Category Archives: Soda-firing

Soda, Clay and Fire: a new book on soda firing

It is finally here, Gail Nichols’ new book on soda glazing: Soda, Clay and Fire. This book is based on her research from her PhD in Material Science on Soda Firing at Monash University (Australia). I just got my copy from Amazon (click on link to order)- so I don’t feel like I can actually review it yet. But I wanted to share with you that it is finally out in print. There is still so little information published on soda firing/ glazing- this literally doubles the number of books published exclusively on the topic.

Also, in my neglect of my blog recently, I have not mentioned on here that 500 Pitchers came out in the spring. I was lucky enough to get another 2 images published in the latest publication from Lark Book’s 500 series.

A Study of Continental Clay Bodies

I have recently done a little study of the high fire clay bodies from Continental Clay in Minneapolis. I made teabowls out of each of the clay bodies, and fired one in c. 10 reduction and one in soda (also c. 10 reduction). They are both glazed in a luster shino glaze which shows off the differences in the clay bodies beautifully. The c. 10 pots are glazed both inside and out with the shino glaze (left). The soda pots are glazed on the inside, and on the rim (right). There are 9 clays that I tested in total- so keep scrolling down… Enjoy!

**be sure to click on the images to see a much larger image and really see the details.**

 

Soda Firing Workshop with Emily Murphy

Soda Firing Workshop

with Emily Murphy

Interested in soda firing?

 

This workshop is the whole soda firing process packed into
one weekend at Lillstreet Art Center.

 

This workshop is for intermediate and advanced students, amateur potters, and professional ceramic artists who want to have an introduction to soda firing or to expand their soda firing knowledge. Workshop students will learn how to load the soda kiln: no kiln loading experience necessary!

Soda firing is an atmospheric firing that produces flashes of color, a textured orange peel surface, and reacts in a variety of ways with different slips, glazes and clay bodies. The “soda” in soda firing is a combination of baking soda and soda ash. The soda mixture is introduced into the kiln near the end of the firing. The soda vaporizes and is carried on the flame throughout the kiln. Wherever the flame travels, the soda travels and reacts with the pieces in the kiln to create a glazed or flashed surface.

Come to the workshop with an assortment of bisqued pieces. Variety is best. Please come with 6 – 10 pieces. You’re not guaranteed to get every piece into the kiln, but we’ll try to get in at least 6 pieces, depending on size. The more variety of forms, sizes, shapes and clay bodies, the better for loading! The clay must be rated to Δ10. If you’d like to purchase some of Lillstreet’s special soda clay body ahead of time, you can make arrangements for that. You will be contacted via email prior to the workshop with suggestions of commercially available clay bodies, as well as some slip recipes that you can mix to use on your greenware.

Friday, April 21, 11am-6pm

We will meet to get an introduction to soda firing, glaze, slip and wad pieces. When the pieces are glazed, we will load the soda kiln with everyone’s work.

 

Saturday, April 22, 5-7pm

Saturday is firing day. This timing is approximate- we will be mixing up the soda and putting it into the kiln around this time (Δ9).

Monday, April 24, 3-6:30pm 

Unloading time! We’ll unload the kiln and examine our results from the soda kiln.

 

Lillstreet Members $135 / Nonmembers $140

Soda Firing lab fee: $30


To sign up for this workshop, go online to lillstreet.com, or call: 773.769.4226

For more information about the workshop, or to learn more about Emily’s work,
please visit: sodafired.com or email: emily@sodafired.com

 


What is soda firing?

This post is part of a handout that I give to my soda firing students at Lillstreet Art Center. It is an attempt to explain a little bit about the history of soda firing, and tries to help answer the question, “what is soda firing?”. It is not the full story, but I hope that you find it helpful.

Soda firing is an atmospheric firing technique where “soda” is introduced into the kiln near top temperature (2350°, ∆10). The soda that we use is: sodium bi-carbonate, also know as baking soda (the Arm and Hammer™ kind), and sodium carbonate, which is also known as soda ash.

“Soda ash is the trade name for sodium carbonate, a chemical refined from the mineral trona or sodium-carbonate-bearing brines (both referred to as “natural soda ash”) or manufactured from one of several chemical processes (referred to as “synthetic soda ash”). It is an essential raw material in glass, chemicals, detergents, and other important industrial products.”
USGS

The soda vaporizes and is carried on the flame throughout the kiln. The soda vapors create a glaze when it lands on a piece (or a kiln post, or the wall of the kiln). Wherever the flame travels- so does the soda. When placing the pieces in the kiln during loading, you have to think carefully about when and where you want a piece to get lots of soda, or when and where you want a piece to be more protected. The kiln must be evenly loaded because the flame will travel on the path of least resistance (and therefore the soda will also be traveling on the path of least resistance). You also have to think about whether or not the piece is glazed. The soda is basically a glaze, and when two glazes mix, they can react chemically with one another and run down the side of the piece. It’s beautiful when you can control the run- but can be disastrous when it gets away from you!

What is the history of soda? Where did it come from?

The predecessor of the modern day soda firing, is salt firing. It is believed that salt firing began in Germany in the 13th century. As many things go, it was most likely come upon by accident. Perhaps some salt soaked wood (from pickling barrels?) was tossed into the kiln for the wood fuel. The salt vaporized and glazed the pieces inside the kiln. It was a great time saving measure. No need to glaze the pieces before they went into the kiln. Old German jugs were salt glazed, along with tankards and sewer pipes. The pieces that we think of as early American traditional ceramics from the southwest corner of the US were also salt glazed. Can you picture a big whiskey jug with cobalt blue decoration on it? Those were salt fired. The process that I’m talking about is wood firing with salt thrown in. The salt easily glosses up a piece and helps the wood ash flux out. Salt vaporizes at a fairly low temperature and can work its way into all sorts of nooks and crannies. In a salt firing, the salt vaporizes and the sodium chloride splits into sodium and chlorine gas. When the chlorine is exposed to moisture, it forms hydrochloric acid. The acid goes into the kiln atmosphere and is released from the chimney. The remaining sodium combines with alumina and silica in the clay to forming a glaze on the surface of the piece.

Although the previous paragraph doesn’t help sort out what soda firing is, it does give some important background information. Salt firing continued to be a technique used by potters up through the 1970’s (and is still is used as a firing method today). In the 70’s as people became more aware of the environment, they realized that the black smoke and hydrochloric acid wasn’t such a great idea. A couple of graduate students from Alfred University, NY studied sodium alternatives to salt firings, hoping to find something that was more environmentally friendly, and maybe even something that could happen in an urban environment.

The results were soda ash and baking soda. They produce carbon dioxide instead of hydrochloric acid. The soda doesn’t get into all the nooks and crannies like the salt does, but it does produce brighter and more vivid colors. Pots are usually glazed with an interior or “liner glaze” because the soda vapors won’t work their way into those hard to reach places. You can achieve a rich glossy surface that is heavy with soda, or a pebbled surface that is also referred to as an “orange peel” texture. This is often juxtaposed with a “drier” area of the clay that wasn’t hit directly with the soda. It’s all of these varied surfaces together that make up the rich look and feel of a soda fired pot. 30 years ago, when soda firing first began, most ceramicists were just trying to mimic the effects of salt firing. In the last 5 years that has changed. The true characteristics of soda firing are unique and are something to explore and achieve.

The soda vapors aren’t actually colored, but they are reacting with the alumina, silica and iron in the clay (and slips) to create the various colors of flashing, and associated textures. The resulting colors can be a range of oranges with yellow and red tones, to rich browns, golds and tans. If there is some copper in the kiln, there can be pink blushing. Or a cobalt glaze on a piece can cause a blue twinge to the soda. Sometimes the carbon from the firing can add a gray hue that can look like shark skin on porcelain.

So perhaps now you know a little bit more about soda firing.


I’ve included the recipe that I use for my soda firings below.

My soda recipe: (a variation on Gail Nichol’s process)
2 lbs. soda ash
3.5 lbs. sodium bi-carb
5.5 lbs. whiting (calcium carbonate)
Mixed with ½ of a 5 gal. bucket of wood chips, and water

*mix the dry stuff with the wood chips, and then add COLD water. Just enough so it sticks together. It should have a consistancy similar to oatmeal cookie dough or tunafish salad.

-Add soda into kiln when ∆9 is soft. Add 1 ½ angle irons full of soda mixture through each port. Wait 15 minutes between additions. Usually takes 3 turns to add in all of the soda.

Mark of the Flame

Throughout the Spring session at Lillstreet Art Center, my Advanced Topics in Soda Firing class worked on putting together an exhibition of their work- from developing the idea of the show, to producing the work. I’m really excited about the direction this project has taken. The results can be seen at the opening of the exhibition on July 16. Please see below for more information.

The idea of the exhibition is that each set or series of pieces was designed and placed in the kiln to intentionally mark the surface with the pattern and shadow of the flame. All the pieces are fired in the soda kiln, where the soda vapors are being carried with the flame. The results of this are some really exciting pieces that tell the story of how they were made. Photographs of the pieces in the kiln (like the ones seen below) will accompany the displayed ceramics. Please click on image to see it larger-and to read all the details.


The opening reception is Saturday, July 16th at Lillstreet’s Gallery in Chicago. There are several openings happening at the same time- it should be quite an event! If you need directions- please click here.
I hope to see you there!

“Soda Fired” Mug

This is the sort of mug that I think of when I think about what a soda fired mug is. Warm, rich coloration from the flashing. Orange peel texture built up on the high points.

This is also a soda fired mug:

John Norris has come up with this hilarious idea. It’s a standard, industrial produced mug with the image of soda firing wrapped around it. It’s the “perfect” soda mug.

I enjoy the cleverness of this, but it also helps remind me what I’m doing making handmade pots in a world of industrial pots. Making something that is beautiful in surface and form; designing a form that is not only visually pleasing, but ergonomic. And perhaps most importantly, making a human connection between the maker and the user.

I came upon this essay, “Potters, the Values of Craftsman, and Living True to Self” by Nathaniel Pearlman on his blog: Political Mammal, and I encourage you to read it. It puts into words another reason why potters make.