Sunday, April 4, 2010

E-Z Bake Kiln

After 10 years of hard continuous service, I felt that it was time to replace my old kiln with a new, thermostatically controlled model that could be loaded without being a contortionist.

The concept behind the kiln is the same as the old E-Z Bake ovens, without the undercooked cupcakes. By using 300-450 watts worth of light bulbs (sorry, no green bulbs here, we need the heat!), the box easily heats to 120-125 degrees before the thermostat kills the power. Below is Seth putting the box together. We simply made four L shaped legs from strips of plywood and joined them with a strip of wood along the top and about 16" off the floor. The bulbs are house in the space below the lower strip.

To isolate the lights from any combustables, we ran a baffle made from aluminum flashing that hangs directly over the bulbs as well as some aluminum screen to keep debris from the bulb area. The strips of wood support the wood being dried. We used 1" thick celotex insulation to infill the box.

The most common questions that I get about drying wood are, "Do you put it in green?" and "How long do you leave it in?". I avoid putting any green wood in the kiln until it has had at least a couple of days to air dry. If the pieces are larger than spindles, I try to go even longer. Basically, leave parts out of the kiln as long as you can stand it.

As far as the amount of time to leave the parts in, a very accurate way is to weigh the parts and to leave them in until they stop losing weight. This means that they have come to equilibrium with the air in the kiln and will dry no further.

Another factor in drying wood is air movement. This is essential to allow the moisture laden air to escape. Without air movement, the kiln would just be a sort of low power steam box. If I had wanted to get fancy, I could have use some sort of fan or space heater with a fan to get the air to move, but I just rely on hot air to rise and a number of holes in the top of the kiln for air to escape. I also use some holes in the top to set the legs in to dry their tenons, so by having a few extra I get all the air flow I need.

If I was trying to be more gentle in the way that I dry my parts, I'd run the fan with the temperature lower at first and then step it up later. But for me, the air drying does the trick. Besides simplicity, I also like to keep the temp up in the kiln so that I can "set" the wood in my bends at the same time that I am drying other parts.

Here you can see that I used steel "high hat" channel to mount the lights. I wanted to isolate them from contact with any flammables.

Below is the chicken incubator thermostat that controls the power. I have it mounted in the top inside of the kiln. It does a fine job and for cheap! Here is a link to a page on ebay where I bought one.

Here are couple of other kilns. While teaching at Kelly Mehler's School last month, we cranked up the heater in the bathroom and rigged up some racks. It worked just fine. Normally during summer months, the students just use their hot cars, pretty smart if you ask me.

Here is the kiln that Kelly has for smaller parts. It's the same concept, but without the insulation.

Drying green wood that has been split into small parts is a whole lot simpler than I could have imagined before doing it. If you imagine leaving a piece of bread out on the kitchen counter, and how long it would take to go stale and become rock hard, then you can get the timing of drying a spindle.


gregoire68 said...

Welcome back. Thanks for the contact for the thermostat. I've looked in farm stores from TN to FL and no one had any. I did finally learn how to soak and bend kiln dried white oak with great results. I'll try to send some pics of the outcome. Greg

Peter Galbert said...

Thanks Greg,
I'd love to hear more about your process with the oak. The thermostat works well, I guess if it's good enough for the chicks, it'll do for us!

Chuck sallade said...

I was just checking out your post from 2010 about your new kiln. I am in the process of building one, and was curious about youe experience with "regreening" kiln dried woods, i.e., white oak. Do you know of any one who has done it? Have you? If so, what were the results. I live in an area with no useable green hardwoods....Ugh! Any advise would be appreciated. Thanks

Peter Galbert said...

I was just talking to my Aussie friend about the same issue. I'm afraid that I'm no expert in this process, but you might be able to find info on some of the woodworking forums. I've heard of soaking the wood with a bit of fabric softener or multiple steamings, but some research and tinkering might get you through it. Please let me know if you come across a workable solution