help with new (to me) Duncan kiln

[Cinthia]

Today my boyfriend surprised me with a Duncan ES820-2 with an LT-3K kiln sitter that he bought on facebook marketplace. The person he bought it from told him it works great, and it looks to be in decent condition. The max temperature it’s labeled for is Cone 8. I generally work with stoneware and fire my things to Cone 6, which should be possible in this kiln but I’m a bit worried about that after doing some research. 

I have a handful of earthenware bisque pieces that I was planning to glaze and have that be my first firing experience with this kiln, but all my previous kiln operating experience is with automatic kilns. SO, to get to the point of my post, I’m wondering how long to set the timer for? I know that if all goes to plan, the kiln will shut off on its own once it reaches the maturity temperature of the pyrometric bar (cone 06), but I want to set the timer for somewhere near the actual amount of time it will take. 

Basically, any advice you can offer would be greatly appreciated. I do hope to use this kiln for my mid-fire temp work, so tips for that as well would be appreciated!!

[neilestrick]

Ideally, the timer should be set for about 1/2 hour longer than the firing will actually take. That way if there's a problem with the cone it will shut it down before it over fires very much. The only way to know for sure where to set the timer is to do a firing with the timer set too long and see how long it takes. Set it for 10 hours, do the firing, see where the timer stops, then math it out. Make sure you use the same settings and/or turn-up schedule every time you fire. You'll also need to test for a glaze firing, too, as that will probably take longer. Test with the kiln full, as that will affect firing times in a manual kiln. It's an imperfect system, but it was the best we had for many decades.