Pit kiln

[caveman]

Long story short I got some clay from digging in the back yard. I got to thinking about it and did some research I am going to explain what I did what happens when I fire it.  I am open to suggestions feel free I have a lot to learn

Ok so I took the information I had from research and life added water shake vigorously and......poof a hole in the ground I shall name it pit.......

The pit is 50 cm by 75 cm and the depth is 50cm except the center it has a large piece of fireplace on it keeping the floor at about 50cm and under it it goes deeper I used forced air and put old gas pipe in at angle and on the end I put a shop vac set for blow. I made a lid for it but it was unsuccessful I took fire brick and lined a piece of metal roof I think when the air was on I had a gap between the brick and metal where I had a rectangle hole in it I think the air currents. I probably not explaining it well. So I only used a full lid once normally I would stack brick and stone to cover over about a quarter of it.

Firing 

I would take what ever I was going to fire in the bottom some wrapped up in newspaper some naked then I would kindle then some pieces about 4 cm thickness stack on it I would light it but wouldn't turn the air on I would over fed the fire almost choking it out I would have a lot of partial burnt wood once I had about 10cm of it on the bottom I would start the air and add wood lots of wood and watch the flame change color from red to blue and white I would keep it going for about 2 hours then I would leave it and come back the next day and dig out (and hope alot)the things and pieces. 

I did a lot of experimenting and once I covered the fire with dirt when done took a lot longer to cool. The time I had a lid I had a piece of slate from the roof in small spot to keep heat from the pipe I didn't want the pipe to get hot enough to melt the end of the shop vac  well I melted that piece of slate some of the pieces of clay looked like kinda melted and if I was sharing kiln space I would have had a lot of people upset the whole inside of the pit was now a nice bright terracotta color if someone please explain what happened there (figured it out iron in the dirt when I covered it was left behind)

The brick in the bottom is not mortared in I take apart the bottom when I clean it out then restack it back for next time after the big piece is back I use broken pieces of fired clay like lava rock that way the air comes out defused more even i will add photos in my albums tomorrow when I have better light. All it is a hole lined with brick air pipes in from bottom . 

If this was your backyard what would you do differently? 

Can I use cones in it?

How can I make a top for it? Can it be made for next to nothing?

What would you try if you where not afraid to fail? 

[neilestrick]

Are you trying to do a traditional pit firing, or are you trying to use the pit as a kiln? Photos won't load, and I won't totally understand what you've done until I see the photos. But a typical pit firing does not use forced air, and if you're trying to do a typical pit firing then I wouldn't mess with it at all. That air is what's causing the  kiln to get too hot in some areas. You just don't have any control over how hot or evenly a pit will burn, so  it's best to just let the fire do its work on its own, as it won't get too hot if you just let it burn. As soon as you introduce air flow, whether from a fan or from natural draft like a chimney in a wood kiln, you will increase the temperature that the kiln can reach. Without proper controls to manage the air flow and a way to measure the temperatures in the kiln (cones or pyrometer) you won't have any idea what's actually going on in there and you'll get hot spots and cold spots, especially in a pit that not's evenly insulated and doesn't have any real direction for the air flow.