Firing a Wood Kiln for the First Time
If building the wood kiln was an odyssey, firing the wood kiln for the first time was a 5K obstacle course sprint! There was so much to do beyond just throwing wood in the thing.
Before I go any further into my story I have to tell you what a wonderful team of support friends we had helping us. Our neighbor Alex, who is a true renaissance man when it comes to building things, volunteered to build the fiber and iron door. The door had to fit snuggly, be completely removable, and include a small hinged door for feeding the fire box. We owe him so much pottery to say thank you for how well the door turned out.
Metallurgy is the subject of study and work for a very dear friend of ours, Will - we really did win the lottery when it comes to friends. His advice, and access to thermocouples was invaluable. Plus - he volunteered to work a very long shift over night on the first night of the firing. This was a huge gift as it was driving rain in 35 F temperatures almost all night.
Master potters and friends volunteered to fire the kiln with us including: Randy (who worked most of the 28 hour firing), Amy (who took the early morning shift with me), Will, as well as master posters - Laura, Nikolas, and Sam.
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You can put unglazed stoneware into a wood kiln firing since the ash will turn to glass on the pots at those high temperatures. However, Josh and I were just so excited to try our own glazes that we picked 8 to make from scratch two weeks before the firing. Did we have all the ingredients? Nope. Frantic calls around town and pick ups from several locations and we started dipping our pieces in these glazes - with no testing!! We really just went for it.
After making the glazes we carefully split all of our ceramic work into groups and took turns dipping and wiping each and every pot. It takes quite a lot of pottery to fill a wood kiln and we knew that using untested glazes was a huge risk - plus glazing all that work took hours and hours.
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Our studio is a wonderful little space inside our home, but the wood kiln is about an acre away down a winding trail through our yard. Each and every pot had to be packed up and carried down to the kiln. Then each pot had to be sorted to determine placement in the kiln. Loading a kiln is rather like loading the car for a long road trip, a bit of Tetris like expertise is needed. It takes time and thought. What makes this process more difficult is that each piece must also be fitted with small balls of a material called wadding along the base. This wadding prevents the pot from becoming permanently glued to the shelves during firing. That wadding has to be mixed fresh and will fire with the pot and then be discarded as the kiln is unloaded. What makes this process exhausting is that each piece of pottery has to be loaded into the kiln by someone sitting deep inside the kiln across the firebox hunched over and fighting a spinal cramp that would make a normal person cry. Needless to say - it took hours. Normally you would load the kiln the day before you fired it to get some rest. We are not normal people.
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The kiln was loaded, the kindling was lit - the fire had begun. Wood kilns use heat from accumulating coals to reach temperatures in the thousands. At these temperatures ash from the wood liquifies and adheres to the pots in the kiln. The colors achieved depend entirely on the amount of oxygen available to the fire. Starve the fire of oxygen and it will pull oxygen out of the pots and the glazes on those pots. Thus firing a wood kiln is a process of feeding and starving the coals of oxygen to achieve the colors you desire while also continuously and more frequently adding more and more wood.
Preparing to feed a fire for this length of time we accepted any offers of free firewood. In fact, one of the greatest expenses in firing a wood kiln (other than time) is on the purchase of firewood. We are so grateful to everyone who offered us their firewood for free. After transporting the lumber to our house we spent weekends splitting it into small sections that would fit through the kiln fire box door.
Marie is splitting logs in preparation for the wood fire.
The door of the wood fire kiln a glow in the darkness.
We said we would wait a week for it too cool off before unloading it. Then we said we would just take a little peak. Well only a few pieces to see if the glaze worked. Before you know it was had three tables out there on a Wednesday afternoon with the kiln unloaded and us late for our dinner date.
There was a feeling of dread when we first opened the kiln. Everything looked so dark, so dirty, gray and ugly. Did we stop to early? Should we have fired for longer, or slower? Hopes were high and at first we weren’t sure. Due to the loss of the thermocouples we had been depending on the pyrometric cones placed throughout the kin that we could spot through small viewing holes in the kiln walls. These cones were hard to see clearly due to the red hot glow of the kiln and some guesses were made. As we unloaded we searched for these cones.
The front of the kiln had gone over cone 10 - the maximum temperature for the clay we were using. However, as we moved through the kiln some areas on the side had reached cone 12 while the back had not reached cone 9. It was a disappointment, but a learning experience. Uneven heating of the kiln produced uneven results across the kiln from front to back and side to side. In future firings we will need to use air flow from front to back to transfer heat more evenly through the entire kiln.
The Results.
We lost 5 pieces out of hundreds. Although many of the pieces did not look the way we had been hoping, to lose only 5 is such an impressive number we have declared this firing a huge success. Those 5 pieces lost their balance due to being hit with kindling, or by the flow of air through the kiln. As they tipped and fell they struck other pots and were stuck together. So if you are in the market for three cup all pointing different ways - I have a deal for you!
Thank you to everyone and I hope to see you at our next firing in the Fall of 2022!
Starting the fire in a small pile of kindling in the wood kiln.
Weighing and mixing 8 glazes 2 weeks before our first wood fire. Did we test the glazes? Nope.
Joshua is loading the kiln once piece at a time, one shelf at a time from back to front.
Firing the Kiln took 28 Hours.
Overall firing the kiln went very smoothly. Driving rain in 30 degree temperatures, snow at sun rise, melted thermocouples, and emergency wood splitting - all of these things were handled with a laugh as we pushed through from around 7pm Friday night to the early hours of Sunday morning. Volunteers of friends and master potters arrived at even intervals to help - all eager to see and be involved in the process of firing such a large kiln. We found that it took 3 people to manage the kiln at a time. One to throw the wood in, one to lift the door, and one to offer assistance either handing wood, moving wood with a metal poker, or supervise for safety.
Wood was added to the kiln at shorter and shorter intervals. At first it was every 15 - 20 minutes, in the early hours of Sunday morning it was every 4 - 5 minutes. Just enough time to catch your breath and cool your face before facing the fire again. Yes the kiln was that hot! Just being near the kiln was enough to melt the faux fur lining of my coat hood!
Inside the freshly opened kiln. This kiln cooled for three days before it was opened and unloaded. Usually it takes a week to cool, but unusally cold temperatures made cooling occur much quicker.
Cups, vases, bottles and more from the wood fire kiln - Spring of 2022
