POTS FROM THE FIRST FIRING

I am posting some pieces from the first firing that show the effect of ash and a little soda on the glazed pots. There is a mixture of stoneware, white stoneware and porcelain in this firing so the surfaces are mixed in terms of how the glazes are being influenced by the color of clay under them. Some have more ash intertwined with the glaze and these pieces were closer to the firebox. I was pleased and surprised by the surface effects that I attained in this first firing.

First Firing Done

The first firing is done and the results were mixed. The front 1/3 of the kiln came out great, the middle third was OK but somewhat cool and the back never got to the temperature I wanted it to achieve. The firing took 15 hours which includes a 4 hour preheat with gas to cure the arch keystone and the back wall top inset. I learned that with this kiln less wood per stoke is better than more as it is easy to choke it up with too much wood. Also, the front air intake required less air than I anticipated. There are 4 air intake ports on the bottom front and I ended up using the two middle ones. My biggest problem was even distribution of heat which is not uncommon for a wood kiln but I think I crammed it too full and did not allow enough room for heat flow front to back. It was fairly even in terms of heat from top to bottom in the front and middle of the chamber. I used a little salt at the end and it combined with the ash deposits on the clay nicely.

The next firing will be stacked a bit looser and with less little stuff crammed everywhere. Also, there were some pieces of castible on the surface of the top pots so I need to work the loose bits out of the margin between the last bricks on the inside top of the arch and the cast keystone. I will post some pictures of the finished pots in my next posting.

First Firing

The morning of the first firing I looked out to the garden and look who was watching! A very large Red Tailed Hawk sitting on the gatepost to the entrance of the garden. What a magnificent animal. I am hoping that he/she is a good omen for the upcoming firing.

LOADED

The kiln is loaded and the door is stacked. Next is the first firing. It didn't hold all of the pots I made for the maiden voyage but, honestly, it holds more pieces than I imagined it would. I will candle this first firing with propane for about 6 hours until I am sure the castable is cured. It has been sitting under a metal roof for almost an entire South Carolina summer so it is as dry as it's going to get but I will fire it slowly the very first firing. Fingers Crossed

LOADING THE KILN

Everything is made, bisque fired, glazed and now it is time to load the kiln. Transporting the pots down the hill from the studio to the kiln was a bit of a task and there were a few casualties along the way, but all is here now and ready to go into the kiln chamber. I am uncertain as to how many pieces this new kiln will hold, so I made more than I thought would fit in the interior, but we shall see. The actual placing of the pieces in the kiln begins tomorrow.

WOOD

In preparation for the first firing I am gathering and splitting wood. You can see two bunches of split wood in this post -- one is a pile and the other is stacked under the woodshed. It is a mixture of oak, hickory, pine, poplar and cherry plus a bunch of small pieces of dressed wood for my side stoke hole. They say that wood heats you four times; once when you cut it, once when hauled, then when you split it and when it burns. I would add a fifth time: when you stack it in the south in the summer. The good thing about wood firing in the south is that we will never run out of pine in my lifetime. My neighbor Dave brought over an oak tree from his son-in-law's yard with his front loader that was about 30" in diameter in places. It gave me a new appreciation of tree service workers. Now on to glazing!

Pots for the Kiln

Here is a picture of pots that are in process for the first firing. They are stoneware, porcelain and white stoneware...various clays around the studio. I am making more pieces than is probably necessary as I don't have a good idea how many pots this kiln will hold.

The Kiln is Done

The kiln is finally done!  There are now lots of pots to be made for the first firing and wood to be cut and split.  You can see the supporting steel is in place and the metal rods are tightened to the point of light tension.  I have included some detail shots of the side stoke port, the bricks that line the side and the ports for pyrometers.  

The side stoke plug is an idea I got from Michel Bayne, a local potter and friend that cast his port and plug using terra cotta flower pots.  Michel is a very fine clay artist working in the Edgefield tradition. 

The pyrometer ports will contain porcelain tubes that will act as shields for the pyrometer's two thermocouples, one placed next to the front stack and one near the back.  They will measure the temperature during the firing along with pyrometric cones.

Final Stucco Coat

The final coat of insulating stucco is attached the outside surface of the kiln.  It covers both the bricks and the layer of kaowool blanket and both help to keep the heat in the kiln.  I anticipate that this will need patching and covering after each firing as the kiln expands and contracts during the firing process.  Next the steel is attached -- I am almost there and it is time to make pots for the first firing!

Woodshed

The wood shed has been attached to the kiln shed and the bracing has been attached to both sheds.  I am ready not to be on a ladder for a while and working over my head and with the sun gleaming down on sheet metal.  But we had rain almost every day last week  and the wood shed roof, which goes slightly under that of the kiln shed creates quite a run off when the rain comes down.  I will eventually attach a gutter and hook that up to a rain barrel for the garden.  Next comes finishing the outside stucco and attaching the steel bracing to the kiln.

Insulating Blanket Coating

The kiln now has a coat of Kaowool, a spun clay material that has an insulating quality and can withstand temperatures in excess of 2000 degrees F.  This material is similar to the tiles that cover the surface of the Space Shuttle and keep it from burning up during re-entry into Earth's atmosphere.  You can see from the photo that on the kiln it is held in place with wire which will also act a surface to grip and hold a coat of A.P. Green refractory stucco insulation that will cover the outside of the arch and further help to retain heat in the kiln during firings.   

Finishing the Chimney

The chimney is done at last.  You can see by this photo that the structure rises 14 feet above the level of the kiln floor and required using my neighbor Dave's scaffolding to put the upper parts of the stack in place.  Cody and I came up with the brick detailing at the top for a little fun at the end of a challenging part of the kiln's building process.  We also finished attaching the last elements of the roof in place and made flashing for the space between the roof and the chimney.  The damper is enclosed in the stack(where the chimney corbels in to a smaller diameter) and will help control the amount of draft the kiln will draw during a firing.

Arch Brick in Place

          These photos show the arch brick set in place and ready for the keystone to be cast.  The keystone ties the arch together and creates downward pressure on the arch brick "setting" the arch.  You can see my son Cody casting the keystone using 3000 degree F castable refractory.  Also included is a photo inside the arch form that holds the brick in place.  Once the keystone material solidifies then the arch form is removed revealing the inside of the arch.  After this the kiln's back wall and chimney will be built.

Working on the Arch

Work on laying the arch Brick has begun and, suddenly, a snow!  My black lab Bewley was helping and she enjoyed the evening working on the kiln very much.  This is slow, steady and painstaking work. 

Arch Form in Place

The arch form is now in place and ready to receive bricks to make the chamber of the kiln.  This is a catenary arch--approximately as wide as it is tall but not a round arch form like a roman or barrel arch.  If you take a piece of string and let it drape loose it will create a catenary arch..  This arch is almost 12 feet long and three feet tall.  The form is made from a skeleton of 2" X 4"s and 3/4" front and back plywood shapes with 1/8" Masonite streached across the form and screwed into place.  Look for the bricks to define the arch next.

Ready for the Arch

The walls that support the arch form are in place and ready to accept the wooden arch form that the bricks will be laid upon.  All is as level as I can get it and yet I find little places that vex me.  Such is the world of the brickmason.  I am trying to imagine the interior of this space filled with fire and pots glowing at a temperature of around 23oo degrees F...  Soon! 

The kiln floor is now established and the first layer of the side walls is in place.  These walls will be four bricks high before the arch begins.  I have an interesting collection of fire bricks new and used so it becomes an puzzle solvers task to find enough bricks for a course that are the same size. 

Firebox

Now the firebox is complete up to the subfloor level.  Getting the floor on the block base and the firebox level to match up is a bit of a trick...it takes some patience and a lot of bricking up and then moving bricks.  Once all of this is level then the floor is next!

Firebox

The firebox is being laid in front of the block base that now has a layer of firebrick on top of it.

The aluminum foil is a moisture barrier between the block and brick and between the first layer of softbrick at the base of the firebox.

The block base has been laid in place for the kiln.  Next will come the brick and the firebox.  

Shed is up

The shed for the wood kiln is now up and in place and withstood the big wind storm that blew through here two weeks ago.  Wasn't that a mighty storm!  Good thing is it provided my neighbor's pine tree for the wood pile.  What is 36 hours without power compared to wood for the kiln?