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My kiln build

John Turpin

John Turpin

Joined
Jun 13, 2017
Messages
135
Likes
152
Location
OKC, OK
A few months ago, I began work on a dedicated bowl turning studio in my backyard. I've been thinking about this project for a year, but broke ground on it just recently. The building is 11' X 14' and is attached to my existing (tiny) 12' X 18' workshop. Planning for this build has been great fun. (Planning for the costs has been quite depressing.)

One of my requirements for this building is a bowl blank kiln--well, more of a drying closet--but to impress people I'm calling it a kiln. I'll post a photo now and then to show the process and the decisions I've made. When doing my research, I learned quickly that these things are sort of a lightning rod for turners. Depending on the turner, they are loved, mocked, valuable, dangerous, vital, worthless and certainly not as good as a paper bag. But, I decided to build one anyway.

The little closet is about 24" X 38" X 7' (inside dimensions). I'll get to the more glamorous insulation and heating technology later, but I'll start with the drip pan. Guys like Glenn Lucas have a steady stream of water running out of their kilns. I'll never dry that many blanks, but I decided to plan for a wet environment anyway. This weekend, I made sort of a removable 'drip pan' that will sit in the bottom. It is sloped toward one corner and a tube will be there to route water out the wall. Unless I put a bottle outside to collect drips, it might be a good spot for visiting raccoons to get a sip of woody water. The pan has been sealed with a coat of marine epoxy.

kiln1.jpg kiln2.jpg kiln3.jpg kiln4.jpg
 
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I think that you should consider putting Formica laminate on the walls, ceiling, and maybe floor because it will be humid and it will be easier to clean up and keep mold from becoming a part of the kiln if porous surfaces like wood and insulation are exposed to that environment.

Maybe also put in a bench so that it could be used as a sauna when not being used as a kiln. :D
 
Tom Albrecht said:
I like this--- I am curious about what you will use for walls and heat??
I am also curious about the size--- why not bigger?
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Hi Tom. As for size, I'm pretty squeezed for space already. Hmmm. Maybe I need a second story. [thinking] As for those details, watch this space.

Bill Boehme said:
I think that you should consider putting Formica laminate on the walls, ceiling, and maybe floor because it will be humid and it will be easier to clean up and keep mold from becoming a part of the kiln if porous surfaces like wood and insulation are exposed to that environment.
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I hadn't thought about mold. That would be pretty crummy. I think I'm going to start with foil clad insulation panels first. But, I'll make them removable so I can pull them off after a while and check on that mold business. Hopefully the circulating fan and ventilation will keep that at bay. If not, I'll line it with something slick and plastic.

Bill Boehme said:
Maybe also put in a bench so that it could be used as a sauna when not being used as a kiln. :D
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I like Idea Men. Why stop there? Why not just smoke briskets in there too?
 
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John Turpin said:
A few months ago, I began work on a dedicated bowl turning studio in my backyard. I've been thinking about this project for a year, but broke ground on it just recently. The building is 11' X 14' and is attached to my existing (tiny) 12' X 18' workshop. Planning for this build has been great fun. (Planning for the costs has been quite depressing.)

One of my requirements for this building is a bowl blank kiln--well, more of a drying closet--but to impress people I'm calling it a kiln. I'll post a photo now and then to show the process and the decisions I've made. When doing my research, I learned quickly that these things are sort of a lightning rod for turners. Depending on the turner, they are loved, mocked, valuable, dangerous, vital, worthless and certainly not as good as a paper bag. But, I decided to build one anyway.

The little closet is about 24" X 38" X 7' (inside dimensions). I'll get to the more glamorous insulation and heating technology later, but I'll start with the drip pan. Guys like Glenn Lucas have a steady stream of water running out of their kilns. I'll never dry that many blanks, but I decided to plan for a wet environment anyway. This weekend, I made sort of a removable 'drip pan' that will sit in the bottom. It is sloped toward one corner and a tube will be there to route water out the wall. Unless I put a bottle outside to collect drips, it might be a good spot for visiting raccoons to get a sip of woody water. The pan has been sealed with a coat of marine epoxy.

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I think you are spending more that me. I found a broken, about the same size as yours, glass door refrigerator. Cindy Drozda gave some input, and I have a great kiln. I dont have to open it to see how things are going, or to see the hydrometer. I finally settled on a heavy duty 15 watts bulb, used for ovens... How fun to plan a new shop! Aloha
 
I have a friend that just picks up broken dish washers. Drills some holes in them and then uses different size light bulbs to regulate the heat. He had 3 last time I visited and they are all in various stages of drying. this allows him to turn bowls over pretty quickly. I've also seen it done with old refrigerators. I've been thinking about just using junk cars. That way my yard would look more like my neighbors. :)
 
Emiliano Achaval said:
I dont have to open it to see how things are going, or to see the hydrometer.
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Hi Emiliano......:D

How does that work? Do you use a hydrometer to determine the MC of your roughed bowls? I'm so dumb about kilns, that I had to look it up:
hydrometer

[hahy-drom-i-ter]

noun
1.
an instrument for determining the specific gravity of a liquid, commonly consisting of a graduated tube weighted to float upright in the liquid whose specific gravity is being measured.
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-----odie-----
 
A hydrometer is what we use to check sugar content when boiling down the maple sap to make syrup.

You'll want to use a plain old Moisture Meter for checking wood moisture content.
 
I'm sure that he meant hygrometer ... an instrument to measure humidity. Just a spelling error, but context should clue the reader as to what was meant. The humidity of a kiln needs to be carefully regulated.

BTW, I used a hydrometer back in my vintner days to check the sugar level of the grapes.
 
Bill Boehme said:
I'm sure that he meant hygrometer ... an instrument to measure humidity. Just a spelling error, but context should clue the reader as to what was meant. The humidity of a kiln needs to be carefully regulated.

BTW, I used a hydrometer back in my vintner days to check the sugar level of the grapes.
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Well, speaking for my own ignorance, I did not know what a hygrometer was until now-- so in this case the "context" left me clueless.
 
Bill Boehme said:
I'm sure that he meant hygrometer ... an instrument to measure humidity. Just a spelling error, but context should clue the reader as to what was meant. The humidity of a kiln needs to be carefully regulated.

BTW, I used a hydrometer back in my vintner days to check the sugar level of the grapes.
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Thanks Bill for the correction, sorry for the confusion, lol. Its a little thing I got from Amazon, tells you the humidity and temperature. Its a guessing game at first, depending on the size of the holes, and size of the light bulb. I finally got success with 2 holes on the bottom, 1 1/4 each, and 2 on the top. And the oven light bulb, the lowest one they had.In 3 weeks I have the blanks for the boxes down to 10 %, so, super dry for Maui, then goes back up to 12.4 once out of the kiln.. Unlike Kelly Dunn, I do not place my Koa bowls in there, they go down to the gallery with 12.4 MC.... Aloha
 
I spent most of the day in closets. My new studio will have a "noise" closet that will house my noisy dust collection system and air compressor. And, of course, there's the kiln closet that's the subject of this thread. After a pre-sunrise run to the big box store for sheet rock and insulation panels, I started insulating. I envisioned this taking an hour or so. It took more like eight hours. But, the kiln now has 3 1/2" of pink stuff and another 1/2" of foil-backed rigid foam. Next, I'll be tackling the shelves.
20171104_144221.jpg 20171104_152715.jpg
 
Don't forget that you will need a thermostat to regulate the temperature. Otherwise, it will become an oven. A small fan to keep the air moving would be a good thing to have. Whatever you use for a door needs to have a tight seal.
 
Bill Boehme said:
Don't forget that you will need a thermostat to regulate the temperature. Otherwise, it will become an oven. A small fan to keep the air moving would be a good thing to have.
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Great points, Bill. I'm using the same stuff (mostly) that Sam Angelo did in his kiln build. I don't have working electricity yet, but have the thermo and monitoring devices sitting there waiting to go in. But first, I need shelves. I was going to use that plastic/wood material that they make decks out of. But instead, I think I'll just put in movable/removable cedar slats. Cedar should do pretty well in that environment.
 
After a week on the road (movin' and shakin', dialin' and dealin'), I got back into the studio-in-process this wekend and made some progress. The walls are now sheetrocked, mudded and textured. I'll paint later today.

While waiting for the mud to dry, I managed to knock out my kiln shelving. I've now got a set of adjustable cedar slats in five levels. I can rearrange them as needed for blank sizes. I could even put long boards in there (< 6'), but they'd have to stand on end.

slats sm.jpg slats 2 sm.jpg
 
Tom Albrecht said:
Still waiting to here what the heat source is--- or did I miss it?
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Hi Tom. The electric wizardry goes in this week. The current plan for heat will be a pair of light bulbs. If they don't produce enough warmth for that space, I may move up to one of those ceramic terrarium heaters or a heat lamp. But, hopefully a pair of incandescent bulbs will do it. And, that heat will be supported by a thermostat and a remote temp/humidity sensor. Photos to follow.
 
It takes a while for the temperature to reach steady state, but if your closet is well sealed then I suspect that you may eventually back down to just one bulb of perhaps 40 watts or so. My shop is so well insulated and sealed that in the winter the fluorescent lights (16 X 32 watts = 512 watts) and computer (500 watts) generate enough heat to keep it warm except on really cold days.
 
I agree that you are going to have mold issues there. Water vapor is going to get around the cracks of the foil insulation unless you caulk and tape it. If it gets in the cracks, the moisture will condense on the back side of the wall board. Mold loves the paper on that stuff!
 
Bill Boehme said:
It takes a while for the temperature to reach steady state, but if your closet is well sealed then I suspect that you may eventually back down to just one bulb of perhaps 40 watts or so. My shop is so well insulated and sealed that in the winter the fluorescent lights (16 X 32 watts = 512 watts) and computer (500 watts) generate enough heat to keep it warm except on really cold days.
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Yeah, but that's a Texas winter. ;)
 
Yea I think some people use fans to circulate the air to keep mold down but that's on larger kilns for drying flat wood.
 
Okay. I've finally made some progress on my bowl kiln. The new studio is almost complete now and all that's left is small projects. So, I climbed back into the kiln/drying closet this week. The heating element went in. It's a pair of incandescent bulbs that are controlled by a thermostat. There's also a small USB fan that will keep air circulating while pulling a very small power load. There's a 3" air intake in the bottom and another 3" vent in the top with a sliding lid. The weather station in the photo shows temp and humidity for both the studio and the kiln. I still need to install some weather stripping around the bi-fold door.

It's not time-tested, but some early test are encouraging. Some short heating runs show the space slowly heating, but I've not yet figured out how warm it will get in there. (I'd love to reach 90 degrees if possible, but that cold winter cement floor will prevent that now.) I can play around with bulb wattage as needed. I don't really have a dehumidifier for it and don't have plans to add one. Hopefully the circulating air will help get some of that moisture out. I might also put a tub of marine desiccant in there and see what that does. It will be interesting to play with.

kiln1.jpg kiln2.jpg kiln3.jpg
 
Wow, that is a nice kiln John. That should work great for your bowls and should help them dry much faster than my method of air drying in a bag of saw dust. Very nice indeed!
 
I read that if your cell phone/iPad/Andriod gets wet, you can bury it in rice. Wonder it that would work with wet wood???? After you turn the piece, you could make stir fry or rice pudding.
 
John Torchick said:
I read that if your cell phone/iPad/Andriod gets wet, you can bury it in rice. Wonder it that would work with wet wood???? After you turn the piece, you could make stir fry or rice pudding.
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Don't forget to remove the turning before serving the pudding. :D
 
John Turpin said:
That would be great. I'm curious to see if there is much of a difference in heating that space when it's full vs. partially full. It will be interesting to track.
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John, you will find that when you put in a fresh load, most of the energy is absorbed in vaporizing the water in the wood. As it dries the temperature will rise. I start with a temperature at or just above ambient and slowly get up to about to 95-100F. I have some charts I have done of temperature vs weight loss and humidity for a presentation I did for a couple of clubs. Will try to remember to look for it tomorrow on my computer.
 
This is great data, Mike. Thanks. I'm amazed that the humidity would change that quickly. I'd expect it to take weeks for what you got in 10 days. That's encouraging.
 
John Turpin said:
This is great data, Mike. Thanks. I'm amazed that the humidity would change that quickly. I'd expect it to take weeks for what you got in 10 days. That's encouraging.
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It appears that the chart is is showing humidity of the air in the kiln which isn't moisture in the wood. Initially the wood contains a huge amount of free water. Free water leaves the wood very quickly, but the bound water can't leave until the free water in the same ΔV has evaporated. Also, I think that Mike is saying that he has ten data points over about three weeks and the numbers don't mean ten days and the sampling points weren't equally spaced.
 
Bill Boehme said:
he has ten data points over about three weeks and the numbers don't mean ten days and the sampling points weren't equally spaced.
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Okay, great. That makes sense. I think I'll make a similar study to see what I find. I think my biggest problem is going to be heating that space. I've got about 70 ft3 and I'm not convinced that two bulbs can heat that adequately. I've got more options for heat, but am hoping that I can get up to temp without too much sophistication.
 
John Turpin said:
Okay, great. That makes sense. I think I'll make a similar study to see what I find. I think my biggest problem is going to be heating that space. I've got about 70 ft3 and I'm not convinced that two bulbs can heat that adequately. I've got more options for heat, but am hoping that I can get up to temp without too much sophistication.
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I built a film drying cabinet using parts from a ceramic heater that worked quite well. I put it on a appropriate capacity dimmer control to be able to fine tune the heat level as well as keep the current draw down. It didnt have the thermostat hooked up because it has a pass through air path to get the moisture out quickly so I wanted a low continuous heat. Since you are regulating how fast the moisture escapes you will be using a thermostat with a controllable venting system. These heaters have dual elements for low/high ranges it can be set on low power to limit current draw and keep the temperature from fluctuating so much.
 
John Turpin said:
Okay, great. That makes sense. I think I'll make a similar study to see what I find. I think my biggest problem is going to be heating that space. I've got about 70 ft3 and I'm not convinced that two bulbs can heat that adequately. I've got more options for heat, but am hoping that I can get up to temp without too much sophistication.
Click to expand...

John,

In my winter warfare training (Army), we were trained that a single candle would heat an igloo pretty well. I'd bet two incandescent lamps will heat this pretty quickly.

Kind regards,
Rich
 
Best thing to do John is to record and chart your various parameters on your first few loads. The humidity builds very quickly. You get to know what the percent loss by weight will be. An inexpensive digital kitchen scale that measure in grams makes it easy. Starfrit have a good one that is less than $20. I write the weight and date on a few pieces in the load to monitor. My kiln is about 15-16 cu ft and the air inlet and outlet is only three 1/2" holes. Depending on the wood it sometimes is totally wet inside. I found I baby sat the first few loads and after that put it in and checked it once a week or so for the duration. You may want to make up some things to reduce the interior volume for smaller loads as the high humidity in early stages is important. Not sure if they are still available but something like styrofoam coolers with their lids on would work.
 
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