Wood Firing Process Described

There seems to be an endless symphony of factors when firing a wood kiln. I feel lucky to participate & learn from Dan Barnett, who seems to have perfected the process; in regards to efficiency and sustainability, while keeping the treasured visual effects of wood firings in tact. All the while, he is making tweaks & learning from the process.

I want to preface this with stating that I am not an expert on wood firings but an enthused participant. Firing and glazing chemistry is something that has to be learned over decades & is something that one are never truly done learning.

My goal here is to give you a taste of the process, complications, challenges & beauty of this style of firing.

A little technical background/ context on kilns, firing types & my process can be found at the bottom of this page, if you are interested.

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Throughout the firing, we constantly stoke or feed wood to the kiln in order to raise its temperature.

There is a natural raise & fall in temperature that I think about like waves.

As the wood burns it creates gases that burn off and cycle through the kiln, creating this wave in temperature.

We track it both with a digital pyrometer and with cone packs to inform when and how much wood to add to the fire boxes.

Adding wood at the correct moment is crucial. If you add too much wood or add it too quickly, it gets overwhelmed. Not enough wood causes the box to go cold.

We use wood from dead or fallen trees on Dan’s property. They are split and dried for about a month. Primarily Oak but we use a bit of Pine that burns faster and hotter.  

One of the markers of a wood fired pot is the slightly glossy & darkened spots. I call these marks of the flame. Near the end of the firing, we add sodium and potassium carbonate to the kiln. As it vaporizes and moves through the kiln, it will leave marks on the pots. There are various methods to do this but we soaked wood in this mixture and added it to the fire boxes.

In order for all the work to get these special effects, there must be great flow in the kiln. Learning how the air and flames move is extremely important. Manipulating that flame starts when you are designing the kiln and informs how the kiln is loaded.

There are still many factors that I have not touched on such as, wind, change in atmosphere, how tightly the kiln is loaded, moister in the wood, ect...

I hope you find this interesting— Here’s to life long learning!

x Molly

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Read more about Kilns, Firing Types & My Process:

All kilns have a heat source & a desired temperature goal. The clay and glaze of all of the pottery inside a given kiln is designed to mature or vitrify at these particular temperatures & shrink at a similar rate in order to “fit” together. Ceramicists measure these temperature in cones; you may hear terms like “mid fire” which refers to cones 4-6 or “high fire”which is generally cones 9-12.

High fire kilns are generally found in community spaces because they are much larger, requiring many people to fill them. They have a heat source such as gas or wood, often featuring a specialty or atmospheric element like soda. Work that comes out of these kilns is generally earthy and muted in color.

I learned ceramics primarily from old school potters who LOVE high fire glaze & heavy reduction. Reduction is a slight starving of oxygen from the kilns atmosphere. It pulls oxygen out of the glazes, darkens the clay body, and causes other beautiful effects.

Electric Kilns are growing in popularity, largely because of convenience but they are also very efficient. With programmable computers that carefully monitor and control the kiln, optimizing the process. Electric kilns generally fire much cleaner with a neutral or oxidized atmosphere, resulting in much brighter, cleaner glazes.

It was not until the start of Covid-19 that I began to work in electric or mid fire ceramics, re-imagining my work to fit these new materials and firing method. I’d been glaze firing all my work at a community studio that shut down for many months. I am extremely grateful for this push. I have learned so much from it and now have much greater control of my production process. That being said, specialty firings are a great treat!