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Author Topic: Dry wood...how long before getting back it's humidity???  (Read 3515 times)

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Offline roger 4400

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Dry wood...how long before getting back it's humidity???
« on: November 29, 2012, 11:59:42 AM »
     Hi everyone. I'm planing some black cherry that was seasoned and dry in my basement for a few years (6 to 8 deg,now)to make some handrail. My basement is heated (wood stove) but I work in my garage and I only light the stove when I'm working in it. Today for an example it was 40 deg. when I started and 65 when I stopped after heating it for a few hours.  Of course the garage is more humid than the house .
I would like to know if I can let my dry wood for a few nights in the garage without seeing the wood taking back humidity? Do I have to take back the dry wood into the house every night (what I did today) ? Next thing I will glue the sticks together and then milled them.......and the next step will be some black walnut handrail ....so I do not want to mess everything up. Thank you. Roger
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Offline Ianab

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Re: Dry wood...how long before getting back it's humidity???
« Reply #1 on: November 29, 2012, 02:01:32 PM »
Depends on species and temperature, but it can change a noticeable amount in only 24 hours.

Just try leaving a wide board flat on the bench in the more humid shop. Damp air can get at one side, not the other, and it can cup overnight. Not a big problem, turn it over and next day it will have evened out again.

But that's the sort of thing you have to watch for. Getting a board nice and flat, then coming in next day and it's not, because the moisture is changing unevenly. Gets annoying quick.

As an experiment I oven dried a sample board, from 14% (shed) down to ~0%. Then left it on  my desk, and weighed it each day to check the MC. After about 2 weeks it was up to 10%, and settled around 12% eventually.

Now the change may not be enough to to mess up what you are doing, especially if you stack the boards carefully when you leave them, so any change is going to be even. It's when one side gains moisture more than the other that things get interesting.

Ian
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Offline Den Socling

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Re: Dry wood...how long before getting back it's humidity???
« Reply #2 on: November 29, 2012, 04:43:25 PM »
Since you are gluing, you are going to want the variation in MC between pieces to be minimum. Not all pieces are going to gain MC equally. Therefore, I would say that the pieces should be returned to where they were equalized.

Offline GeneWengert-WoodDoc

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Re: Dry wood...how long before getting back it's humidity???
« Reply #3 on: November 29, 2012, 09:07:11 PM »
Cover the pile with plastic wrap really well (all six sides) and then you can leave it in the garage without concern.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline roger 4400

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Re: Dry wood...how long before getting back it's humidity???
« Reply #4 on: November 30, 2012, 08:24:48 AM »
Thank you for sharing your so precious experience. Roger
Baker 18hd sawmill, massey Ferguson 1643, Farmi winch, mini forwarder, Honda foreman 400, f-250, many wood working tools, 200 acres wooden lots,6 kids and a lovely and a comprehensive wife...and now a Metavic 1150 m14 log loader so my tractor is a forwarder now

Offline Okrafarmer

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Re: Dry wood...how long before getting back it's humidity???
« Reply #5 on: February 08, 2013, 12:30:42 AM »
So-- if I have some lumber kiln-dried (as I have) and it sits around in a somewhat humid environment for a few months taking on moisture-- what do I tell people when they come to buy kd lumber from me?
He that dwelleth in the secret place of the most High shall abide under the shadow of the Almighty. Psalm 91:1

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Online beenthere

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Re: Dry wood...how long before getting back it's humidity???
« Reply #6 on: February 08, 2013, 12:33:38 AM »
The truth.  ;)
south central Wisconsin
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Offline tyb525

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Re: Dry wood...how long before getting back it's humidity???
« Reply #7 on: February 08, 2013, 12:43:09 AM »
 Which is why kd lumber us overrated imo, unless you have bugs to kill, or pitch to set in pine. I say build it so the wood can move slightly as humidity changes, we all know it changes anyways even in a house with a/c and heat.

And another tip, don't glue up a panel  until you actually need it, because it will warp if it sits too long

And at the end of the day, don't lay a  board flat on the backbench, stand it up on edge or end.
LT10G10, Stihl 038 Magnum, many woodworking tools. Currently a farm service applicator, trying to find time to saw!

Offline Okrafarmer

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Re: Dry wood...how long before getting back it's humidity???
« Reply #8 on: February 08, 2013, 08:34:08 AM »
The truth.  ;)
;) Yes, I know that, and that's what I do.  ;D
It just seems a little sad to have to point it out. I had a guy come in the other day who felt the wood and told me it had really taken on moisture, and he was going to have to put it in his little kiln to dry it out again. Really not what I wanted to hear as I sold my kiln dried lumber.  :( He did buy some, though.

Tyb, there are always bugs to kill, especially in ambrosia maple!

I should be moving the lumber out of the leaky building soon into my new facility. The new facility should not be having the constant dripping from leaky roof and the flooding of the floor from water rushing under the door, that I am experiencing where the lumber is now. But it is not climate controlled, and the dampness that is South Carolina permeates everything.
He that dwelleth in the secret place of the most High shall abide under the shadow of the Almighty. Psalm 91:1

Operating a 2020 Woodmizer LT35 hydraulic for Wagner Farms, Dacusville, SC

Looking for the return of the Lord!

Online beenthere

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Re: Dry wood...how long before getting back it's humidity???
« Reply #9 on: February 08, 2013, 10:12:48 AM »
Maybe a plan to have the lumber on air drying pile (stickered) and if kiln drying needed, do it just before the buyer gets it (pick-up or delivered). Would mean selling by the kiln charge.
Otherwise, hard to have kiln-dried lumber for sale at a later date.

Hope it all works out for ya.
south central Wisconsin
 It may be that my sole purpose in life is simply to serve as a warning to others

Offline Okrafarmer

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Re: Dry wood...how long before getting back it's humidity???
« Reply #10 on: February 09, 2013, 11:04:28 AM »
Yes, that's the problem. I'm not a wholesaler, I'm a retailer. People must be able to pick through the wood and pick out the individual boards they want. Sometimes they may leave with only one board.

Thankfully, I just sold some more of my kd lumber yesterday, so it is moving. I'm in a transition time right now, preparing to move to my new location, and with other work going on, I hadn't been promoting the retail as much. Soon, I hope to have it all straightened out. I hope two months from now, I'll be more on track.
He that dwelleth in the secret place of the most High shall abide under the shadow of the Almighty. Psalm 91:1

Operating a 2020 Woodmizer LT35 hydraulic for Wagner Farms, Dacusville, SC

Looking for the return of the Lord!

Offline jimF

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Re: Dry wood...how long before getting back it's humidity???
« Reply #11 on: February 09, 2013, 11:28:14 AM »
If the lumber is intended for exterior projects, no it does not need to be kiln dried.  But all lumber intended for interior use should be kiln dried.  Unless it is for the basement. With air conditioning and heating there is little MC gain while in use.  What there is, is cyclic within a small range and with hysteresis over time even less MC gain.  If the shop is half way controlled, there will be little gain during construction.  If the boards stacked horizontal are well dried they should not gain nor lose much during construction.
If you have a shop that is exposed to exterior conditions maybe kiln dry it to 1-2 MC% higher then normal but it should still be more than air dried.  In the book I cover glued up panels so I will not repeat it here.
Another reason I push kiln dried lumber is the general attitude people apply to kiln dried verse air-dried.  Air-dried material is usually considered storage/second rate.  As to kiln dried material, people usually put more care into it. Generally, not always, for there are exceptions, the more investment one puts into something, the more care they will take in maintaining the final product.

Offline Tree Feller

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Re: Dry wood...how long before getting back it's humidity???
« Reply #12 on: February 09, 2013, 06:26:10 PM »
Jim,

I pretty much agree with everything you wrote except maybe about the air-dried lumber being considered second-rate. That is probably true for the general public but those seeking out hand built, custom furniture, I think are a little better informed. For them, pieces made from air-dried lumber might be more desireable than kiln-dried.

Other than "workability", there is little reason not to kiln dry lumber for indoor use. The plusses outweigh the minuses significantly. Even the workability issue is moot unless one is predominantly using hand tools and even then, I think it would take a long time to develop a feel for the difference in working kiln dried vs air dried lumber.

Krenov used air dried lumber but it also stood in his shop acclimating for up to seven years prior to him working it. I expect it was as dry as it ever needed to be by then.

Cody

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Offline Den Socling

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Re: Dry wood...how long before getting back it's humidity???
« Reply #13 on: February 09, 2013, 07:07:08 PM »
If you are going to air dry for 7 years, I'd say there is zero problems. If you are going to cut and dry a couple months before using, I think it should be sterilized in a kiln. And not many people are not going to be willing to air dry for years.

Offline Okrafarmer

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Re: Dry wood...how long before getting back it's humidity???
« Reply #14 on: February 09, 2013, 09:39:39 PM »
I really think it's a good idea to kill the bugs somehow. Maybe you could pipe exhaust fumes into a building with green lumber and kill the bugs that way.  ::)
He that dwelleth in the secret place of the most High shall abide under the shadow of the Almighty. Psalm 91:1

Operating a 2020 Woodmizer LT35 hydraulic for Wagner Farms, Dacusville, SC

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Offline jimF

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Re: Dry wood...how long before getting back it's humidity???
« Reply #15 on: February 10, 2013, 11:11:00 AM »
When one reads my post below, I hope they read the word "attitude" as Treefeller alluded to when he said "probably true for the general public ".  The care or effort that is often put into the product often is less with with air dried.  Then again I have seen kiln dried lumber with MC samples hanging next to it sitting over puddles of water.
As far as the possibilities of the quality of the product, I have air dried purposely for some projects because of the quantity and taken the objects indoor to finish off.  Also, as Treefeller mentions workability, kiln dried material can have problems but that can be avoided by being careful of how low the EMC the lumber is exposed to.

Each system of drying can achieve high quality lumber, but it is the operator's attitude and knowledge that determines the outcome.  And the resources the operator has that may limit his choices of which system he picks.

Offline tyb525

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Re: Dry wood...how long before getting back it's humidity???
« Reply #16 on: February 10, 2013, 12:02:15 PM »
How often is lumber kept in kiln-dry conditions once removed from the kiln? Once it gains a few % it is essentially the same as air-dried lumber isn't it? And if the kiln operator was careless and case-hardened the lumber without knowing, is it still better than air dried at that point? What about furniture an older house that isn't airtight? I've noticed flooring manufacturers reccommend letting kiln-dried flooring acclimate for up to two weeks before installing. Why is that, if it is already dry?
LT10G10, Stihl 038 Magnum, many woodworking tools. Currently a farm service applicator, trying to find time to saw!

Offline Tree Feller

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Re: Dry wood...how long before getting back it's humidity???
« Reply #17 on: February 10, 2013, 01:50:10 PM »
How often is lumber kept in kiln-dry conditions once removed from the kiln?


Quite often. A RH of 35% will keep the lumber at 7% MC indefinitely. Even in an unheated/air conditioned building, the RH is lower than it is outside. That's why you see kiln-dried construction lumber stacked in open sheds yet hardwoods are almost invariably kept in an enclosed building. There is also the hysteresis effect that Jim F mentioned above which limits the moisture the wood will regain.

Once it gains a few % it is essentially the same as air-dried lumber isn't it?

No. It takes a long time for wood to regain moisture all the way to the core. That's why it is heated during kiln drying...to facilitate the movement of inner moisture to the surface. Again, there is that hysteresis effect. Kiln dried wood will never return to the average moisture content of around 12% but will remain somewhat drier


And if the kiln operator was careless and case-hardened the lumber without knowing, is it still better than air dried at that point?

There is probably a greater chance of degrading lumber by air drying than there is by kiln drying because air drying is virtually an uncontrolled process. One dry, windy day, especially early in the drying cycle can ruin a stack of lumber.

What about furniture an older house that isn't airtight? I've noticed flooring manufacturers reccommend letting kiln-dried flooring acclimate for up to two weeks before installing. Why is that, if it is already dry?

No matter the drying method, wood will eventually reach EMC with it's environment. A wood floor is essentially one huge panel and tangential movement can be significant. Letting the wood acclimate before securing it in place is only good practice.

Ideally, furniture would be built with wood that is in the middle of the EMC for the home. Even a drafty home is heated during the colder months. When dry, cold, winter air is heated inside, the RH drops significantly. The wood will begin to shrink. Conversely, during the summer months, the humidity is generally higher. Building with the wood in the middle of the humidity range for the home lets it see the least amount of total movement in any season.

One can definitely build quality furniture with air-dried lumber. It's done every day all across the country. However, limiting the amount of movement the finished piece will see is not only good practice but the furniture will last much longer.

Kiln drying hardwoods costs money. If it wasn't beneficial, it simply wouldn't be done.
Cody

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Re: Dry wood...how long before getting back it's humidity???
« Reply #18 on: February 10, 2013, 05:11:06 PM »
I am glad someone mentioned that air drying can be more risky than kiln drying.  And as for casehardening, all dried lumber has casehardening to some degree if not conditioned. What ever drying system one chooses, they need to know the benefits and risks and manage those risks, then they can achieve quality lumber.

Offline tyb525

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Re: Dry wood...how long before getting back it's humidity???
« Reply #19 on: February 10, 2013, 06:07:08 PM »
All said and done, I wouldn't mind having a kiln, even if it is just to speed up the drying process, and kill bugs to ease the buyer's mind.
LT10G10, Stihl 038 Magnum, many woodworking tools. Currently a farm service applicator, trying to find time to saw!


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