woodfire kiln

[iowabow]

I have not fired this kiln yet but here are a few little details on the design . The flue cross section is 10 percent of the area of the fire box, the inlet flue is the same, the kiln is about 7 cu ft (might be about 300lbs of flint) in relationship to a 13x 25 inch fire box. The chamber and the firebox match proportionally to larger wood fired kilns. There will be two flame deflectors before the heat reaches the material. The chimney only has about 3 feet of sideways draft and no downward draft so the chimney purpose is only to clear the shed. I increased the percents on the inlet and exit flue do to scale.  The rational is that the openings change in size but the molecules don't. If you have any questions please ask and suggestions are welcome.

[leapingbare]

I still don't understand how your going to control the temp to allow for ample drying time. at 240*
and be able to hold the temp at a steady 600* for the 8 hour soak.

[iowabow]

Well yes that is an issue. With ceramic woodfire it is done manually.  This will be the exact same process.  Pyrometer will show the temp and a stoking pattern will become evident based on size of wood and type.  I will be able to tell you much more about the function on Monday.  I hope to have a pattern that will allow me to step away during the firing.  There will be shifts that the operators will sign up for.  This way I can get sleep during the process.  It is labor intensive but it is a hobby kinda like building a bow the hard way. It would be possible I think to do the 240 that drives off water then take a break and continue the process 8 hours later. The temp might be 100 if it is buttoned up tight. Or I might be able to take the temp up before the break and then let it drop during the break to 240.   Not sure how this will work out.   But I regurlarly fire with wood and don't sleep for 30 hours anyway it will be fun.

[iowabow]

I also thought that a propane burner could be used if more control is needed.  I will be test firing tomorrow I still have some parts to install.  Also I was wondering if anyone has experimented with reduced vs oxidized environments as it relates to heat treating flint. 

[iowabow]

Here is the finished product.  It is kinda a frankenkiln

[mullet]

It'll work, I do it with a $5 Black and Decker Toaster oven.

[iowabow]

Ok first test complete run up to 2400 completed in 3 hours. Next test is the 200 degree hold.   I will do this test tomorrow.

[iowabow]

The test for control hold was difficult today because the kiln is so highly efficient. The solution will be a controlable inlet flue.  This will allow the rate of climb to be restricted.  The kiln will fire to 400 degrees with 5. Dowel rods  1/2in in dia and 14 inch long.  It is unbelievable how efficient this kiln really is. This is why it will be easy to control with the modification.  After I figure out what the design of the damper will look like I will post a picture. I fired the kiln with pottery and it fired to 2300 in 4 hours and burnt about 16 logs 6in in dia and 16 in long.  You would have to see it to believe it and I would not have believed this if I read it on the internet

[Jaeger]

how hot will a  trash can get in the full sun ,would it do a light heat on some rock ,I am just curious some of the flake I get out of a tin trash can seem to work much easier than they did  when I put them in there as debitage on that rock when I broke it open ( raw perd). maybe a painted black tin trash can covered with a window pain , would it do a light heat ?

[iowabow]

I read some where that you can use charcoal to heat treat with. This is an interesting idea to heat treat with solar I would think you might need to insulate the can so that the heat would not escape. But the problem would be maintaining a sustained temp temp for the period of time you need.

[leapingbare]

need to get to about 300* to get any chang, most rock needs about 500* +

[iowabow]

I have been doing experiments with the woodfired kiln lately and thought I would update you on the progress.  Most of the work has been about high heat range around 2300 degrees. The interesting information for PA is in the preheat phase.  As leapingbare stated earlier control would be a problem for flint.  This was also a problem for the ceramic projects as well.   To solve this problem I switched to propane for a more uniform low heat source.  I can turn on the burner and walk away for an hour at a time and maintain a 200 degree temp.  I have not heat treated any flint yet but will when the weather cools.