# Small wood drying kiln



## TomC (Oct 27, 2008)

Has anyone built a small wood drying kiln? I'm not talking about something like the dehumidification kiln. I am thinking of a a couple of cubic feet of space with a light bulb and a thermostat to control temp in the 100 to 110 degree range and of course a fan to move air. Not sure how big a vent to let out air and where to locate vent. I would like one to dry small pieces for turning. Again not talking about dehumidification kiln. If anyone has built one or seen one would you be willing to share plans or info.
Thanks,
Tom


----------



## Dave Paine (May 30, 2012)

I was at a turning show in March which had a person demonstrating turning a bowl.

The demonstrator used green wood and then explained his method for drying the blanks. He built a wood framed box, with rigid insulation panels and used a light bulb for the heating. I think he was only using 40W or 60W bulb. He did not have a thermostat for control. He relied on the bulb putting out consistent but low level heat.

I do not recall if he had a vent or a fan. If I were to include a vent, I think I would place this at the bottom.

If you want to use a fan, consider the small e.g., 4in fans used in PC's for cooling. Many are DC, but you should be able to find ones which run on AC. The DC ones can have variable speed. I have one sitting next to me for future use in a computer.


----------



## NCPaladin (Aug 7, 2010)

I have seen appliances (upright freezer, etc) used. They just drilled a small hole in the bottom and a small hole in the top and I think a 60 watt bulb near the bottom. Holes were 2” or less. Convection takes care of air movement you really don’t need a fan.
If for small items like pens or bottle stoppers a trashed microwave should work fine. I would drop the bulb down to at most 25 watt.
I’m sure you can rig up a thermostat but I would try it with just the bulb and place a thermometer in it and monitor until you got the correct heat over a day. Just add a damper to the intake at the bottom and adjust the heat that way.


----------



## doug1980 (Mar 28, 2011)

I made this one a few years ago. Still works well. Old Military insulated cooler. Drilled a few holes in the top, use a 100 watt bulb and small fan. Dries my bowls in a few days.


----------



## TomC (Oct 27, 2008)

Thanks for the info. If I can find a thermostat cheap enough I think I will still use one. I had not thought about using an insulated cooler. That would be cheap to experiment with. It will already have a holle at the bottom. I guess I will start with the 25 watt bulb and see how well it can maintain temp. Am I correct that I want the temp in the 100 to 110 degrees F range?
Tom


----------



## aerocustomsexotics (Jul 21, 2012)

I would be interested in seeing your finished product, I have thought of making one myself.

Bill


----------



## SeniorSitizen (May 2, 2012)

I use a microwave for smaller pieces but rather than putting a bulb inside I push start. A handle ferrule fit snug at near 0 moisture never loosens when the wood regains back to about 6 percent.


----------



## thisnobody (Mar 17, 2010)

Recently built one out of an old dishwasher myself.
Used a thermostat for a green house for controling the on/off function based on a given 10 degrees variance. Also put a dimmer switch for the light bulb (80 watt) so i can change the temp of the light to keep the unit from cycling on and off to frequently. I did put in a fan with another switch so I can manually turn it on or off. Dishwasher is good because of the vents already being in there and already insulated. If desired I can post some pics later.

TED


----------



## TomC (Oct 27, 2008)

thisnobody said:


> Recently built one out of an old dishwasher myself.
> Used a thermostat for a green house for controling the on/off function based on a given 10 degrees variance. Also put a dimmer switch for the light bulb (80 watt) so i can change the temp of the light to keep the unit from cycling on and off to frequently. I did put in a fan with another switch so I can manually turn it on or off. Dishwasher is good because of the vents already being in there and already insulated. If desired I can post some pics later.
> 
> TED


Ted, I would like to see a picture. I found a thermostat that has a 3 degree F band. Have you used yours yet? If so how long to dry and what temp are you controlling at? Thanks,
Tom


----------



## Firechic (Dec 14, 2012)

I built one with a small fridge simply wired in a light bulb socket and a 15w bulb will get it to above 80 deg f I didnt have a vent and typically only dry wood for turning that is already very low in moisture, I would dry wet wood slowly like in a plastic bag with its sawdust to reduce the checking, cheers FC


----------



## thisnobody (Mar 17, 2010)

CLICK ON THE LINK BELOW FOR EXPLANATIONS
http://s925.photobucket.com/albums/ad99/thisnobody/Dishwasher Bowl Kiln/

The explanations are in the descriptions of the photos.
I prefer this method to the bags of shavings, newspaper, anchorseal, boiling and all the other hoopla.
If you are planning to do a lot of turning then I would build something similar.
I also occasionally put a humidity gage in there to see what the RH is. It rides between 80% (freshly loaded ) down to 60% (after 1 week).
Once the RH is below 20% ALL THE BOWLS ARE DRY ENOUGH TO TURN. Usually 3 months on a freshly felled oak, poplar, or ash.
Fruitwoods take longer as do really dense woods (dogwood and persimmon come to mind, the persimmon took 1 year)
IF YOU WANT A BOWL KILN, GO FOR IT!


----------



## TomC (Oct 27, 2008)

thisnobody said:


> CLICK ON THE LINK BELOW FOR EXPLANATIONS
> http://s925.photobucket.com/albums/ad99/thisnobody/Dishwasher%20Bowl%20Kiln/
> 
> The explanations are in the descriptions of the photos.
> ...


Are you saying the persimmon took a year in the kiln?
Tom


----------



## TomC (Oct 27, 2008)

TomC said:


> Are you saying the persimmon took a year in the kiln?
> Tom


Another question about persimmon, I can get I believe it's 2" by 2" by 12" for $1 each locally. How does it turn and what does it look like?


----------



## thisnobody (Mar 17, 2010)

In the Kiln at a normal schedule, yes the persimon bowl blanks which averaged around 10" with a ~1" wall thickness took around a year to get below 12% (EMC in my area [SC]). The 2"X2" would probably take the same.
Persimmon is one of my favorite woods to turn. It turns easily even though it is very hard, Polishes up to HIGH GLOSS with minimal effort. Wish I could get it more often, just not a lot of people removing the trees.


----------



## TomC (Oct 27, 2008)

thisnobody said:


> In the Kiln at a normal schedule, yes the persimon bowl blanks which averaged around 10" with a ~1" wall thickness took around a year to get below 12% (EMC in my area [SC]). The 2"X2" would probably take the same.
> Persimmon is one of my favorite woods to turn. It turns easily even though it is very hard, Polishes up to HIGH GLOSS with minimal effort. Wish I could get it more often, just not a lot of people removing the trees.


Upstate SC. I'm in NC less than 20 miles north of Gafney, SC.
Tom


----------



## thisnobody (Mar 17, 2010)

> Upstate SC. I'm in NC less than 20 miles north of Gafney, SC.


I am 25 miles from Gaffney in Duncan, SC. 
Where are you getting wood from in that area, just curious.

TED


----------



## TomC (Oct 27, 2008)

thisnobody said:


> I am 25 miles from Gaffney in Duncan, SC.
> Where are you getting wood from in that area, just curious.
> 
> TED


Mostly from Advantage, they are out of Buffalo, NY but also have a place in Earl, NC. It's just north of Blacksburg, SC. I am getting some 12/4 green cherry next week from a local sawer. If you look on the net Advantage Lumber has a mailing address of Grover, SC but they are just outside of Earl.
Tom


----------



## Midlandbob (Sep 5, 2011)

Interesting thread. I have been turning for years and just use shelves in the garage then move to the house shelves in 3 months. I usually have more than enough through the system but the kiln would be good if you did not want to inventory a lot of bowls.
Do you get any increase in splits to failures? I always thought slow drying to allow for the deformation was important but it seems like you are speeding things up.
I did the microwave thing with thin vessels but it seemed to add an increase risk of error.
How hot are the boxes?


----------



## TomC (Oct 27, 2008)

Midlandbob said:


> Interesting thread. I have been turning for years and just use shelves in the garage then move to the house shelves in 3 months. I usually have more than enough through the system but the kiln would be good if you did not want to inventory a lot of bowls.
> Do you get any increase in splits to failures? I always thought slow drying to allow for the deformation was important but it seems like you are speeding things up.
> I did the microwave thing with thin vessels but it seemed to add an increase risk of error.
> How hot are the boxes?


I wanting to be able to dry some blanks for pepper mills. I bought several blanks at Klingspor. They were all coated in wax. Most were OK when turned. I had one that was to green. It looked good when turned but now the top will not turn because the hole in the top and the tenon on the bottom are both egg shaped. I will post pictures when kiln is completed.
Tom


----------



## thisnobody (Mar 17, 2010)

Midlandbob said:


> Interesting thread. I have been turning for years and just use shelves in the garage then move to the house shelves in 3 months. I usually have more than enough through the system but the kiln would be good if you did not want to inventory a lot of bowls.
> Do you get any increase in splits to failures? I always thought slow drying to allow for the deformation was important but it seems like you are speeding things up.
> I did the microwave thing with thin vessels but it seemed to add an increase risk of error.
> How hot are the boxes?


I do not thimk ant of the splits/checks/crack that I get (minimal) would not have occurred if I were wax and waiting. The key is to kepp the humidity up in the box while the wood needs it. Lower temp in the begining and stepping it up as time goes by. The Humidity is what keeps the wood from checking. The temperature allows the air to hold more water. 

CHECK OUT THE INFO HERE
http://www.fpl.fs.fed.us/products/publications/specific_pub.php?posting_id=13141  There is a great begining course for drying by numerous methods out on the web, but I really only trust the people who do it for a living. The guys at FOREST PRODUCTS lose thou$ands if their drying process is wrong, not just a couple of bowls.

My temps start in the 85-95 F with humidity at 80% or so for weeks 1-2 or up to a month if needed. When the humidity starts to drop 10% or so I move the temp up 10 degrees or so. Once the humidity in the dishwasher is at or below 20% I am good to go (12% is EMC for me). I have got the humidity to below 10% before but the wood deformed in the middle of returning a box as it picked up moisture form the air. 
Balance is key.


----------



## TomC (Oct 27, 2008)

*Kiln Completed*

Attached are pictures of my home made kiln. It an old upright freezer and is heated by a 100 watt light bulb. It has a thermostat that will control temperature up to 110 degrees F with a three degree dead band. I have an indoor/outdoor thermometer to know the inside temperature. I drilled two holes at the bottom; one for a vent and one for the power cable for the light. I did the same at the top; one for a vent and one for the thermostat. I packed the power cord and thermostat holes with insulation. Now to try it out.
Tom


----------



## TomC (Oct 27, 2008)

*Additional Pictures*

More pictures


----------



## TomC (Oct 27, 2008)

*Kiln Loaded*

I noticed that one of the cherry slabs that I had purchased had started to crack. Upon looking at it the pith was in it. I cut it up and loaded the kiln yesterday. It took several hours for the temp to come back up. Currently it is at 85 degrees( also set for 85 degree) and 75 per relative humidity. Some water on floor next to kiln, leaking out of door seal.
Tom


----------



## thisnobody (Mar 17, 2010)

Hey TomC
Water coming out of the wood is good, out of the door seal not so much.
I have a fan blowing in the dishwasher that circulates the air in there.
A dishwasher has built in small vents for the drying function.
I believe small amounts of moisture escapes when I turn on the fan thus reducing the water leaking out.
In your case a small drip pan may be in order.
Once the wood gets completely warm it will act a s a heat source itself, reducing the heat recovery time.
All in all it looks good, you'll love the kiln for bowl rough-outs.

Do you know a farrier in your area Andy Painter ?


----------



## TomC (Oct 27, 2008)

thisnobody said:


> Hey TomC
> Water coming out of the wood is good, out of the door seal not so much.
> I have a fan blowing in the dishwasher that circulates the air in there.
> A dishwasher has built in small vents for the drying function.
> ...


It for sure is drying the wood. I am not worried about the small amount of leakage on the garage floor. I did open the door to make sure the bottom was not full of water and it wasn't. I did have the vent at the top and bottom partially blocked off with tape. I have them fully open now. The current conditions are 83 degrees and 89 percent relative humidity. The wood has been in there less than 48 hours. I have no idea how long it will take. I expecting to see the relative humidity to drop as it dries. I'll take any advise or info that you want to share.
Tom


----------



## rsw49 (Jan 13, 2013)

Robert Rosand did a one page article on a "mini-kiln" in the AAW journal back in June 1995. If you are a member you can access the article on the AAW website in back journals. I made one similar to his. Basically a box out of styrofoam insulation board with a light bulb as a heat source. A thermometer with a probe to install in the box and I used a light dimmer switch to dim the bulb to get the temperature I wanted.I used 90 to 100 degrees I believe. One whole side of my box was removable to remove items. Also I did not put a vent or fan in my setup. Every time the box is opened the outside cooler air enters the box and the warm moist air exits. The inside air is then heated lowering the relative humidity and drying the wood. I did not put green wood in mine usually. I just put air dried wood in I wanted get a little drier before making a project. I assembled the box by cutting panels of the insulation board and gluing together with construction adhesive. I doubled up the board so the walls are about one and one half inches thick. For the light I bought one of those ceramic light sockets and mounted it on a board. Pretty easy to make and works well. Rich W


----------



## Syd Sellers (Feb 2, 2013)

*Vacuum Kiln*

Has anyone considered the advantages of a Vac Kiln. Shorten your dry time to hours...


----------



## TomC (Oct 27, 2008)

Just got the first load of wood out of kiln. It took longer than I thought it would. However, less than 4 months is better than a couple of years for 3" cherry to dry. I will get it reloaded this week. I had to disconnect the thermostat because I could not get the temp up to continue the drying process.
Tom


----------



## thisnobody (Mar 17, 2010)

3" thick square blanks will take a couple of months, but I agree that is much better than 3-4 years of waiting.
The real advantage is the bowls drying in such a quick manner without defects.


----------

