How to build a drying kiln?

[Rob Will]

So let's say you live on a farm and your neighbor has a Woodmizer. Well over the years you have accumulated various hardwoods mostly cut to 8' lengths and carefully stick stacked in an un-heated barn. Some of this wood is 2.5" thick cherry and hard maple. Some was cut recently but no big hurry to use it.

Does this wood need to be kiln dried?
and if so.....
What is the best way to construct a small kiln?
What is the proper temperature range?
How much time?
How dry is dry?
Do you use a dehumidifier or temperature alone?
Anybody ever build a vacuum kiln out of an old tank?.....or is this overkill?
How about an old insulated truck body?

Thanks for any ideas you folks care to share.

Rob

[Jim Becker]

You do not "need" to kiln dry the lumber. Folks have been using air-dried lumber for thousands of years...including "right now"...and if it's done correctly, it's every bit as nice as kiln dried. Some species, such as walnut, are actually prettier when air-dried since the lumber folks tend to "steam" it for higher yield. Steaming makes the sapwood darker, but also turns the whole board the same ruddy and undistinguished brown color...air dried walnut has a lot of wonderful browns, greens, purples, etc., in it.

That said, a dehumidification kiln or a solar kiln is relatively easy to build. There have been a number of articles on it over the years, both online and in print. A google search should get you there. And yes, leveraging an old truck body or container can be a "quick start" to your own kiln...

BTW, air drying is best done outdoors where there is free air flow through your pile, at least for the first year or so. You only need to cover the top with a sloped "lid" to insure that there is no standing water on the pile. Otherwise, rain and snow don't really matter and there should be nothing to restrict the flow of air through the pile. I work mostly with air-dried stock, both from our property and purchased and have never been sorry to do so.

[Mike Wilkins]

Go to the nearest bookstore such as Barnes & Noble and get a copy of the latest issue of Woodwork magazine. There is an article describing how to make a small drying kiln. The author used plywood, a small dehumidifier and a moisture meter for monitoring the drying process.
Seems like a great way to start drying small quantities of lumber after a period of air drying.

[Lee DeRaud]

Has anybody tried an "in-between" method? I'm thinking in terms of my south-facing side yard: sticker-and-stack and cover with a "tent" of black plastic sheeting to hold the heat in.

[Ian Abraham]

<TABLE class=tborder cellSpacing=1 cellPadding=6 width="100%" align=center border=0><TBODY><TR title="Post 348024" vAlign=top><TD class=alt2>Has anybody tried an "in-between" method? I'm thinking in terms of my south-facing side yard: sticker-and-stack and cover with a "tent" of black plastic sheeting to hold the heat in.</TD></TR><TR><TD class=thead colSpan=2></TD></TR></TBODY></TABLE>

Sounds like a good way to grow mushrooms :o
You need at least some air flow to carry the evaporated water away, otherwise you have created a hothouse / sauna.

Back to the original post.
If the wood has been air drying for a couple of years it will have a moisture content that depends on your local climate / season. Probably 10-15% depending where you live. If you just bring the wood inside and sticker it in a heated / aircon area it will dry out to around 8% in a month or so. For small amounts you can build a baby 'kiln' out of a ply box with a box fan and light bulbs for heat. Sticker the wood in there for a week or 2 and it will be fully dried. If you have an attic thats also a good place to finish drying wood. The only trick is to get the wood dried down to the moisture content where it's going to be used. How you get there doesn't really matter. (apart from setting pitch in pine and killing insects which are extra bonus of kiln dried wood)

If you want to dry bigger amounts or dry green wood quicker then a solar kiln is the cheapest / simplest option for small scale drying. Time taken depends on the sun / season but the results seem very good and setup costs can be very low, especially if you have cheap wood and can salvage some glass and insulation.

Small commercial dehumidifier kilns can be build using an old refridgerated container or truck body as a chamber, faster and more relaible timing than solar, but you are getting into quite a few dollars to set up and really need to be drying commercially to make it worthwhile.

Vacumn kilns are probably the most expensive and technical, both in terms of the chamber, the pumps and the heating thats needed. They dry like magic, especially with wood that are otherwise difficult to dry. But cost and complexity put most small scale operators off, especially when solar and DH is so much simpler.

My advise, if the wood is well airdried and you aren't in a hurry then bring it inside for a bit of extra drying and then go for it. You dont NEED a kiln if you have time and space.

Cheers

Ian

[lou sansone]

rob
spend some time on the sawing and drying forum at woodweb and you will gain a wealth of information. Although I use all air dried wood, there are applications that really benefit from kiln drying. Two instances that I can think of are setting pitch in pine and killing power post beatles.

lou

[Frank Fusco]

We have a professional solar kiln in my area. It uses plastic and some simple fans to move air. I don't know that the (clear) plastic holds heat in. I believe it does have a capture effect. The inside temp is always 75 degrees higher than outside on relatively sunny days, even on gloomy days it is quite warm in there. Works. I'm going to build a simple frame with clear plastic and a small fan.

[Rob Will]

Lots of good ideas here.
Thanks gents,
Rob

[Travis Johnson]

Hey Rob,

Have you ever checked out the Forestry Forum website? They are a great resource as they earn their bread and butter with their sawmills and solar kilns. In fact they have a section dedicated to "Processing and Drying lumber" and I know they have had a lot of questions and answers regarding small solar kilns and dehumidification kilns.

You will have to become a member to post a question, but great people and even better real world, cost effective answers. In any case, you might want to try them out. Here is the link:

xxxxxxxxxxxxxxxxx

Travis

[Reg Mitchell]

Hey Rob,

Have you ever checked out the Forestry Forum website? They are a great resource as they earn their bread and butter with their sawmills and solar kilns. In fact they have a section dedicated to "Processing and Drying lumber" and I know they have had a lot of questions and answers regarding small solar kilns and dehumidification kilns.

You will have to become a member to post a question, but great people and even better real world, cost effective answers. In any case, you might want to try them out. Here is the link:

xxxxxxxxxxxxxxxxx

Travis
Travis would you PM me that link...some RULE took it
Thanks

[Rob Will]

Travis,
Thanks for the info, it sure would be nice if the moderator was not so insecure and I could actually see what you are talking about. Posting a link in the context of sharing information directly relating to the particular thread is often quite helpful. It happens all the time.

Thanks for trying,
Rob

[Jim Becker]

Rob, the Terms Of Service (http://www.sawmillcreek.org/terms.php) (Section E, entry 3) specifically doesn't allow direct links to other forums, public or private, and Ken noted that in his edit of Travis' message. There are always creative ways to accomplish the reference to something on another forum without a direct link. Keith has explained a number of times that the membership, when SMC was established, decided to disallow these links because we have members under age 18 and have no control over the content, language, etc., allowed on other forums.

[Paul Downes]

Rob, google for woodweb. This is a web site for the wood industry. They have a knowledge base that includes designs for many kilns. It is not to difficult to build a solar kiln. The trick is in figureing out the drying schedules for the different kinds and thicknesses of wood. They also have information there on this. Gene Wengert is the resident forestry professor on that site and he will probably answer any questions you have.

[Frank Chaffee]

Rob,
Ken can in no way be construed as an insecure moderator while following thru with his voluntarily assumed responsibilities of maintaining the SMC TOS.

We Creek members may not understand all the reasoning behind the elucidation of the TOS, but they are clearly stated, and we agreed to abide by them when we signed up here.

To the best of my knowledge, we can spell out links to information by writing “such and such dot com”, but some direct links are expressly forbidden.

Frank

[Brett Baldwin]

A quick web search with "forestry forum" yielded an obvious site.