Small Bowl Kiln

[Bill Bulloch]

I build this small kiln to dry bowls in. I didn't have any green bowls turned at the time, so I loaded it with 13 board feet of boards I had cut to use in Segmented pieces (Walnut, Bartlett Pear, & Magnolia). All these had been cut about a month or so earlier and had a moisture content of around 20 percent when put in the kiln. It really worked. Two weeks later, the moisture content was less that 7 percent with absolutely no checking.

I ran the fan only for two days. I, then set the thermostate to 70 degrees for five days. I, then moved it up to 80 degrees for about five days and then to 90 degrees for two days.

I found a "How to" on another site: http://www.woodturningonline.com/assets/turning_articles/Kiln/Introduction.html
and build my kiln according to his instructions with a few modifications.

Mine is a little smaller than his, because I made mine from materials I had on hand. Mine messures 24" Wide, 21 inches Deep and 46 inches high. My sister and her husband own a Shipping and Warehouse business and I get a lot of discarded creats from them. I used one of these creats and sandwiched some R4 insulation board I had between some plywood from another creat.

I also, made my window, out of plexaglass I had, to open, so I could change the thermostate setting without disturbing the atmosphere inside. I used twist down latches which draw the door tight against the insulated door frame and you can see the hold down clamps I used to hold the window tight against the insulated frame. It took about 10 minutes to heat the box from 40 to 70 degrees with the two 100 watts bulbs I used. And, the box maintained the temperture very well. Over the course of the two weeks I checked the kiln everytime I passed by and never caught the lights on.


The only thing I had to buy were Computer Fans and the Thermostate, about $70 with shipping.


I can't wait to get it loaded with green bowls.

[Baxter Smith]

Looks great Bill! I will be very interested to see how it does with your bowls. Looks like something you could almost do with an old refrigerator. We just got a new one and sent the old one off!:(

[Michael Jasani]

An old refrigerator would probably require a few light bulbs and some ventilation holes for it to make it work in a warm place like L.A.

Bill, sure am waiting to hear from you when you try bowls

Thanks for sharing the idea and the pics.

[Bill Bulloch]

Looks great Bill! I will be very interested to see how it does with your bowls. Looks like something you could almost do with an old refrigerator. We just got a new one and sent the old one off!:(


I have seen plans on the web for making one out of an old refrigerator. They drilled 8 holes in the bottom and 8 holes in the top; used a 40 watt light bulb for heat -- no fan. The hot air rises drawing air in from the bottom, circulating it around the wood before exhausting it from the top. I thought about making one like that, but didn't have an old refrig. It would be bigger than mine. I don't know how it would work, but if it didn't you could always plug the holes and add a fan or two.

[Robert McGowen]

It looks like you will be turning some dry wood soon. One question though, where does the moisture go? It does not appear that there is any place for it to escape to. I am sure I am over-looking something.

[Bill Bulloch]

It looks like you will be turning some dry wood soon. One question though, where does the moisture go? It does not appear that there is any place for it to escape to. I am sure I am over-looking something.

You can't see in the pictures, but at the top, back of the fans are four ventilation holes. I have them plugged with wine corks, this way I can open them as needed. I have a humidistat on order that will be used to determine when the vents need to be opened. This, of course, will be a manual operation. I don't know how this will play out, but figure that when the humidity get close to 100 I'll open the vents and see what happens. The guy I copied this one from had vent holes in the top, but didn't mention any at the bottom. I figure that I will probably need to drill some in the bottom to let outside air in during the ventilation process. I don't have any instructions, so I'll just have to play this by ear and see what happens.

I didn't open the vents at all while drying these boards and it worked out okay.

[Sean Hughto]

What is it the kiln is doing that prevents checking? I have no experience with kilns, so forgive me if that is an ignorant question.

[Bill Bulloch]

What is it the kiln is doing that prevents checking? I have no experience with kilns, so forgive me if that is an ignorant question.

Sean, I'm not exactly sure. But, what I understand is that the checking and warping is caused by the mositure leaving the wood to fast. The kiln provides a controlled atmosphere that allows the wood to dry out at a slow, even pace. Some of the wood that I dried in the kiln had had the ends waxed, some didn't, niether checked or warped. When I get some bowls turned I plan on waxing some and not waxing some to see what happens. I suspect there will be some checking and warping in any event.

[Bernie Weishapl]

Bill please keep us posted as I have been thinking about a small frig. I would be very interested in how it works with the green bowls.

[Steve Schlumpf]

Looking forward to seeing your results drying bowls!

[Bill Bulloch]

Bill please keep us posted as I have been thinking about a small frig. I would be very interested in how it works with the green bowls.

I have 11 different trees cut and stacked in a shaddy part of my land. The problem is that it has rained so much over the past 3 months that it is to wet to get my truck down there to get any. And, we are expecting rain again this weekend too, but as soon as I can get a log or two I'll roughout some and give them a test run in the kiln. I'll post the results -- good or bad.

[Craig Schmidt]

Hi Bill, on your design do you have any vent holes in the bottom of your kiln to allow air to be drawn in as the fans force air out?

thanks, Craig

[Wes Ramsey]

For anyone planning to build a kiln like this, check your local auction house for old refrigerators or freezers. The one here always has a good supply that won't sell because they're too ugly or don't work and my buddy that works there has offered me all I care to haul off. I haven't picked one up yet since I don't have time to turn a lot, but thought I'd share a potential source.

[Lee Watermann]

Check Craig list under "free stuff" and you will generally find a "curb alert" for stuff like that.

[Ron Rutter]

Bill. I have the same question as others. How can you dry the wood if the moisture can't get away? The operation of a commercial kiln is fairly complicated and usually involves the injection of steam. Your success is probably related to the speed ( slow ) of your process. Ron.

[Bob Bergstrom]

We gutted an upright freezer at our Woodturning workshop a couple years ago. It is just drilled top and bottom with a light shocket and cord attached. We fill it with bowls, start wi a 40 watt bulb and go to 60,75 and 100 watt bulbs over a month to 6 week period.temps on 100 watt can reach 110 degrees. Smaller the bowl quicker the drying. We find if they cracked in the kiln, they probably would have air drying anyway. After a few cyles, we have a surplus of blanks. Enjoy the process and the free dry wood. The freezers are best because they offer one large opening with only one door.

[Scott Brandstetter]

Thanks for the thread and I too, will be watching and hoping for good results. I tried a version of this but gave up. I actually have the structure built similar to yours so I'm ready for the finer points. Have a great day and we all wish you great success.....so we can feed off of it.

[Bill Bulloch]

Hi Bill, on your design do you have any vent holes in the bottom of your kiln to allow air to be drawn in as the fans force air out?

thanks, Craig

Yes, I have four vent holes in the bottom and four in the top (sides). I plug them with wine corks and let the air circulate for a few days. When the Humidity starts to rise I open them, one at a time to allow the moisture to escape slowly. You know this thread was started five years ago. How time flies. I can't remember ever changing one of the light bulbs in the box.