Simplest kiln - further reducing air-dried wood's moisture

[Chris152]

I've never used a kiln but have been reading around methods used. Until now, I've brought air-dried boards into the house (with central heating) and allowed them to reduce moisture content from about 20-18% to 10% before using.

I'm thinking to bring a 6' x 2' milled air-dried log home and trying to reduce its MC down to 10% in a shed before bringing individual boards into the house to work on. At some point, I'd also like to try a few large slabs for tables.
From what I can see, kilning usually starts a fair way above an air-dried state, after free water has left the wood (so the wood's maybe at about 30% MC?). So there's a fair bit more work to do in the kiln before it reaches typical air-dried MC, and therefore most kilns have far more work to do to get down to 10% MC than they would if just drying wood that's already air-dried).

If that's correct, can anyone point me to a really simple DIY kiln design that'll only have to reduce from about 20 to 10% MC? If I had more space, I'd just bring the whole log into the house, which would be the simplest solution.

Hope this makes sense.
C

 

[Woodbloke]

I remember seeing Rick Taylor’s set up in New Zealand a couple of years ago. He’s a turner and only uses ancient Kauri (pronounced ‘kohri’) for his bowls. He simply rough cut the blanks (he had three shipping containers full of the stuff) and sticked them in a sealed, airtight container into which was simple de-humidifier draining to the outside. He reckoned it didn’t take too long to dry out the blanks and it seemed a pretty simple method to me - Rob

https://www.thewoodturnersstudio.co.nz/page/421314

 

[Malc2098]

I've been watching Andy from Manor Wood for a while now. A recent fire has destroyed his barn an workshop, but this video is of his kiln build. He even made plans, costs etc available .

[youtubessl]DUrG4vHGG8Y[/youtubessl]

https://youtu.be/DUrG4vHGG8Y

Admin, I've no idea why the video doesn't come up when I preview, so I've included its URL. I'm on a Mac Mini.

 

[droogs]

have a look for solar kilns. They are pretty simple. only complex parts are making sure the angle of the perspex panels are at the same as your latitude and having to wire in a couple of computer fans to extract moist air.

some info here
https://www.youtube.com/watch?v=cTsDhCrE56U

 

[Chris152]

Thanks chaps.
Rob - I couldn't find the kiln article on that site.
Droogs - I know there are at least some solar kilns operating in the UK, but I'm not sure about how effective it'd be here in Wales. Wisconsin seems fine tho, and the minimal draw on electricity is very attractive
Malc - that kiln's being used for just the process I'm thinking of (reducing air-dried wood down), and looks good. Even better, I sent the link to a friend who has the wood and he's interested in working to build and run one together. It's probably more complex than I'd planned but as a shared venture, it should be do-able (tho we need to check costs of materials, given the current state of things.)
Much appreciated, all.

 

[Malc2098]

Thanks chaps.

Malc - that kiln's being used for just the process I'm thinking of (reducing air-dried wood down), and looks good. Even better, I sent the link to a friend who has the wood and he's interested in working to build and run one together. It's probably more complex than I'd planned but as a shared venture, it should be do-able (tho we need to check costs of materials, given the current state of things.)
Much appreciated, all.

That should be one helluva WIP Thread. Looking forward to it. You could even take in kiln time from members with slabs!

 

[Woodbloke]

Thanks chaps.
Rob - I couldn't find the kiln article on that site.

Nope, you won’t Chris. I only know ‘cos I asked him when we stayed with him for a couple of days. Apparently he uses old chest freezers (or similar) and is able to bring large chunks of kauri down to a respectable MC in a couple of months. No heat involved and the climate on North Island where he’s based is fairly temperate, so no hot, tropical temperatures etc.

As the wood ‘breathes’ the de-humidifier just sucks out all the moisture from inside the sealed box, but he was at pains to point out that if there’s a leak and the box isn’t airtight, the system doesn’t work - Rob

 

[Mike G]

If you are looking to do it on a regular basis, then I reckon using a shipping container would be a good bet. It wouldn't be difficult to get it properly sealed, and lining it with insulation would also be possible if that was in your plans. A dehumidifier, plus a temperature and humidity sensor, and off you go. With the price of timber at the moment, and in particular, the quality on sale, I reckon more and more people will be looking at some sort of DIY solution, and maybe even at taking wood from green to seasoned themselves.

 

[Chris152]

Rob - that explains it!

Malc - the link to the plans doesn't work, it's not available any more on his etsy site. But it doesn't look complex. The only immediate issue is the current cost of materials - wow, they've certainly gone up. As for a WIP, I don't think we could do better than the WM video, it's really helpful.

I'll look into the container idea Mike - I know my friend's thought about it before and he'd be looking to do it on a bigger scale and more regularly. From my perspective tho, it'd be far bigger than what I had in mind, and certainly little room for error with a container load of timber. Now I've got him interested, we're going to meet up early next week and talk it over.

Thanks for the thoughts, I'll let you know how it pans out.

 

[Cabinetman]

I know it’s not exactly the same but the principle is, I have a cupboard with two doors on the front it is 6 feet high 8 feet long and 2 feet deep, I use it to dry firewood, there is a fan in it and a dehumidifier of the desiccant type, this gives off a little heat and the temp often gets to ~ 35c. The "roof" is insulated.
It is extremely effective, no real effort to seal it except the doors fit reasonably well. If you were to use it for drying timber you would have to keep a very close eye on it and as Mike says you would need a temperature and humidity sensor connected to the power supply – I know from repeated experience my set up can reduce the MC so quickly that the wood splits and cracks, not really your intended outcome!
Please let us know how you get on. Ian
Edit, if the timber is a bit on the thick side I sometimes turn it off and leave it so that the moisture in the centre can Wick out to the ends – part of the keeping an eye on it business.