air dried vrs kiln dried?

[larry merlau]

i have seen several of posts refering to air dried lumber rather than kiln. which i have used some of each and would like to hear the pros and cons from some of you. also the time needed to be dry enough by air drying under proper conditions. thanks for your info. larry

[Bob Smalser]

Depends on the wood and what you want out of it.

In general, airdried stock has better color and is more resilient. Some woods, like Alder however, acquire better color in a kiln....but for bending stock in oak, beech and cedar it's almost imperitive that it be airdried. Many logs differ in their moisture content...some like cedar are extreme...some logs 30pct and some 60pct...so when mixed together in the kiln the 30pct logs will invariably be overcooked and brittle.

The trick in drying is to do it slow...painted ends, stacked stickered and covered...generally for 1 drying season per inch of thickness. That will take it in most areas to 18-20pct, where it becomes safe to move it indoors for a few weeks to bring it tot he 10pct range for furniture or trim. Once the wood dries to its equilibrium moisture content...22-25pct or so...the severe shrinking/warping is over, the wood is more stable and properly-made stacks aren't as important.

All-in-all, green stock is so much cheaper than kilned stock...especially from local sawyers as opposed to the big chain stores...that it is well worth it to buy in quantity and dry yourself.

Here's a good 5-yr-old softwood stack....for hardwoods, extend the upper boards outward to insure the board ends are shaded...and never use plastic, always tar paper or something else that doesn't sweat...and always keep the sides open. Rain hurts nothing so long as the wood can breathe. Note the stickered are lined up, how straight the boards have dried and the sawdust on board ends exposed to the sun.

http://pic3.picturetrail.com/VOL12/1104763/3075040/31637402.jpg

[Donnie Raines]

First of all, the numbers that can be thrown around vary greatly with where you are located(humidity and the like). Also important is how the boards are stored.

Certain species will have a deeper color when air dried..Walnut and Cherry being two of the best examples I can think of. Walnut will have a more purplish hue to it when air dried(rather then a creamy/brown color when kiln dried). Cherry will also be more dark in color when air dried. Keeping in mind that the color is also effected by the age of the tree as well as the area of the country the tree grew(cooler parts of the country will normaly yeild a better color of lumber(cherry and maple being good examples).

I have never had any problems useing air dried lumber. In my neck of the woods(Ohio), kiln dried lumber will fall some where between 6-9 percent asfter being dried and then being strack away to await a project. Air dried lumber will be in the 9-12 percent area..again in my part of the country. The key to succesful air dried lumber useage is making sure that you have good air flow around the boards while they are in limbo for a project. A good rule of thumb for "how long" to wait prior to useing air dried lumber is 1 year - 1 inch. Again, the more air flow the better. Use a moisture meter to check the content out prior to useing and or buying air dried lumber.

Kiln dried lumber is the more common way to buy lumber these days. However, if the person doing the drying does not do the job right, it could ruin the entire stack. If the lumber is dried to quickly the boards will cup and twist(a long with crack and check). Also, they could get case harding(where the outside of the lumber is dried, while the inside is still to wet and wil cause serious issues down the road(if not when you are working with it). On the other hand, if the drying process is done correctly, you will be working with nice lumber(at a very good price..if you buy from a mill) in a very short period of time(factorin 1-2 months to let the boards air dry, then 2-3 weeks in the kiln..depending on where you go). So, you could have usebale lumber inside a 2 month period VS at least one year with air dried.

So did I confuse you...... :rolleyes:


Donnie Raines

[Robert Ducharme]

Let us get down to specifics - I have that english walnut I posted in the roadtrip thread. I have not yet decided what to do with the wood (many, many projects). So I was thinking of cutting it to 8/4 and either air or kiln drying it. Since I have many things to do before starting with it, from this thread it sounds like I could air dry it with no problems.

Now for the questions and procedures:

Let us say I cut it with both 4/4 and 8/4.

Should they be stacked in the same stack?
Should the wood ever be moved around once the drying process starts? Do I move it around to check the moisture of the inner boards?
Are you saying to place a tarp over the top extended out to provide shade from the sun?
Can I air dry it in my workshop (volumn in building is around 100,000 cu feet) instead of having it outside. The door will be open in the summer enough that the humidity levels will be pretty standard/low.
Do I use a moisture meter to check level or do by weight?
Why "pond" things - does that mean place in water and let it sit there for a year? What does that do?
With the grafted piece of wood I have, what should I do? Or is it worth waiting until it is cut to ask that advice?
Is it better to cut figured wood thinner or thicker?
Is there any constraint on how wide / tall the stack should or should not be?
How much weight should be placed on the very top above the stickers?

[Bob Smalser]

Put the 8/4 on the bottom...it'll be ready last, it'll stabilize the stack, and you want it to dry the slowest with the most shade.

Once stacked and stickered, don't move it until it reaches equilibrium moisture content.

Make the stack no wider than 4', and you won't have to worry about the M/C of inner boards.

You don't really need a moisture meter...the oven works just dandy. You're only gonna check it once a year, anyway.

No plastic tarps...use utility wood to make a shade canopy or use the top couple walnut board decks...then use tarpaper, Tyvek or just scrap boards. You are protecting it from the sun, not the rain.

Don't bring inside until it stabilizes outside. Otherwise you'll dry it too fast with checking and unequal moisture distribution. The 8/4 will need two drying seasons outdoors. Ponding in water merely slows down the drying, although the wood still dries under water by losing moisture from within the cells....useful for highly-figured wood prone to checking, like maple "music" wood.

Figured wood is best cut to 5/4 or thicker to allow flattening after drying.

Some advocate weighting the stacks for walnut and oak. I don't agree...if the wood's gonna move, it's gonna move for a variety of reasons - no puny concrete blocks will stop it...but it won't hurt if you want to do it.

Best to stack on a hillside for airflow. Pallets make a decent base if you get them nice and flat with solid blocking. Use kiln dried lath or plywood strips for stickers...green stickers will result in sticker stain.

A stack 4-5' wide and as tall as you like it will work...but taller stacks are more difficult to shade.

Again, no plastic or tin roofing or anything else that sweats.

[Robert Ducharme]

The comment about drying too fast indoors in my workshop makes me wonder whether it will try to dry too fast outdoors. It is realllllllly dry here in the mountains where I live - real low moisture content in the air. Should I be concerned with that?

What do you mean the oven for checking moisture content - as you can tell, you are conversing with a REAL novice.

Being as this is walnut, should I be putting some insect repellant on it? I think we mostly just have pine beatles up here but may be other nefarious insects. If so, how is it placed on/around?

[Bob Smalser]

Once the bark is off, insects are rarely a problem....but throw some Diazinon under the stack if you like. Carpenter ants don't like stickers, and most powder post and all ambrosia beetles require bark.

It's just as dry here in W. WA from Jul-Oct as it is where you are...the wood will dry to well under 10 pct...slow the drying down by milling the boards in early winter when you can, paint the ends with parafin wax or water-emulsion tar (Henry's at Home Depot) and keep it shaded. You likely won't have any special problems...remember 50pct of the drying time is at night with higher humidity and dew.

Tar is cheap, effective, but adds a step....chop those tarred ends off before running it through the planer. The commecial product for end paints (wax) is called Anchor Seal....but it's spendy to ship and tar in a water emulsion dries like paint and works well.

To check M/C, get a postage scale, weigh a chunk of the wood off the stack, then dry that wood in a slow oven until it no longer loses any more weight. The difference between the starting and ending weights is your pct M/C.

These are FOHC DF keel timbers and beams 24-27' long with no checking after 5 years:

http://pic3.picturetrail.com/VOL12/1104763/3075040/31637369.jpg

And here is figured 5/4 maple stacked "in the bolle" with considerable end checking, in spite of the cover (removed for the pic)...that wood woulda benefited from ponding or a water spray on dry days for the first year.

http://pic3.picturetrail.com/VOL12/1104763/3075040/31637395.jpg

[Robert Ducharme]

There will be a book on this when we are done :)

I was only planning on cutting the logs now, then drying the wood, then doing the final milling of the wood when I started using it.

I have placed a sealit on the ends (like anchor-seal) of the logs. How long do I have before I must get the logs cut and the bark off?

Do I cut sometime this next month, let them dry and then mill the boards partially this winter and then let dry some more? Or did you use the word mill to mean cut the logs this winter?

[Bob Smalser]

Your logs need to be either milled or debarked ASAP before insects get into the cambium layer. In winter you don't have to worry about that.

Logs harvested and milled in winter dry slowly int he winter snow and spring rains and stand the summer better w/o checking.

Walnut dries pretty well...unlike maple...do the above and you should be OK. Cherry doesn't dry as well as walnut, but isn't as bad as maple.

[Robert Ducharme]

Thanks alot for the info. Also, thanks Larry for the highjack of the thread. :)

[Jim Becker]

To Larry's original question, I use air-dried lumber "all the time", both from our property and from my local supplier. Only material bought for figure, etc., is generally kiln dried, just because that's the way it comes. I'm fine with either, but I'll take air-dried walnut over KD any day, especially if the KD was done with steam. That really affects the color and I don't like to lose the rich greens and purples in the walnut that give it character.

[Paul Downes]

Larry, go to www.woodweb.com and check out the sawing and drying forum. There is a lot of technical information in their knowledge base as well. Also they have lots of solar kiln designs listed on this site. I myself am planning to build a small solar kiln to finish drying air dried lumber. I pulled a hard maple board out of the barn rafters the other day and found powder post beetle larvae trying to make a collander. I'm going to sticker this wood outside wraped up in a dark brown tarp and try to get the temps up over 130 for a week to kill these nasty little critters. Good thing I've got some strapping sons to do the work as there is a lot of lumber stored in the rafters.

[Bob Smalser]

Larry, go to www.woodweb.com and check out the sawing and drying forum. There is a lot of technical information in their knowledge base as well. Also they have lots of solar kiln designs listed on this site. I myself am planning to build a small solar kiln to finish drying air dried lumber. I pulled a hard maple board out of the barn rafters the other day and found powder post beetle larvae trying to make a collander. I'm going to sticker this wood outside wraped up in a dark brown tarp and try to get the temps up over 130 for a week to kill these nasty little critters. Good thing I've got some strapping sons to do the work as there is a lot of lumber stored in the rafters.

Woodweb is a truly great resource.

Just keep in mind that the professional posters and advisors there are largely also in the commercial kiln business...many have little or no experience air drying...and the answers are sometimes skewed accordingly.

I doubt you'll get the 130 degrees you need using black plastic...but give it a try. If the beetles have attacked the heartwood of dry lumber as opposed to just the sapwood while the bark was still on...then you do have a serious infestation problem and I'd make real sure all those larvae were dead by isolating the affected boards and watching them for frass (sawdust-saliva droppings) for another entire season.