the air causing the woodto expand. When the humidity decreases, the wood releases water into the air and thewood shrinks.

I cut a beautiful plaque for my brother-in-law. He hung it up in a very dry room. The piece warped and blew apart. 

This is why plywood is great for scrolling, each layer is opposite. 

Experiment...

So far, the board that I "de-bowed" has stood along a wall with my other woods and has remained flat. I live in So Cal, 1 mile from the ocean. We have moderate humidity and also the dry Santa Ana winds. It has been a rainy year also. When I first bought the wood, it came shrink-wrapped along with some other boards. The oak was the only one that warped after taking the wrap off.

 

[Scrappile]

I had a piece of maple I purchased off the internet that cupped on me.  I got it flattened by moistening the cupped side and weighting it until it dried.  I used it to cut a picture of "The Last Super".  It cupped again as I was scrolling.... It is still leaning against the wall waiting for me to decide what to do about it.  Maybe, gets cold enough I will put it in the stove.  There  is a part of this that is vendor dependent.  I buy from one vendor that most often the boards cup.  Not sure why but they do.  I still will buy from them because they have some species that I can not get elsewhere in the same thin pieces.  I will say, I have started buying from Cherokee woods and so far not one board I have received from them has cupped.  They are west coast, I am west cost.  The other place is east coast.  Maybe it is the difference in climate...?

[OCtoolguy]

3 hours ago, Scrappile said:

I had a piece of maple I purchased off the internet that cupped on me.  I got it flattened by moistening the cupped side and weighting it until it dried.  I used it to cut a picture of "The Last Super".  It cupped again as I was scrolling.... It is still leaning against the wall waiting for me to decide what to do about it.  Maybe, gets cold enough I will put it in the stove.  There  is a part of this that is vendor dependent.  I buy from one vendor that most often the boards cup.  Not sure why but they do.  I still will buy from them because they have some species that I can not get elsewhere in the same thin pieces.  I will say, I have started buying from Cherokee woods and so far not one board I have received from them has cupped.  They are west coast, I am west cost.  The other place is east coast.  Maybe it is the difference in climate...?

That and the 3 hour time difference Paul. You just never know.

 

[Lucky2]

Another thing that helps prevent cupping of the boards you buy, is to store them with weight stacked on top of it. And sometimes, I even store some pieces that I'm working on with weight on top of it. Especially, if I won't be getting back to the project for a while, I find oak to be the worst for cupping.

 

Len

[JTTHECLOCKMAN]

Even BB plywood will cup definitely. Alot has to do with the glue they use too. When scrolled you release alot of the internal pressure so many times woods that have cupped can be used for scroll work so do not be too quick in discarding.