Kiln Openning

The kiln finally cooled enough to open by un-bricking the door. Here is an overall view of the ware.



The front part of the kiln was loaded with Amy's plates. Below is the kiln half unloaded.



Here is what a clone pack looks like from the other side of the spy hole. The cone bending is cone 10, the one still standing is cone 11. This is in the top of the kiln in the back. On the bottom, cone 11 was down hard.



Rob's face jugs, Amy's crock and Jody' test tiles.



The glaze on the test tile to the far left is "Salt Shino" from John Britt's book, the one to the left of it is "Oatmeal" from Mark Issenberg. The rest of the tiles are glazed with "Bird Matt", a glazed that is a standard at the Appalachian Center for Craft. The difference is the amount of Cobalt Carbonate added. Tile #3 0%, tile #4 0.5%, tile #5 1%, tile #6 2%, tile #7 3%, tile #8 4% and tile #9 6%.

Fire!

The salt went into the kiln starting at about 3:00 AM and we closed the kiln in and went to the house at about 3:45. But that is the end of the story, lets back up a bit...

After having finished bricking in the door at about 10:00 PM the night before, Rob got up and was out to the kiln at about 5:45 AM. Amy and Rob took the first shift and fired through the morning. Jody came about 1:00 PM and was greeting by the other occupants of the farm.



The kiln was already started to breath a little fire.



On the basic level, firing a wood kiln is simple. You pick up a bundle of wood, open the door and put the wood in.



and repeat, and repeat,



and repeat, and repeat, and...



As night closes in and the kiln reaches about 2000 degrees, it becomes a fire breathing dragon.



It was beautiful to see the moon rise over the valley while hearing the roar of the kiln.



While the stoking is easy, but tiring, getting to the right temperature is a little more complex. You need to find a balance between the amount of cool air you let in through the "mouse" holes, the amount of wood you put in, and the amount of hot gases you let up the chimney by adjusting the dampers.



You keep track of it by watching the cone packs via "spy" holes and tracking the temperature with a probe (thermocouple) and a pyrometer. This is a view of the pyrometer.



Below is a plot of the temperature measured versus the time spent. The kiln takes between 20 and 22 hours to reach the desired level of heat. The plot shows that the rise in temperature comes quickly early on, but it really goes slowly towards the end. The rate of stoking and amount of wood added goes way up also during those last 200 to 300 degrees of rise.



However, at some point in the wee hours of the morning, it comes time to add the salt to the kiln. Shown below are views of how the salt is added. The salt used here was a "meat curing" blend obtained from the local Co-Op.



The tool to put it in the kiln is a pipe cut in half. The salt is measured out and poured along the pipe.



With the dampers closed down, the stoke hole is opened up and the pipe inserted over the coal bed. The pipe is then turned over and the salt falls onto the coals. The salt breaks down into its components, sodium and chlorine gas. The gas goes up the chimney and the sodium seeks out the silica in the clay, reacts with it and forms a glaze.



At this point the firing is done. We close up the kiln and go home. We pass by the trailer loaded with the wood to be cut for the next firing. Ugh, lets think about that next week.



Following soon will be the kiln opening...Christmas time for potters!

More Loading

The glazing and loading usually goes on for a couple of days. It always seems to be rushed. Each time you swear you are going to plan ahead, get things done well ahead of schedule, but...it seldom happens that way.

Rob and Amy in the process of loading.




The shelves used are two sizes, 12 x 24 and 24 x 24 inch. Here Amy is moving one of the big shelves into place.



The post we use are sections of brick. One of the issues with salt firing is that the salt glaze goes everywhere. If you do not use a material that will not accept the glaze, all the bricks, shelves and ware will glaze together. So part of the loading process is "wadding". This means placing balls or logs of the material between everything. This material chips or grinds off after the firing. This is the white material you can see in the picture below.



Here are the plates after they have been glazed ready to be loaded.



We are always looking for that perfect glaze. Shown here are test "tiles" ready to go into the firing. The tests this time are for two new "recipes" from other potters and a series of the same base glaze with the amount of the coloring oxide, cobalt carbonate varied. There are so many variables in making a great glaze, you have to test, test and do more tests.



Here is a view in one of the "spy" holes. The "cones" you see are manufactured to consistently bend when the have been heated a given amount. We judge if the clay has hardened enough and the glazes have melted by watching these.



We also use a pyrometer as can be seen by the box to the right. This measures temperature through probes into the kiln. This gives an instantaneous view of how things are going versus the long term view provided by the cones.



After all the loading is done, the door is closed up by stacking bricks.



And now its on to the actual firing, which started very early this morning at about 5:45 AM. Now, which is 10:30 Am the temperature in the kiln is 690 F in the top and about 400 F in the bottom of the kiln. In the beginning, the temperature is often quite different top to bottom, but as the end gets closer, the temperatures get closer. Off to take a shift at stoking!

Glazing and Loading!

Well, as is usual in life, events conspire to delay - the firing has moved back a day until tomorrow, September 8, 2009. Glazing is nearing completion and the kiln will be loaded today. Following are a few pictures of the glazing and ware.

These are Rob's Face Jugs:



Almost all the glazes used in the wood firing are made on site from base minerals. This is a snapshot of the glaze "Lab".



Glazes are applied by brushing, dipping, pouring, or spraying. Sometimes, to get a aesthetic look glaze is applied over an area and then portions of it removed to expose the clay.



This firing is going to have a large number of platters. They are stacked and ready to be glazed as they go in the kiln. They are going to get an "ash glaze" made from wood ash and clay.



These are fermentation crocks, glazed and ready for loading.



Stay tuned! More to follow.

Update Date

It looks as if the next firing will be September 7th instead of the 6th.