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A SIMLPE KILN

A while back I figured out that turning green wood is a lot easier than dry wood and more fun. But I am too impatient to wait a year for the turnings to air dry. So I built a small Kiln which works very well; I thought I would take a few moments and share this build.Here it is, not very pretty but the kiln is effective. I can generally dry a green bowl in 7 to 14 days depending on type of wood, thickness and moisture content. I try and leave the sides and bottom of the bowl three quarters and one inch thick. At this thickness the wood dries uniformly and there is enough thickness to remove any warping.

Using three quarter inch plywood I built a box about 48”W x 48”T x 30” D and lined the inside with 2” insulation and added a couple racks using scrap wood.

For heat I use a 75 watt light bulb; wired the light through a thermostat. The thermostat is for a water heater; I glued a piece of aluminum about 12” square to interior wall of the Kiln so it would heat up and activate the thermostat. I used and old deep fryer basket turned up over the light to disperse the heat, and eliminate hot spots.

The Kiln is wired with an exterior switch and plug in. I used a fan from an computer storage server, it is low voltage and I happened to have a cell phone charger at the voltage output, works great.

Next was the dehydrator, the on I am using is for a gun safe or a closet and uses electrical charged plates to condense the moisture in the Kiln. The first piece I dried cracked and warped beyond use. I realized that the dryer was too fast so I used a lamp timer to turn the dehydrator on and off at selected intervals.

To be able to see what was going on in the Kiln I used an indoor weather station with a remote sensor. This way you will be able to see temperature inside and outside and the humidity both inside and outside.

It is important the keep a near constant temperature throughout the drying process. With this set up I can keep the temperature at 86 to 92 degrees, and this will vary some. The humidity will start high and slowly decrease. The Kiln works best with several pieces in it; if I have only one wood bowl I will put in some random wood in to create a load on the Kiln, fire wood works great. You can also add a small pan of water over the heat source.

It is very important to monitor the wood daily for weight this is the only way you can tell when the wood is dry. I have included the records from the Maple bowl pictured earlier is this post. You can go to http://www.wood-database.com/ to get specific information about the wood you are working with. Sometimes I cut a test piece of wood; 1 board foot of the same thickness as my project. The Wood Data Base will give you weight per cubic foot at 12% moisture content; divide by 12 and that will be the weight of the test piece when it reaches 12% moisture content.

Shoot me an email with any questions.

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Bio: I am a retired Forester and have worked in Forest Management and Construction for 45 years. I love wood turning especially exotic wood, shape and ... More »
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