Getting ready to put together a kiln

[iowabow]

That's awesome would be very helpful to the community here to have that material list. Maybe after you post that we can have this post pinned. I heat treat in kilns that cost thousands of dollars as part of professional development and with ceramics. For flint knapping proposes you have assembled a real nice highly useful produce at a low price. Can you also list the cost of the components. I live 30 mins from Bartlett instruments they have a produce simular if I recall but geared toward ceramics and glass. The owner, Dave, is a freind of mine and donated their lastest ceramic kiln controller for me to Beta test. I don't think for our purposes that expessive controllers do anything more on the functional side (other than display feature) than what you have assembled.
I ABO heat treat myself in a pit out in the country with wind fall from our woods but not everyone has that kind of direction, space or access so your kiln redesign is going to be very helpful to a lot of people. Having control of the ramp is a huge advantage and means guys dont have to worry so much about cracking material and if you are buying stone it will pay for itself in short order. I will post here in a few mins the cook i did for Tower's black novaculite stone.

[iowabow]

I put his novaculite on a 10 degree ramp to 190 then a 24 hour hold then 10 degree ramp per hour  to 750 with a sink rate at 10 degrees per hour. This will take a week. I isolated the rock to normalize the temp change as seen in the photo and placed a kiln shelve over the rock. The rock was isolated so to speak.

The big issue with novaculite is popping so it has to move slow. The 10 degrees per hour is very slow in my opinion. The 750 is on the safe end the longer time will do more heat work
Keep in mind that heat work is different than temp. The longer time means you dont have to go as high. If you go high faster you dont need as much time. But dont go fast with novaculite better to be safe. I believe he thought this was cooked about right if memory serves me right. The size of his stone was a factor as well.

[iowabow]

The isolation aspect was an insurance idea in the event of a power failure due to thunderstoms or power spike. This would retain energy/heat and maybe prevent it from cracking.  Power issues disrupt  the ramp controllers. My Beta test model has a resume feature that will continue the firing in the event of a short power failure.

[Huntrick64]

That is interesting that you mentioned the power interrupt.  This PID has 3 options you can program in the event the power interrupts.

1.  Resume at whatever point you left off
2.  Restart at step 1.
3.  Simply stay off

The power is rarely off where we are cooking so we chose the default (option 1).  We chose this because probably 3 out of 4 times there is a power interrupt, it just blinks or is off only a few minutes.  Resuming where you left off in these cases is OK, and having to start over every time this happened would be cumbersome.  But if the power was off 12 hours or more, the temp would drift down low enough that jumping right back to max temp might happen too fast for the rock.  I think if we are cooking at a time when we think the power might be interrupted (like during a thunderstorm), we would just have to manually shut it off if we lost power for an extended time.  The best setup would probably be to have one of the larger Uninterruptible Power Supplies (UPS) like you have on a computer (file server) and program the PID to simply shut off if you loose power.  This way any blip in power or outage that lasts less than an hour or two would be covered by the UPS and the PID would run as normal.  If the power was out long enough to drain the UPS, the PID would simply shut off and stay off.

Regarding cost, the ramp/soak PID, SSR, Heat-Sink, and Thermocouple were something like $110-$120.  I bought a $30 project box that I would not buy again.  We gave $50 for our broken kiln and the total we have in this thing (including the kiln, the things mentioned above, and a switch, indicator lamp, wires, relay, connectors, etc.) was $239 total.  If you didn't need the ramp/soak feature you could deduct about $40 from the PID.

The most impressive part of this whole deal (in my opinion) is that we are doing this with only 920 watts of heat in that kiln, and it doesn't have to fire the element that often (guessing 20 percent).  I think using the two center existing coils (wired serially) was great for initial cost and efficiency.  The coils we are using make 6 complete wraps around the center part of the kiln.

It has been a crazy week because my daughter's wedding is today.  Maybe next week I can take time to document this a little better for others who want to try this.

[iowabow]

Very cheap very cool project.

[caveman2533]

Be careful to not let the thermocouple touch the rock. It will cause the temp to rise  beyond what the rock is rising and will cause overheating.

[Huntrick64]

Good point caveman, and that makes sense.  I protect that probe like it was my own personal probe.  No banging it on the rocks, no smashing it between rocks, keep it clean, and pretty much, nothing touches it, ever.
 

[iowabow]

Be careful to not let the thermocouple touch the rock. It will cause the temp to rise  beyond what the rock is rising and will cause overheating.

for correct heating keep it a couple inches from any mass