# Wood keeps warping!



## lateralus819 (Jul 22, 2012)

So I've made numerous items out of locally bought wood. 

Each instance the piece has moved in some way. 

I recently made a top for a box, and i went to my moms to see how it was doing, the top started to cup upwards. I've also a few pieces here that have either shrunk or start to twist! What is causing this? i'm buying the wood from a local yard that i presume is kiln dried and its only 30 minutes away so i dont think the change in location is that much of a factor. 

Is there anything i can do to prevent this? I'd like to start building guitars soon but with this i may have to resort to other venders such as ebay for wood..I purchased a 10 foot board of flamed maple off this guy on ebay and its held up great!


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## mdntrdr (Dec 22, 2009)

If your wood is moving it is because of changing moisture content.

Either gaining moisture or more likely drying. :smile:


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## GeorgeC (Jul 30, 2008)

lateralus819 said:


> So I've made numerous items out of locally bought wood.
> 
> Each instance the piece has moved in some way.
> 
> ...


What kind of wood are you buying?

You "presume" that it is kiln dried. You need to ask.

George


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## Dave Paine (May 30, 2012)

I also think it sounds like drying.

The box may only be 30 miles from the lumber yard, but it was likely in an unheated location. 

In your mothers it is presumable now in a house with heating, and likely lower humidity.

The top of the box could lose more humidity than the underside which would cause cupping.

As GeorgeC mentioned, you need to ask the lumber yard for what moisture content they aim for in drying the wood, whether air or kiln dried, each mill controls to different moisture content.

Another alternative is to invest in a moisture meter, especially if you want to make musical instruments.


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## woodnthings (Jan 24, 2009)

*wood warps in different ways*

It may cup, twist, bow, or kink. Like this:
 

*Wood warping* is a deviation from flatness as a result of stresses and shrinkage from the uneven drying of lumber.
The types of wood warping include:

*bow* : a warp along the length of the face
*crook*: a warp along the length of the edge
*kink*: a localized crook, often due to a knot
*cup*: a warp across the width of the face, in which the edges are higher or lower than the center
*twist*: a distortion in which the two ends do not lie on the same plane


Some warping has to do with drying for sure, but it may have to do with the grain direction and from where in the tree the board was sawn from. If you look at the end grain and see the growth rings are perpendicular to the width, it's probably quatersawn from the log and will have the least tendency to warp like this:
 
The boards on the right and left side outside edge will cup more. So look at the end grain and choose the boards with the straightest long grain on the surface and the most vertical end grain growth rings.


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## Steve Neul (Sep 2, 2011)

It sounds like you need to purchase a moisture content meter. Sometimes a lumber company will take shortcuts on drying the wood so its possible its still a little green. If you had a meter at least you could find out before you built something out of it. The meters are available at the box stores and are not very expensive.


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## lateralus819 (Jul 22, 2012)

Dave Paine said:


> I also think it sounds like drying.
> 
> The box may only be 30 miles from the lumber yard, but it was likely in an unheated location.
> 
> ...


Nope, the place i purchased it from stores it inside in a heated warehouse.


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## lateralus819 (Jul 22, 2012)

GeorgeC said:


> What kind of wood are you buying?
> 
> You "presume" that it is kiln dried. You need to ask.
> 
> George


It was maple and purpleheart.


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## lateralus819 (Jul 22, 2012)

Steve Neul said:


> It sounds like you need to purchase a moisture content meter. Sometimes a lumber company will take shortcuts on drying the wood so its possible its still a little green. If you had a meter at least you could find out before you built something out of it. The meters are available at the box stores and are not very expensive.


If i do get a meter, what do i do, wait till it hits a certain MC level?


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## Dave Paine (May 30, 2012)

lateralus819 said:


> If i do get a meter, what do i do, wait till it hits a certain MC level?


The meter will allow you to know the moisture content of the wood with relation to the shop.

Ideally the wood will be at the same moisture content as the shop. If it is not at the same moisture content, then there is the potential for some change to happen. The wood will either gain or loose moisture.

The meter will tell you the moisture content of the wood as a %.

You need a different instrument to tell you the relative humidity of the shop, and then a chart to convert the RH measure to a % moisture.

Sorry, but no single measurement for both wood and air, you need to do the conversion in order to compare.


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## cabinetman (Jul 5, 2007)

lateralus819 said:


> If i do get a meter, what do i do, wait till it hits a certain MC level?


It's a matter of letting the stock acclimate to your work area. KD lumber can still vary in moisture content. You could test for MC, and it could be different the next day.









 







.


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## Brian T. (Dec 19, 2012)

Quarter-sawn lumber is cut from 1/4 of the log. This maximizes yield from the log and mediates the mechanical properties of the drying wood in the radial and tangential planes.

Those center cut boards in the diagram above are not quarter-sawn. Sorry. What you're looking for in the end grain are diagonal growth rings, Best for furnishings and poor for carving. You might pay attention to the growth ring count. Anything less than 15/inch, give it up.

Kiln dried softwoods come out at maybe 24% MC. Air dried, under cover, outdoors, you can expect a final MC of 12 - 14% after about 1" per year (don't cook it in a closed-up tight shed, OK?) So a stickered pile of 2" planks will be good in the 3rd summer.

Buy the wood, sticker and stack the wood, close the door and walk away. Buy more wood and do it again and again. 
Kiln dried hardwoods may come out at 18% or less. . . .much more rapidly established stress in the rapid drying process.
The real kicker is that dry winter house air might be 4% and that spells trouble for fine woods such as you might find in a $5k guitar.

The other, entirely seperate, possible problem is that the wood you bought was cut from a tree that was growing on a slope. That creates tension wood in angoisperms and compression wood in conifers. Thsoe add, _unevenly_, to the upper and lower sides of the log/wood. That changes the drying a lot and the mechanical properties are likewise just as uneven.


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## GeorgeC (Jul 30, 2008)

"The other, entirely seperate, possible problem is that the wood you bought was cut from a tree that was growing on a slope. That creates tension wood in angoisperms and compression wood in conifers. Thsoe add, _unevenly_, to the upper and lower sides of the log/wood. That changes the drying a lot and the mechanical properties are likewise just as uneven"

Can you provide more details on this?

George


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## woodnthings (Jan 24, 2009)

*good link, despite the source name*

http://thecoachdiary.com/images/sawn-wood-definition
The diagrams show the differences, disregard the garbled text!





















As was said above, wood in tension called "reaction wood", and I said earlier, it depends on where in the tree the wood was taken from and if the tree was a leaner. All these factors as well as the moisture content of the wood and the humidity of the environment will affect wood movement. If wood dries too rapidly it will cup around the growth ring diameters, even in small pieces as thin as 1/2" thick cut from a green log. They will form almost perfect arcs. My guess is that's it's more of a wood grain/direction issue than a moisture issue, IF the warp is considerable.


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## TimPa (Jan 27, 2010)

besides moisture content, two more things to consider that will cause warping conditions. 

first - the method of drying - we have some (supposedly steam??) dried walnut, that warps as we pass it through the resaw, btw it reads 6% all around the board. so internal stress can be induced during the drying process. plan on ripping it narrow and re-gluing up. 

second - make sure you apply the same finishing process on both sides of the board panel. many new woodworkers apply more finish to the outside of the project, causing an imbalance in the moisture transfer rate of the wood surfaces (allowing it to warp)


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## Steve Neul (Sep 2, 2011)

lateralus819 said:


> If i do get a meter, what do i do, wait till it hits a certain MC level?


 I live near enough to Dallas there is multiple places I can buy wood. If someone is selling me green wood I return it and go to the next place. If that isn't an option you may need to rig some way to finish the drying process. You may need to make a homemade drykiln or you can sometimes if the wood just needs a little help enclose the wood air tight crate with a dehumidifier.


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## cabinetman (Jul 5, 2007)

In acclimating, there is a simple way to know if the wood is as dry as it's gonna get. Weigh the wood. When it gets to a lower weight, and maintains that weight...it's acclimated. Or, if the weight doesn't change...it's not picking up moisture or losing it.









 







.


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## Brian T. (Dec 19, 2012)

Quarter sawn: diagram #3 is out by 45 degrees. As shown, all boards are radially sawn, difficult to imagine the saw mill set up to do that. AND, that profile maximizes stress in both radial and tangential directions. BUT, if you're looking for wood with really dramatic figuring = that's it.

For wood carving, I expect the air-drying process to take approximately 1" per year to end up with a 
Moisture Content of 12 - 14%. Stickered and stacked, outdoors but under cover, 1 1/2" birch should be ready in 2 years.
Reaction wood: additional cell wall layers which are developed under stress. Clearly most common in branches but mainstems on slopes exhibit this as well. "Tension wood" develops on the upper sides of angiosperm/broad-leaf/hardwoods. "Compression wood" develops on the lower sides of conifer/softwood branches and stems.
While the chemistry is different and pulping processing is awkward, for wood working, the water content changes. The ratio of free water to bound water on that side is not the same as that found in the normal anatomy. Just adds another assymetrical stress force in drying.


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## lateralus819 (Jul 22, 2012)

TimPa said:


> besides moisture content, two more things to consider that will cause warping conditions.
> 
> first - the method of drying - we have some (supposedly steam??) dried walnut, that warps as we pass it through the resaw, btw it reads 6% all around the board. so internal stress can be induced during the drying process. plan on ripping it narrow and re-gluing up.
> 
> second - make sure you apply the same finishing process on both sides of the board panel. many new woodworkers apply more finish to the outside of the project, causing an imbalance in the moisture transfer rate of the wood surfaces (allowing it to warp)


Great point about the finish! I didnt finish the bottom of the lid, nor did i really concentrate on the backs of the other pieces as they weren't seen. I'll definitely take that into consideration next time thanks so much!

So i guess from now on, I'll try and pick the best lumber possible, and not use it immediately so it can acclimate? :thumbsup:


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## scsmith42 (Jan 24, 2011)

lateralus819 said:


> i'm buying the wood from a local yard that i presume is kiln dried



At a minimum, if the wood was kiln dried it has regained some significant moisture.


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## lateralus819 (Jul 22, 2012)

scsmith42 said:


> At a minimum, if the wood was kiln dried it has regained some significant moisture.


Im wondering if its a loss of moisture. The back panel, is a square with a rectangle cut out of it, with a mesh panel screwed on. The panel shrunk, causing the mesh to bow inwards, which would mean loss of water i.e. shrinking correct?


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## mdntrdr (Dec 22, 2009)

lateralus819 said:


> shrinking correct?



Correct.

You also need to finish all surfaces, inside/outside, front/back, etc. :smile:


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## commodore (Jan 14, 2013)

I agree "It's a matter of letting the stock acclimate to your work area" is the best practice.


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## scsmith42 (Jan 24, 2011)

lateralus819 said:


> Im wondering if its a loss of moisture. The back panel, is a square with a rectangle cut out of it, with a mesh panel screwed on. The panel shrunk, causing the mesh to bow inwards, which would mean loss of water i.e. shrinking correct?


Let me elaborate on my earlier comment.

Standard kiln operation dries hardwood lumber down to 6% - 8%. Based upon what you're experiencing, prior to the completion of your woodworking project the wood has picked up moisture well over and above the 6 - 8%. Whether this is occurring in the warehouse, your shop, or if it was not properly dried is the unknown.

After the piece is finished and installed in a climate controlled home, the wood dries back down to 6 - 8% and that's when your movement is occurring.

If the wood had been maintained at 6 - 8% after it came out of the kiln, you wouldn't be experiencing any problems.


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## against_the_grain (Aug 15, 2010)

A kiln is an entirely different business than that of a lumber yard. I purchase hardwood directly from the kiln.

This kiln does all the drying for a particular lumber yard.

In fact, the lumberyard owns all of the kiln's lumber inventory, but not the
kiln operation itself.

I'm guessing there is a price mark-up from the kiln to the lumberyard also. Find out if there are any kilns in your area . They usually sell retail as well as wholesale.

Many woodworking shops and barns are unheated and not dehumidified. Thus they will introduce moisture into the wood.

Also pay particular attention how you finish your projects. If you only apply finish to one side of a board, it will release moisture unevenly out the unfinished side and trap moisture in the finished side which acts like a moisture barrier. This will cause cupping and warping.

As others have stated. You should purchase a moisture meter for the lumber and monitor/control the humidity in your shop or where you store your lumber.

The wood will still try to aclimate to whatever its final home is going to be.So some movement is to be expected. The key is to avoid drastic changes in humidity content from the time the lumber is acquired, to the its final home.


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