# building me a big boy bowl kiln



## bond3737 (Nov 13, 2009)

hey all thought I would process what I am thinking here and see if I'm on the right track. Ive done a bit of reading on kilns and kiln plans but have drawn up something that may or may not be to complex. (my head has a habit of overbuilding things.) Hopefully the following will make sense. 

1. Size- the kiln will be approximately 4X4X12 feet long. insulated from top to bottom. Am still looking for a thin yet effective insulation

2. Common household dehumidifier will be used 

3. Lights will bring kiln up to temps and dehumidifier will keep them there though I'm pretty sure they will be completely unnecessary during the summer as it's hot as hell in my shop in the summer 

4. hygrometer used to keep humidity and temps to spec

5. The best way to visualize what I would like to do is to picture a box that essentially has a wind tunnel in it that goes in a big oval loop. The entire box is as air tight as possible. The dehumidifier will be on one end sucking air in and removing water. The top and bottom of the dehumidifier will be sealed from the top of the kiln to the bottom. Picture a dehumidifier with ply wood surrounding it that has been sealed with tape or plastic or whatever creates the best seal. 

6. the air that goes through the dehumidifier and is spat out the back end while the water is vented out of the kiln.

7.The air that goes out the back is heated and goes into a rectangular chamber where the first set of window fans pics it up and sucks it through. This fan blows it down a narrow hallway (probably the width of the fan) that goes the length of the kiln. So picture the hallway as a separation between the bowl area and the back kiln wall. 

8 The dehumidified air travels down this hallway to the end of the kiln where it takes a left turn and meets another fan again sealed air tight which then blows the dehumidified air onto the bowls. The air travels over the length of the bowls and is propelled by the suction created by a third fan at the end of the bowl hallway (again sealed) which blows it into the chamber where the dehumidifier dries the air, releases the moisture and begins the process again by shooting the dry air into the back hallway fan.

I have a lot to learn on this subject before actual construction and again I may be overthinking this. My objective is to be able to dry as many bowls and small stock spindle size blanks as I can. The size of the kiln has been constructed to match my production rate of green bowls over a 1 month period in a cycle so I can spend half the month wet turning and half the month finish turning. 

SO with all that said feel free to chip away at, ask questions about suggest links to sources, give better advice on, etc etc etc. this idea. I am literally going off what makes sense in my brain. Hot dry air over bowls, bowls releasing moisture, moisture travels to dehumidifier. I havent seen any plans like this and perhaps there is a reason but figured i'd float it anyway. Thanks for reading happy turning, 
Bond


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## hwebb99 (Nov 27, 2012)

I thought the idea was to slow down the drying of green turnings.


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## bond3737 (Nov 13, 2009)

initially yes the goal is to slow the drying will put in a bucket of water to help with this process and the dh will not be turned on for the first 4 days to prevent TOO rapid of moisture loss


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## Bill Boehme (Feb 9, 2014)

The goal is to prevent cracking. That is normally accomplished by slowing down the rate of moisture loss. a drying chamber controls the rate of drying which otherwise is at the mercy of the environment where the bowls are stored. Typically, I have found that waxing the rough turned bowls with Anchorseal and then storing them in my air conditioned and heated shop works just fine. It sounds like you might have gotten some information from Trent Bosch. He designed a drying chamber with fans, heater, and dehumidifier. The time that it takes is about the same as I let things dry in my shop/garage. Trent lives in a very dry climate so he needs something to prevent the wood from drying too fast. I don't have that problem here. Unless you are a production turner, I don't see why you are going to all of this effort.


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## 9thousandfeet (Dec 28, 2014)

Honestly, a better strategy is to just let your rough turnings air dry naturally, and if you arrange your timing so that you always have some rough-turned work that's a year or more old, you'll always have dry pieces to finish turn any time you want.

The reason this is a better strategy is that it has no moving parts, costs neither time nor money to build (well, maybe some shelves to store things for a year or two), can't break down, and doesn't extend either your overhead or the amount of time it takes to make a piece, and therefore doesn't increase the price you have to charge for it.

The only downside to this plan is that for the first couple of years you won't have the inventory built up to make it happen, but once you do, you're home free and you don't ever have to fuss about how to speed up drying ever again.
And speeding up the drying process, even when it works without increasing the amount of loss due to checking, never, and I really mean _never_, improves the look and feel of the wood, and it usually degrades it. Wood becomes less agreeable to work and oftentimes grain clarity suffers, just for starters.

All in all, you can get a better system up and running with nothing but a bit of discipline to build up the initial inventory. No money required, no extra dedicated space required, no power consumption, no mechanisms to break down. 
No nothin'


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## bond3737 (Nov 13, 2009)

Ive been air drying my bowls for years and have had good success with this method. I've been turning table legs for a living for the past year or so as the bowl business gains speed. Ive gotten my bowl process as lickety split as I can for the moment especially trueing and finishing side and in the process of selling ive sold away the stock that is dry with little time to replenish between the table legs and finished bowls. A year and a half ago I was nowhere near as proficient in the roughing stage of things and so the issue arises of how to dry the bowls at a higher speed so that I can sell them quicker. Glenn lucas has a kiln that while on a much larger scale (think he uses a shipping container of some kind) is exactly what I'd like to accomplish. I think he said his bowls take in the neighborhood of 8 weeks to dry once they are in the kiln. I wouldn't go this route if these werent the ones that were selling but they go way faster than the ones that have been green turned warped and then sanded. While I find these bowls beautiful it does not seem to be what's sellin The hygrometer and thermostat should help me a great deal in regulating both humidity and heat within the kiln itself and there is no doubt that this is going to take a huge amount of tweeking I'm just looking for a good starting plan.


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## 9thousandfeet (Dec 28, 2014)

Yeah, it can be a problem if I spend so much time on finishing bowls that I don't turn enough green stock to replenish the supply line. So I don't do that. 
It's kinda like a farmer's Rule #1. Never, ever, eat the seed corn.

I gotta say, I don't see how speeding up the drying process could possibly shorten the time it takes to make a bowl. I don't see how it could increase my annual output.

It takes what it takes to harvest the wood, haul it home, then prep the blanks. It takes what it takes to rough-turn a bowl then paint the outside, or the entire bowl, with Anchorseal then toss it on a shelf someplace to dry. 

Then it takes what it takes to finish-turn it, sand it, and apply whatever finish you're using.

With unassisted air-drying, the time between rough-turning and finish turning is just elapsed time— not production time—which has no labor or energy input. So it adds nothing to the cost of the finished bowl.

Loading bowls in and out of a kiln takes labor. The kiln itself requires maintenance and attention which is more labor. And it needs almost constant energy input which mean cash money.
All of that _does _increase the production costs. 
It also chews up time which would be more profitably spent turning extra stock, so it's likely to decrease my annual output unless I work extra hours to make up for it.

So I hear ya, and maybe I'm missing something, but I don't see the benefit once _all_ the beans are counted. 
Something like this makes even less sense for a production turner, at least to my eye, than it does for a hobby turner who is just trying to pay for his tool habit and who has all the time in the world to build new widgets because they're sexy and fun.


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## hwebb99 (Nov 27, 2012)

You could rough out a lot of bowls in the time it takes to build the kiln. You will also waste a lot of time trying to get it working right. Then more lost stock due to cracking.


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## Bill Boehme (Feb 9, 2014)

Bond, I agree with what 9K' says. Your idea is to speed up drying, but whe3n yo have a full pipeline what does that matter? The reason that Trent Bosch (and possibly Glen Lucas as well) uses a drying chamber is not really to speed up drying ... it is to have a well controlled drying process in order to reduce the number of failures caused by splitting.

After you have rough turned a very wet bowl and set it out to dry, my experience is that almost all of the free water is gone in 30 days and this is if the roughed out bowl has very thick walls. At 60 days (8 weeks) roughly 2/3 of the bound water is gone and at 90 days (12 weeks) the turning is mostly dry. By 120 days, it should be, for all practical purposes, dry. For many types of wood, there is no need to wait until a piece of wood is bone dry before doing the final turning. There is not a great deal of moisture at 60 days (8 weeks) and you can generally finish turning at that point. The spinning will contribute significantly to removing the last remnants of moisture.

*Something very important to consider if you don't already know it* -- you will need to turn like a madman to fill the chamber with green rough turned bowls because you will need to get all of them into the chamber rather quickly or they will begin to split. *THEN*, once you fill it up, you close it and then *DO NOT* open it again until you have reached the end of the drying process. You do not get to incrementally add fresh green bowls into the chamber nor remove older dry ones ... *THEY ALL GO IN AT THE SAME TIME AND THEY ALL COME OUT AT THE SAME TIME*. The reason is that you will be operating the chamber with a progressive schedule of gradual humidity reduction. You can't do that if you are continually feeding fresh rough turnings into the chamber.


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## Bill Boehme (Feb 9, 2014)

Do not make this into a wind tunnel. You aren't designing an airplane, you're just drying wood. You want the fans to just very gently waft the air through the chamber -- a breeze that can barely be felt ... most definitely not gale force wind.

This box sounds really large. How many bowls are you planning on putting in it? With this setup it sounds like your production flow is going to be uneven: turn a bunch of green wood to fill the box ... open the box and remove dry stuff then load it up and start another drying cycle. Then you can crank out finished bowls for a few weeks before you must switch over to turning a bunch of green rough-outs. What a mess compared to taking dry rough-outs off the shelf and turning them and then turning some green wood to replenish your stock. Makes for a steady work flow.


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## bond3737 (Nov 13, 2009)

I appreciate the input thus far, I honestly do. But lets assume a few things- first is that I'm going to do it anyway. Second is that I don't have a year and a half to dry green bowls at this point. Third is that I am seeking ideas to help to build a kiln and not whether it is wise or not to do so. I'm not trying to be snotty, seriously, I really am not but I'm here to build a kiln. I understand that I should have been green turning the whole time as stock was going out but if you can sell something you're not going to sit on your hands and say no I'm saving the wood until I catch up with my green turning. Fourth, I am aware of all the ways to dry wood without using a kiln. Let's assume that this may be my best option right now. Lastly it is my fault for not saying all of this upfront not yours and that is on me I'm here for you're thoughts and input on these plans. I want to use this forum as a way to gain knowledge and have always loved the brotherhood found in completing projects, learning, and sharing info with the folks on this lovely site. We could all learn a ton by this whole thing and worst case scenario we can learn what not to do! haha. New doors can be opened new mistakes made new knowledge gained. From hence forth I dub this Bonds big wacky kiln build keep the creative juices flowin, happy turnin all,
Bond


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## bond3737 (Nov 13, 2009)

sorry posted before I read last three!


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## bond3737 (Nov 13, 2009)

swear to god ive got foot in mouth syndrome today... I blame the heat, intelligible post to follow.


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## hwebb99 (Nov 27, 2012)

If it is that hot there in the summer could you just build a box and line it with plastic? You shouldn't need insulation or a heat source other than the outside air.


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## Bill Boehme (Feb 9, 2014)

OK, I understand. I do things sometimes just because ...

I have offered some ideas and don't really have any more thoughts at this time. You might check with Trent Bosch to see if he is still kiln drying his wood. One thing that he mentioned is mildew and mold if the humidity is a bit too high. You probably need a window to peek in and see how things are going. Bowl turning really isn't my thing, but it seems like I still wind up turning a bunch anyway for things like Empty Bowls.


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## bond3737 (Nov 13, 2009)

"After you have rough turned a very wet bowl and set it out to dry, my experience is that almost all of the free water is gone in 30 days and this is if the roughed out bowl has very thick walls. At 60 days (8 weeks) roughly 2/3 of the bound water is gone and at 90 days (12 weeks) the turning is mostly dry. By 120 days, it should be, for all practical purposes, dry. For many types of wood, there is no need to wait until a piece of wood is bone dry before doing the final turning. There is not a great deal of moisture at 60 days (8 weeks) and you can generally finish turning at that point. The spinning will contribute significantly to removing the last remnants of moisture."
-This is very useful information, I had always gone by the year per inch rule regardless of type of wood etc and paid little attention to how much and how dry they were. 
- In terms of the size, yes it is going to be large and my thinking on it was that I would rather have something I can grow into than something that does not end up being large enough. 
- Yes turning all of the pieces at once is a huge task but Im totally up for it. When I process the log I'm getting two big bowls per side then I use the upper and lower for plates/ spindle blanks etc. I bandsaw em to round throw em on the lathe turn green then return. I turn or do something related to turnin for about 10 hours a day as is. Most of that is table legs but Ive been trying to move sales over to bowls because thats what I dig most. Ive hit a bit of a lull and want to up my game and figure this is the best way to do it. I can get about 25 bowls through the roughing process per day, chainsawed, bandsawed, and stacked and Ive got a metric ton that are still dated and drying. I will use the aforementioned math on the pieces I already have and see what shakes out the other end in terms of acceptable movement. Id either turned em wet and watched em get wonky or waited till bone dry to return em 
- In terms of the current conditions, my shop is un airconditioned and unheated. There are no windows and it's a garage so its hard to change the ambient temperature or humidity in the room. And it is HUMID. The goal as you stated to control the drying as best I can and find the easiest way to do that. With the chamber I have the advantage of removing some of that moisture from the muggy atmosphere that is my shop.
- Thank you for the advice on my jet wind tunnel idea. Scratch that one off the list, light breeze check. I like the idea of the kiln because my shop is almost as subject to the elements as if I just threw em outside. I wonder if my ladyll let me take over the basement
- The cycle is the thing that will need the most work to be sure. How many can I turn in a day how many can I finish turn in a day at full chap etc etc. My main question is this- If I can rough say 100 bowls in a week or thereabouts if I cover the roughed ones in plastic tubing while already anchor sealed is that ok? How long can they be left out of the kiln before the bowls I turned on day one are no longer ok to put in with the ones on day three. 
Will do some more thinkin and readin on this tomorrow. MUCH TO LEARN! Thanks all


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## 9thousandfeet (Dec 28, 2014)

bond3737 said:


> I understand that I should have been green turning the whole time as stock was going out but if you can sell something you're not going to sit on your hands and say no I'm saving the wood until I catch up with my green turning.


 This might make you mad, but no sir, you don't understand the issue with enough clarity yet otherwise you would not have unbalanced inventory. 

And no, I'm not going to "sit on my hands", I'm going to keep turning what needs to be turned to keep my product flow viable and profitable, and if there is a sudden surge in demand for finished work which I don't have finished inventory to satisfy, then I _*am*_ going to tell people that there's a rhythm to this kind of work which must be adhered to and they're just going to have to wait. Some will indeed wait, and if the work is honest and good and priced fairly they will be delighted to wait and may even value the piece all the more for having waited, and they will be wonderful references. 
Some just won't wait, and won't become customers, and that's fine too. 

And the reason I *must* do that is because there really _*is*_ a rhythm to it, and if that rhythm is interrupted efficiency goes to hell in a handcart and the whole production process comes unraveled and I'd find myself in exactly the situation you're in now, with unbalanced inventory.
That situation is not caused by the absence of a kiln, nor will it be resolved by building one.


bond3737 said:


> But lets assume a few things- first is that I'm going to do it anyway.


 Fair enough. 
That being the case, all I can think to add is be sure to read again what Bill said about how the kiln must be loaded then run until all the contents are as dry as you want them. _You can't keep adding stuff during the drying cycle._
And it's possible to stack a couple of hundred bowls in a lot smaller space than you might at first think, even allowing for gentle air circulation around them. So unless you're going to be working in batches of many hundreds of bowls, the whole drying unit will not need to be unduly large.

Happy Trails.


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## sawdustfactory (Jan 30, 2011)

Don't know if I'm way off base here but here it goes anyway. Probably smaller than what you want but I've seen a lot of people use old upright freezers as kilns for drying turnings. Already well insulated. Standard 40 watt bulb provides enough heat. Install a drain pan/hose at the bottom and use an old computer fan to circulate the air.


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## 9thousandfeet (Dec 28, 2014)

There's another issue to consider here too, and at this point I don't care if anyone gets mad or not.

Many well-known "production" turners like Mahoney and Lucas and no small number of others produce work which bears their name, but which they haven't in many cases ever even laid a hand on, even though it is a product of their "studio" and bears their signature.

They often have people working for them, journeymen turners, who produce lots and lots of pieces according to the studio's established patterns. They have other people whose job it is to gather and deliver and prepare the wood for the lathe. Sometimes they have a "finishing" room where other people apply the oil or whatever, then stack the pieces for drying. And so on.
Consequently they have a much higher volume "throughput" than is possible for someone working alone as a solitary production turner.

In such high-volume settings _everything_ must be sequenced reliably. So what's going on in situations like that, with the introduction of drying kilns, is not so much that the drying time is decreased (though it may well be) but rather is made predictable and (most importantly) repeatable so that the production process is not derailed by inclement weather or some other environmental variable.

Nevertheless, and this is the very center of this issue, the requirement for keeping every stage of production properly stocked with inventory remains _absolutely unchanged. 
_
For a solitary production turner, introducing a kiln into the production process cannot avoid chewing up the turner's time which would otherwise be available for turning, _and will therefore necessarily decrease, not increase, the overall output._ It will also necessarily increase production overhead while decreasing volume, and thus will decrease profits unless prices are raised to compensate. 
Put another way, if I introduce a kiln into my process, I'm taking a pay cut unless I jack up my prices to make up the difference.

It's a solution in search of a problem. It's counterproductive.


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## bond3737 (Nov 13, 2009)

thanks sdf I had thought about something similar to that but on a slightly larger scale. I think I saw carl jacobson build one similar. Bill Im gonna give trent bosch a jingle and see if he can give some good advice. Still playin around with the dimensions on this. In my free time I think ill start putting together a must have parts list for this and see where I can trim back some and move forward. I like the kiln idea because it's as hweb mentioned it's a seasonal thing I wanna control the climate as opposed to being subjected to it. In the summer itll help remove some of the humidity from the air and keep a nice airflow going over it and in the winter time it'll provide some heat and continue the drying process. Think Im gonna spend some time this week working on both dimensions and tweaking the necessities list keep the good ideas commin happy turnin, 
Bond


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## Bonanza35 (Jan 20, 2011)

9thousandfeet said:


> There's another issue to consider here too, and at this point I don't care if anyone gets mad or not... It's a solution in search of a problem. It's counterproductive.


I hope I'm not reading too much into your posts, but it almost seems like you're not 100% convinced that a kiln in an essential part of the production line. 

Somehow this became a kiln bashing thread when all he asked was for build tips. The man wants a kiln. Sounds like a fun project. I wish I had kiln knowledge to share but I've never messed with one. Keep us posted, Bond.


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## 9thousandfeet (Dec 28, 2014)

Bonanza35 said:


> I hope I'm not reading too much into your posts, but it almost seems like you're not 100% convinced that a kiln in an essential part of the production line.


 Heh heh.
Yeah, it now looks, even to me, like I came on a little strong.

But in my defense, Bond described the motivation for wanting a kiln as being; "..... so the issue arises of how to dry the bowls at a higher speed so that I can sell them quicker."

This led me to believe, mistakenly I now see, that Bond was exploring the_ idea_ of a kiln as a solution to the problem of unbalanced inventory and the need to "speed things up". 
So, off I galloped, trying to explain how it's not a solution at all but actually makes that very problem worse. Because it ain't, and which it will, assuming we're talking about a one-person operation.

But you're absolutely right. The man wants a kiln and that's that.

So sincere thanks for the reality check. I meant no harm.

And Bond, my apologies for being unnecessarily abrasive.


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## Bill Boehme (Feb 9, 2014)

I think that I may have been trying to save Bond from himself, but as John Wayne said in one of his movies, "A man's gotta' do what a man's gotta' do".

I wasn't intending to bash the kiln idea -- they do work, but I was judging his idea by my needs which aren't the same since I can't fathom the idea of selling stuff that I make.

Last year I took part in an exhibition with six other wood artists and even though I only had five pieces, it seems like I spent more than half a year getting all of my pieces ready. I guess that I'm the tortoise, not the hare.

I just finished a platter, working on and off, that I started almost a year ago -- the turning part was nothing, but the woodburning and coloring almost drove me crazy.

It's hard for me to imagine turning enough bowls to make a living. When Mike Mahoney was at our club last year he said that teaching is the only way to make a decent income -- that plus having a line of signature tools and other gadgets to sell.


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## Improv (Aug 13, 2008)

Another approach you may want to consider would be a closed (well-sealed) box with a single opening for a high CFM fan. So rather than blow air through the chamber, you are seeking to create a slight vacuum by blowing the air out of the chamber (faster than it can leak back in), i.e., a blocked up vacuum cleaner. Which if you want to test if it works before going through the process of building a large box, would be to plug up a shop vac with a test piece inside the container.

Regards,
Steve


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## Bill Boehme (Feb 9, 2014)

Bond, I forgot to mention Bruce Hoadley's book, Understanding Wood. I think that it will be very helpful in designing your kiln.


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