# Kiln from and old refrigerator?



## Knothead62 (Apr 17, 2010)

Bad news- our old refer in the basement went out! The good news- I can convert it to a kiln for small pieces of wood. It is about a 16 cu. ft. refer with a freezer at the top. The interior has two shelves and more can be added, if I can find some to fit the brackets. I plan on taking the compressor, etc. out and scrapping them. I figure on putting one or two light bulbs in the bottom and running a piece of metal pipe through the freezer and top as a vent. I can use the extra freezer space as storage- can't waste valuable space! What do I need to complete the job? Should I keep the magnetic door seals?


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## hairy (Sep 23, 2008)

That is something I have considered, but that's as far as it got. Here's some links that maybe you've not yet seen.

http://www.woodturningonline.com/assets/turning_articles/Kiln/Introduction.html

http://www.rudieswoodwork.com/kiln.htm


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## hairy (Sep 23, 2008)

You might want to think about leaving the compressor and refrigerant plumbing intact. There are some strict laws concerning venting refrigerant, it also can be unsafe to remove the compressor without the proper equipment.

Old refrigerator disposal is also regulated by EPA laws.

Basically, all your old refrigerator has to offer is an insulated box.


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## wmodavis (Aug 28, 2007)

An integral part of a wood dryer is air movement. IMO you need some sort of fan to keep the warm air circulating through the wood. The well insulated refridg should allow you to maintain the elevated temperature for drying. Good way to recycle the unit.


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## 33706 (Mar 5, 2008)

Hey, Knot,
Why not just simply convert a clothes dryer, instead?


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## Knothead62 (Apr 17, 2010)

PK, the dryer still works!
Hairy, I'm thinking that there is no freon since the compressor runs but no cooling in the ref or freezer. It is at least 20 years old and I'm thinking that there is a leak. I'm not going to dispose of the refer, just the non-working parts.
Bill, good idea. Need a fan at the top to pull air bottom-to-top.


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## TopamaxSurvivor (May 2, 2008)

I would use a small heater on a thermostat for the heat source. More efficient than light bulbs. Maybe a crock pot heater from the thrift store. Natural convection through the box should move enough air. If you use a fan, the heat source will not do you much good unless it comes through a heating source or the ambient temp of the intake is high enough. I doubt is the ambient temp of the basement is high enough to provide the heating????


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## wmodavis (Aug 28, 2007)

Maybe a small heater and thermostat would be better but I think youy are wrong on the fan. Most everything re drying wood in a kiln is based on significant air movement. You have to bring dryer air in contact with the wood you are drying and once it has picked up the moisture from the wet wood you have to move it away or the wood will not continue to dry. Air circulation is a very important aspect of a dryer.


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## TopamaxSurvivor (May 2, 2008)

With a fan, you will definitely need a bigger heater than light bulbs or a hot plate element to keep any amount of volume heated in a lower ambient temp.


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## wmodavis (Aug 28, 2007)

My dryer is about 4×4 x 8 ft and uses 6- 60 watt incandesent light bulbs. They get the heat up to a peak of about 120 deg F when all are on, Right now they are off to keep the RH at my desired level. The two fans run continuously to keep the air moving. With the heaters off it runs about 90deg. Right now I'm maintaining a RH of just under 60% to get the wood to about 11% MC. With no fans you will have a hard time removing moisture from the wood. But maybe it would be just the right conditions for your wood. If I was you I'd definitely consider a fan if I wanted dry wood.


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## TopamaxSurvivor (May 2, 2008)

What is the ambient of the area you have it in? I assume the fans are not recirculation, they are changing with outside air, eh?


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## Knothead62 (Apr 17, 2010)

Ambient temp in the garage today is 54 deg. F.  This is cold as I live in SE Tennessee with 8 inches of snow today. Area has heat/AC tied in with the rest of the house. Summer time temps are mid-60's as part of the basement/garage is underground. House is a split foyer on a sloping lot. It isn't a big deal to plug in a heater to bring the temp up a few degrees. I'm thinking of using the fan on the compressor to draw air up out the top like a power burner set-up. I could take off the magnetic seals or rig up something to keep the door cracked.
Bill, I would think that the moist air would be drawn off the wood and taken care of by the heat pump. right now, the air is dry; static electricity is very evident.
*Thanks to all *for their replies and advice. I'm in no hurry and will do some more research to see what fits the bill here.


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## wmodavis (Aug 28, 2007)

Here's a good source of info.
http://www.woodweb.com/cgi-bin/search/search.cgi?Realm=All&Terms=drying#reference


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## wmodavis (Aug 28, 2007)

A couple of good articles.
http://www.fpl.fs.fed.us/documnts/fpltn/fpltn-199.pdf
http://www.extension.purdue.edu/extmedia/FNR/FNR-155.pdf

Here is a quote from a good article on drying.
"Air Movement
If the air surrounding a piece of wet wood is stagnant and of small volume, it will soon become saturated and evaporation of moisture from the wood will stop. Even when there is a continuous stream of air passing over the wood the layer of air in immediate contact with the wood will move more slowly and have a higher vapour pressure than the main stream. This is known as the 'boundary layer effect'. With increasing air velocity in the main stream this effect decreases and evaporation rates from the wood surface increase, particularly when the air flow is turbulent rather than laminar. An increase in air speed can therefore be regarded as equivalent to a reduction of the humidity barrier near the wood surfaces.

Since air passing through a stack of wet wood gives up heat and takes up moisture it is bound to be cooler and more humid where it emerges than where it enters and the drying rate is therefore slower on the air outlet than on the air inlet side of the stack. The faster the air speed and the narrower the stack, the smaller is the difference between the two sides. For this reason fairly high air speeds are desirable in a drying kiln, particularly when the timber being dried is very wet and loses its moisture readily. In most modern kilns the uniformity of drying is further improved by reversing the direction of air flow through the kiln load at regular intervals." 
(from:http://www.mtc.com.my/info/index.php?option=com_content&view=article&id=35%3Athe-theory-and-practice-of-drying&catid=31%3Atimber-drying&Itemid=46&showall=1)


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## Knothead62 (Apr 17, 2010)

Bill, excellent articles and information! Thanks. Your second post is reminiscent of the principles of convection cooking. Move the static moisture layer that is over the product and it cooks faster. I was working on my shop yesterday and ran across a fan/motor combo. I think I can rig it up at the top to pull air through the main box and out the top. I'm going to hook it up first to see if it can run continuously.


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## wmodavis (Aug 28, 2007)

The two fan's I use in my dryer are the radiator fans out of a Toyota. They are made for much more extreme conditions than my kiln but will definitely withstand continuous running in a potientially moist environment. Since they are 12 Volt I'm using an old computer power supply that I had laying around. They whip up a good breeze inside. They were from a used auto parts place.

If the pieces you are going to dry start out pretty green you need to be careful and remove moisture slowly at first. Coating the end grain and/or maintaining a high RH inside will help prevent damage. Adding heat is a way to speed the drying process because it lowers the RH and the moisture evaporates faster when warm. Even with cooler internal temperatures you should keep a fan moving the air around for more uniform results. I monitor the temperature and humidity and control them the best I can without too much fancy stuff. I am using a cool inexpensive data logger help keep tabs on what's going on though. 
Also my chart 'to live by' in drying wood is from Hoadley's book 'Understanding Wood'. 








If I'm starting out with pretty moist wood I start with heaters off, fans running and high RH. I gradually bring down the RH until I decide to speed up the process by adding heat. That reduces RH and accelerates drying. A key is knowing the wood's moisture content, the temperature & RH hence the logging device. I'd rate it as a fun and productive thing to do.


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## TopamaxSurvivor (May 2, 2008)

Data logger isn't working Bill. Is is a temp and humidity recorder?


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## wmodavis (Aug 28, 2007)

"A data logger (also datalogger or data recorder) is an electronic device that records data over time … either with a built in instrument or sensor or via external instruments and sensors."

Choose your name. Call it what you want. It measures and records data (temperature, humidity) for display and analysis so that adjustments can be made to correct and control the process of drying wood without which you would be relegated to the 'seat-of-the-pants' method.


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## Garry (Oct 5, 2006)

I made a bowl kiln awhile back out of a side by side refer that my neighbor gave me.
I use the fan that the refer had and 100 watt bulb which maintains a tempature between 90 and 100 
F this time of year here in the north.
I tool about 2 weeks to dry a 15 inch roughed out bowl of cherry.
It was well worth the trouble.


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