# Kiln Drying?



## djg (Dec 24, 2009)

I posted a question specifically about Red Elm on another thread and it got me to thinking, are there any species of wood that don't require kiln drying to achieve a stable product?

First comes to mind is Aromatic Red Cedar, but what about other soft woods? 
Soft Maple?
Hard Maple (seems kind of like a light wood)?
Again, Red Elm?
And I thought I read here something about Walnut not needing to be KD before use in a project? If this is wrong, does a D/H kiln bleach out the natural colors that you get when air drying only?
Hope you know what I mean.
Any others that might not require Kiln Drying?


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## Daren (Oct 14, 2006)

For exterior use, no species has to be kiln dried.

The advantages of kiln drying are obviously speed, and control. You really can't control "nature'' when air drying, it's either going to rain (100% rh) and the wood is not drying or it is hot/dry and the wood can dry too fast. I battle white oak for example trying to air dry it, it likes to surface check. No problems in the kiln.

You mentioned cedar and other softwoods. Some softwoods have to have the "pitch set" or the sap hardened to be able to work with it, air drying cannot do that. Walnut is a good example of a hardwood that can be used air dried...but it still has to acclimate to the space/conditions it will be in before use. You asked if a d/h kiln changes the color of walnut, no, that is why I use one-natural walnut is one of my favorite woods. Personally I would/do kiln dry all maples, again a control thing to avoid sticker stain and other problem light woods can have.

You asked about elm in this and another thread...below is a piece my dad made from air dried elm. It was never kiln dried. It did however sit in his shop that is heated/cooled and the humidity kept down year around for quite some time before he built with it.(so it was at kiln dried MC before he used it)

Even kiln dried wood goes back up to EMC (equilibrium moisture content) after sitting in an unconditioned space. We discussed it here, and the question was raised "do I even need to kiln dry ?" Maybe you will find some of this worth a read. http://www.woodworkingtalk.com/f26/storing-kiln-dried-wood-20014/ Do you have to kiln dry, not always...is it best/safest/fastest/etc to kiln dry, I think so.
















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## djg (Dec 24, 2009)

Thanks, and very nice book case by the way.


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## Daren (Oct 14, 2006)

And if you have not seen them here are some links for reading on air drying from our reference section...



Daren said:


> 3 links from a discussion in the "forestry and milling" section. dirtclod has a couple good ones http://www.chilternsaonb.org/downloads/publications/Air_Drying_of_Timber.pdf
> http://nrs.fs.fed.us/pubs/rp/rp_nc228.pdf
> 
> I had one bookmarked too. Between these 3 I reckon there is about all you need to know on the subject :smile:
> http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr117.pdf




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## wmodavis (Dec 26, 2010)

*Kiln Drying*

Daren's explanation is very much right on! Clear, concise and accurate. I wood (misspelled on purpose) clarify one thing he said. 

"(so it was at kiln dried MC before he used it)"

You can kiln dry wood to almost ANY MC. There is no actual MC attached to the term Kiln Dried. For example: structural lumber is dried in a kiln to reduce its shipping weight to a MC of around 15% - 19%. So the term KD for full clarity should be accompanied with an appropriate MC as applicable with the use.

That being said *djg*, a MC number can be implied and/or inferred from your context which is likely a wood project for indoor use. That implies a MC in the 6-8% MC range.


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