To kiln or not to kiln?

[lazyguy]

Hi, All.

Long time lurker.

I've been thinking about buying a small mill for several years.
And I'm done waiting.

And I'm planning on purchasing 1 in the next week or so.
BUT.

There seems to be a ton of sawmills in use and being talked about, and almost nothing said, about kilns.

My question is:

For you're own use.

Do you own a kiln to dry you're lumber, or just air dry it?

I'm primarily interested in hardwoods, "oak, maple,walnut", mostly, for cabinets, cutting boards-gifts, ect.


I have been planning on just air drying my lumber and then bringing it into my house to acclimitize it.

But, if I have to be worring about kiln drying it also. Maybe I'm waisting my time getting a sawmill,
when I should just keep, buying kiln dry lumber.

Just looking for honest opinions.

Thank's
Dave S.

 

[Jim Timber]

Put a tarp over them if you're storing it outside.

Solar kilns are often nothing more than a "hot box" with ways for air to move through. The solar radiation raises the internal air temp (like how your attic gets hot) during the day and then cools off again at night. The thermal cycling is beneficial as it stress relieves the wood as it dries, and you don't end up with problems from differential shrinkage due to fast drying.

I'm sure someone with more knowledge will chime in, but I'm also in the early stages of getting a mill running, so I've been reading up too.

 

[Burlhunter13]

I use both methods. Lumber that is freshly milled gets air dried outside (under corrugated roofing panels or tarps, lifted off the ground 8"-1ft) for up to 6 months. Then, sometimes I'll throw it into the kiln to speed it up/kill bugs.

Most of my lumber is air dried though, keeps the cost down. Recently, when it hits under 20% I move it to my indoor stack. Equilibrium moisture content in my area for kiln/air dried lumber almost always stabilizes at 9-12%. I have an electric kiln and it will easily dry lumber to 6-7%, but once its taken out of the kiln the moisture content rises back up to 9-12% in about a month or 2. Unless we are in dry summer/winter months.

I'm still kicking around the idea of building a solar kiln....I've heard good things.

 

[Jim Timber]

I've thought about a simple boiler and heat exchanger inside a shipping container. You could fuel it with the waste wood.

 

[Burlhunter13]

I've thought about a simple boiler and heat exchanger inside a shipping container. You could fuel it with the waste wood.

.........I just had one of those "wow" moments.........good idea, I always seem to have too much waste wood/yard debris.

 

[Jim Timber]

I'd do a 20' with a carriage/cart that runs on rails inside it - looking something like a rail car with bunks on either side. Heat exchanger on the floor with no fear of damage due to the cart being on rails. Pull the whole load in and out in one shot. Load from the sides.

I'd also have it inside my pole barn, so the loss heat would heat my work space.

Some day I'll even have enough money to make it happen.

 

[Burlhunter13]

ohhhhhhh mannnnnnnn........this just keeps getting better! I'm going to seriously kick this around a bit......I dont know if I have enough space for a shipping container in the shop......maybe a small one. Dang, gotta get the creative juices flowin now. I have a large kiln at my fathers place (18'x6'x5' I think). Recently moved about an hour from his shop, so Im supposed to bring the kiln with me, he doesnt want it sitting unused. I kept debating on making a smaller one for inside my shop......hmmmm. Thanks for the ideas!

 

[Jim Timber]

How did you handle the kiln at your dad's place?

I figure, if I'm going to be making lumber, I might as well use as much of the tree as possible. I'll have to go outside my business model to deal with firewood (and transport it to a market where there's any money in it), so why not use all the scrap I can to lower my operating costs?

Shipping containers run about $2500 here, so I could build a room cheaper but not by much for the same air tightness and critter proofness.

I'd exhaust the kiln outside the shop to keep internal humidity down, and also take external make up air as well so as to not suck all the heat from inside the building. In the summer just open the doors to keep it reasonable.

 

[Burlhunter13]

The kiln at my dads place was a little big (if I were to make another one). I could easily fill the thing in a good weekend of milling, but I normally milled on and off in-between my regular work scheduled. So I would make a stack of lumber to air dry outside untill I had enough to make a good load in the kiln, trying to make it as cost effective as I could. Which ment I had to stack the lumber twice. When we first built the kiln I was stacking the lumber directly into it and once it got full (maybe 3 weeks some months) then I would fire it up......problem was leaving the freshly cut limber sit in a box with not much airflow. I was having mold problems.

So, I would make the next one smaller so I could fire up smaller loads as they piled up......and if I had overflow then I would let it sit to air dry untill the kiln load was done. Usually 3 weeks to a month for beautiful dry hardwood.

Im gonna do some drawings of my shop/yard possibilities for a smaller kiln next spring.

 

[Dad2FourWI]

@ Burlhunter13,

Great comments... please share your thoughts and plans as you progress and as you make your kiln, take lots of pics for us here so we can drool over your work!!!!!

-Dad2FourWI

 

[STLfirewood]

How did you handle the kiln at your dad's place?

I figure, if I'm going to be making lumber, I might as well use as much of the tree as possible. I'll have to go outside my business model to deal with firewood (and transport it to a market where there's any money in it), so why not use all the scrap I can to lower my operating costs?

Shipping containers run about $2500 here, so I could build a room cheaper but not by much for the same air tightness and critter proofness.

I'd exhaust the kiln outside the shop to keep internal humidity down, and also take external make up air as well so as to not suck all the heat from inside the building. In the summer just open the doors to keep it reasonable.

I have a firewood kiln that works the same way. First you will need an insulated container. Stainless Steel works the best. When you are drying oak it will really corrode things. My kiln has a humidity gauge in it. When the wood sweats a certain amount the side vent open up and exhaust the moisture out. It works very well. It has 2 fans that move the air all the time. My 20ft container has a 235k btu exchanger in it. I run it at 195 degrees. I have thought about drying lumber in it but I haven't had the chance. It usually has firewood in it.

Scott

 

[Burlhunter13]

I have a firewood kiln that works the same way. First you will need an insulated container. Stainless Steel works the best. When you are drying oak it will really corrode things. My kiln has a humidity gauge in it. When the wood sweats a certain amount the side vent open up and exhaust the moisture out. It works very well. It has 2 fans that move the air all the time. My 20ft container has a 235k btu exchanger in it. I run it at 195 degrees. I have thought about drying lumber in it but I haven't had the chance. It usually has firewood in it.


You should start a new thread or post some pics of the kiln you got there!!!! I have noticed the same thing with oak on my bandmill and tablesaw. The oak will almost instantly rust any clean iron it touches when its freshly cut. It also stains dark purples to blacks quickly. Very high in tannins!


Dad2FourWI: Thats why I come up here! I end up drooling at what everyone else posted! I gotta figure out what Im doing still, but If I decide to build a new one I will definitely post! I should start posting more pics of logs I cut up, but Im always forgetting the camera. Im supposed to go up to Juneau, WI today to do some milling, If he confirms with with me soon :bang:.

 

[Cody Colston]

If you are sawing lumber for your own use, a kiln is not a necessity. It will be slow in the beginning while waiting on the lumber to air dry and then waiting more for it to dry inside your shop until it is at an acceptable MC for furniture...8% MC.

Depending on the type, a kiln can do more than just speed up the drying process. Most importantly is that you have control over the drying rate. If air drying, you are pretty much at the vagaries of the weather. Too many days with no wind and the lumber can mold, mildew or stain. Too many days with a hot, dry wind and the lumber can dry too fast, rendering the entire stack nothing but firewood.

A heated kiln, whether solar or artificial heat, will set the pitch in sappy woods like Pine or Spruce. Heating the wood throughout to 132 degrees will also kill any bug infestation. In the South, that can sometimes be accomplished with a solar kiln but in northern climes, the heat is probably not high enough for long enough to get the wood to that 132 degree temp all the way to the core.

I have a solar kiln, sized for 350 bft with a single 1400 cfm fan on a 24 hour timer. it does a great job since I only mill for myself. I have enough stock accumulated that I'm in no hurry to dry new lumber, either. I put it in the kiln, just barely crack the vents and forget about it. The fan comes on at 10:00 a.m. afer the outdoor RH starts dropping and then it goes off at 8:00 p.m. The heat drops inside the kiln, the RH rises and the lumber is stress-relieved. I dry mostly Oak and Walnut, neither of which is stain-prone so I don't worry about too-slow drying. I just fill it and forget it until I have another load ready. Most of the time, the lumber that I take out of the kiln is at 6% MC.

 

[lazyguy]

Thank's for the replies.

I only use about 300 or so, board foot of hardwood a year.
And I've only used kiln dried lumber, I've had quit a few case hardened boards to say the least.

I had figure'd I'd just let the lumber air dry on my deck under cover for a few months to get most of the moisture out.
Then sticker in my garage. The door seals are old and it's an airy garage.

But, I'm worried about bugs. I have access to walnut, maple, red oak, ash.
I have 3 people offering me lumber, and I don't even have a mill yet.

I figure my lumber useage to go up if I can get cheaper lumber. I'm paying about $6 a b.f. for walnut and maple. It hurts my "cheapness" to hand over $600 bucks for a small load of maple!

After more searching on the web, I'm thinking about making a small knock-down d/h kiln.
That would dry about 200 b.f. of lumber. I could work around this for 2 or 3 weeks waiting for the lumber to dry.

Dave S.

 

[Dave Boyt]

You can get by with air dry lumber for a lot of things, even inside the house, if you design for shrinkage. Trestle tables held together with wedged tenons are a good example. That's why they were designed like that back before kiln dry wood was common. Bugs are a big deal, and a minimum of 140 deg F is a good idea. I had a round with powder post beetles a few years ago. Little piles of sawdust on the floor and holes in the beams. Wouldn't wish that on anyone. Nyle has a small kiln that you might take a look at. Household dehumidifiers just won't stand up to the corrosive environment. Use an insulated enclosure, for sure.