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I have offcuts of Macrocarpa that I'd like to use instead of keeping them there doing nothing useful. I acquired some Macrocarpa wood that is still wet, it seems that it has been cut recently, I've had it for a month now myself. I was wondering if:

  • I can use the wet wood to create a wall hanging (12 by 12 inches), it will be a join of three 4 inch wide pieces. would something happen to it over time as it dries such as break apart?
  • I can use a mix of wood (new and dry) to achieve this?
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In short, don't do it. Drying wood is subject to a lot of shrinkage and at different rates depending upon whether you measure across the grain rings (radial) or with them (tangential). (There is very little shrinkage in the length). The overall amount will differ depending upon the species (I could not find actual figures for Cypress but it should be similar to other soft woods), how wet it is and the relative humidity, but it could easily be in the 10% range. In addition the tangential shrinkage can easily be double the radial. So, all in all , there is a lot of movement during the drying process. All of this adds up to a lot of internal stress in the wood. It is why you see cross sections of tree trunks with large gaps like pieces of pie that have been removed. The wood is shrinking rapidly and the stress is too much. It is also why you see splits at the edges of drying lumber. These cracks occur as a result of the differences in the shrinkage rates between wood at the ends where evaporation is occurring at a higher rate than further towards the middle of the board where the evaporation and shrinkage is slower. All wood must be dried to achieve any dimensional stability. The wood may be kiln dried or air dried. Air drying takes a lot of time, as a rule of thumb allow 1 year per inch of thickness.

The key issue for your project, other than the fact that the whole thing will shrink is that each board will shrink at different rates depending upon grain direction across the boards. Since the project is small it is possible that the wood and glue (screws?) can hold up to the stress if the boards are all oriented exactly the same and have small areas of contact, but it is likely that the wood will split near where the boards are attached. As to mixing the green and dried wood, the dried wood will not shrink anywhere near as much as the green wood and you are almost guaranteed to have problems.

  • I guess its not a very good idea after all, I wanted to use just glue to hold the boards together and I dont want it to break apart or cracks to appear later on. – OKAN Apr 20 '16 at 23:35
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In general you don't want to mix dried wood with green wood (any wood from freshly cut to not fully dried is 'green' to some extent). However there are specific areas in woodworking where green wood is mixed with dry, so it's not an absolute don't do it.

Smaller projects are more forgiving with regards to wood movement because the total size of the movements is small. Since you're looking at making a piece only 12" square (30.5cm) with only a few pieces 4" (10.2cm) wide there is a limit to how much shrinkage the green boards will go through.

And anyway, for a non-structural project for yourself I don't see why you can't at least try what you've planned. Do note that shrinkage is not the only thing that occurs as green wood air-dries, it can warp and crack too. If the drying of the green portions does cause certain problems you can see them firsthand, which many woodworkers don't ever get a chance to see.

And who knows? You might actually like what happens, these days people make use of non-perfect wood all the time for its character.

  • these days people make use of non-perfect wood all the time for its character. Damn straight – Matt Apr 15 '16 at 11:54
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Simply would not, boards could shrink and warp. You could use them and next day everything is done for. The only thing you could do (MAYBE) is cutting all the boards into 3 inch stripes and taking a glue joint router bit (I would use a finger joint) and glue the board, which should resist warping of the board. But it is better to let the wood dry before using.

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Despite all the DON'T DO IT naysayers, if you're looking to create an artistic wall hanging piece, I'd say go for it!

You'll have to make adaptations to your design to accommodate the shrinkage that will happen as the pieces dry, but I think it could be handled, perhaps by a single pocket screw holding each pair of boards together. This would give you a dynamic, living (dying? drying?) piece of art that would change over the next couple of years, until it finally reached room humidity. As with any art piece, it might come out very nicely or it might be utter rubbish, but if you go into it knowing and accepting that, you might just end up with something you really like.

As a side note, wet and dry wood are commonly used in making small wagon wheels. A dry spoke is fitted through a just big enough hole in a piece of green wood that acts as the other spoke. As the green wood drys, it shrinks, locking the dry spoke very tightly in place without any fasteners.

  • All the naysayers, all two of them ;-) – Graphus supports Monica Apr 19 '16 at 11:57
  • Well, there are only two who spoke up here. There are many who were quiet and others who don't frequent this locale. ;) Oh, and there were three other answers saying "don't"! – FreeMan Apr 19 '16 at 12:19
  • "Oh, and there were three other answers saying "don't"!" That was my point, there weren't. One of the replies is mine and only the first part of the first sentence makes it sound like I was saying don't do it. – Graphus supports Monica Apr 19 '16 at 17:22

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