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2. Neutral to Oxidation Atmospheric Soda Firing

9/17/2019

 

Interview: Jason Bohnert

Cone 10 Oxidation Soda Fire Glazes:

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Cone 10 Willie Helux Glaze
(high luxury remix of Helix Glaze)
 
Nepheline Syenite      39.68g
EPK                             11.11g
Silica                           30.16g
Whiting                        19.05g
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​Add:
Copper Carbonate     1.2g
Black Copper Oxide  5g
Bentonite                    2g
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Cone 10 Turquoise Oribe Glaze

            

Bone Ash 1.94g                                
Strontium Carbonate 9.36g
Talc 3.98g
Whiting 17.87g
Custer Feldspar 28.53g
EPK 3.23g
Flint 35.09g
​
​Add:

Copper Carbonate 6.67g
Bentonite 2g

Information about his firing techniques:

Why did you choose oxidation soda firing over reduction soda firings?
"My work in the soda kiln relies on contrasts between the warm tones of raw clay and flashing slips with yellow, orange, and red hues and vivid cool colors of copper glazes.
Using varying glaze recipes and proportions of Copper Carbonate and Copper oxide, along with some Red iron oxide and cobalt, I am able to achieve a range of greens, blues, and purples in a neutral/oxidized atmosphere, once past body reduction. If I continue to reduce the kiln beyond body reduction, especially a heavy reduction, some of these glazes would turn mauve, pink, and red hues, with some blistering, elephant skin, and/or pinholing."
 
How does the color in oxidation soda firing differ from reduction soda firing?
"The copper saturate glazes (intended to go green to blue) use between 2-6 or even 8% copper, compared to a Copper Red Glaze, which may only use between ¼-2% Copper Carbonate. Such glazes, in reduction, will not blister or pinhole, and turn a clear to vivid deep bright to blood red hue when fired and applied properly. The Copper Saturate Glazes are not meant to go red, and need a cleaner, neutral to oxidized firing atmosphere to achieve the greens and blues. With the addition of soda in the kiln, the green and blue glazes often appear brighter and have more of a range of colors from the added flux."
 
What Kilns or burners are the easiest to do oxidation soda firings?
"I have used both venturi style and forced air, although forced air gives you the most potential for control of air to gas ratios. Wood kilns can easily achieve the ideal neutral atmosphere for these copper saturate glazes as well, but care must be taken not too over reduce during glaze temps. The wood-fire practice of reduction cooling is NOT kind to these Copper Saturate glazes and will almost guarantee extreme blistering, pinholing, and unattractive mauve hues. Avoid these glazes if the goal of the wood firing is reduction. I fired in a cross-draft catenary arch style wood kiln with these glazes and achieved beautiful results."
 
How do you even out a kiln without going into reduction?
"The active damper is your friend to achieve even pressure inside the kiln. Using the riostat (blower fan speed adjustments) and air flaps (air volume regulators) along with gas lever (gas volume control), one can balance gas to air ratios, maintaining a neutral/oxidized atmosphere (or whatever atmosphere is desired). I mostly fire in cross draft style kilns, so, in general, pushing the damper in moves the heat to the top; whereas, pulling it out encourages heat to rush across the floor and out exit flues, heating the bottom. Using the damper and reading flames out the bottom spy is a standard gauge for even pressure inside kiln. I like to have a tiny lick of flame out the bottom spy to ensure I have enough for even temps, but not too much, which could stall the climb in temperature or create unwanted reduction."
 
What kind of glazes are best in oxidation soda firings?
"I use a lot of shino, amber celadons, blue celadons, temmoku (iron saturate) and copper saturate glazes. When using Copper Saturate glazes in a soda kiln, I typically avoid using them as liner glazes, due to inevitable crazing and the potential for leaching with acidic foods/beverages. Especially when using barium or strontium to brighten copper blue glazes, I keep them on exteriors for color pop, and leave safer glazes on interiors."
        
What’s a typical firing schedule for you, including when do you add soda?
"I typically load and light day 1.
I will light one burner for several hours, before lighting the other, and then do a turn up or two before bed, allowing a steady preheat.
About 5 am I begin hourly turnups until body reduction, which I begin at cone 012/010. I do increase gas and push damper in further and continue body reduction until cone 08 is down. Now I begin increasing the air, using riostat and flaps, to clean up atmosphere to neutral and use damper to create desired pressure (tiny flame out bottom spy). This continues through heating, adjusting air and damper while monitoring evenness top to bottom, until cone 9 begins to fall.
At this point I prepare soda to introduce, dry first, then sprayed, until desired amount is used up. The dry soda ash or baking soda is mixed equal parts with soda, whiting, and wood chips/sawdust, and mixed into a thick paste using minimal water, then smeared onto bark or small wood slabs. These are stoked into kiln every 15-20 minutes until gone. I wait until cone 10 is down and sometimes spray some soda ash in water at end, then shut down kiln."
About Jason:
"I was born in Louisville, KY, did graduate studies at West Virginia University and in Jingdezhen, China, and now reside in Flagstaff, AZ. I’m a Senior Lecturer in the School of Art at Northern Arizona University, where I teach design, drawing, and ceramics. I make pottery at my home studio, which I designed and built myself between fall 2017-present. My work explores organic forms and the architectural details of the vessel. Hues and textures I experience in the natural world are evident in my ceramic surfaces, created from atmospheric firing in wood and soda kilns. I am interested in the shared moments handmade pots can create through daily use, during communal wood firings, shared meals, and rituals of coffee and tea. All wood and soda-fired work is fired to 2400 degrees and is very durable and food safe. Studio visits are welcomed by appointment - Message or email me to schedule."

Learn More about Jason's work on:                           
Instagram
Etsy
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Soda Firing Workshop Review

8/28/2019

 

Did you know that I travel to teach workshops?

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I wanted to share some of the reviews from my most recent soda firing workshop I taught at Community Arts Center in Wallingford, PA. This was a 5 day long workshop.
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​Here are quotes from my students feedback:

"Lisa:
-Very Organized
-Very open and relaxed
-Made everyone feel welcome and included
-Enjoyed Powerpoints for clarity and organization
-Worked hard to make us a cohesive group with humor
-Enjoyed our ending discussions/critiques"

"Lisa, I have learned a lot about the whole process of soda firing and because of that I  will start making pots more intentionally for the kiln. Liked combination of lecture slides, demonstration, and doing."

"1. Loved your Manner, Knowledge, and introducing us to loosening up on wheel thrown pots. It’ll be nice to venture away from the round!
2. Really appreciated your organization skills (slide presentations), and reminding us to be good stewards.
3. I hope you’ll come back soon! Your energy and Enthusiam are wonderful!"

The biggest critique was not enough glazing and making time...I might need to turn this into a longer workshop next time!

Ps. Community Arts Center...thanks for hosting me, and fostering such a wonderful work environment and amazing students. Also your students have no idea how lucky they are to have a soda kiln on a double hinged door. Click here to see video of using door!
Feel free to reach out for more soda firing workshop opportunities in the future. My next workshop will be in Minot, North Dakota in October, and stay tuned for more opportunities to work with me in the future.
If you like soda firing, make sure that you are on my email list to stay up to date
​on my soda fire educational series. Click the button below to join.
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​Why are my pieces warping in the soda kiln?

8/16/2019

 
Ps. I do read your messages, and thought I would answer this readers questions here on my blog so that all of you could learn from it too.
 
Question:
“I would like to hear your thoughts on wadding. For example, how many wads per pot, how large or small the wads should be, what shape they should be, where exactly on the foot should they be placed, etc?”

Typically I use 3 wads for everything. Exception 1: I have a 5-sided piece and I want to echo the pattern by placing a wad underneath each corner. Exception 2: the piece is wide…I then use more wads to support the piece.
 
Pea-sized wads are the size wad I use on almost everything. For heavy pieces they might be more like grape sized wads (mostly so they don’t get squished totally flat under the weight). But it’s also an aesthetic choice…you could use bigger wads or use a cookie cutter to make different shapes…I’m not interested in doing that for my work right now.
 
Wad placement should be under the “foot.” This is more obvious when you have a foot ring. When there is no foot ring think about where there is a change in direction from vertical to horizontal…ie where most of the pots weight would go on a counter top.
 
Question:
“I think wadding ties into my other area of curiosity--warping! I am focusing on making wide and low forms lately, like planters, and I am wondering the best way to wad them. Should they have an inner and outer ring of wadding? Is that overkill, or necessary to inhibit warping? Should I even be firing these wide low forms in a soda kiln if I am trying to avoid warping?”
 
Yes, wadding can contribute to the issue of warping. I recommend placing a wad about every 2-3 inches along the foot ring of really wide forms such as plates and platters. If wads are placed too far apart it can contribute to the problem of the ceramic piece warping. Another thing to consider is when stacking forms, such as plates, wads should be stacked in alignment with wad above wad. Think about loading a kiln. Posts need to line up one above the other to put less strain on the kiln shelves and carry the weight down through the posts to the floor of the kiln. There are many causes for warping that are not related to wad placement.
 
The way you make and dry a ceramic piece is usually the guiltiest culprit for warping and cracking. More compression and even drying in my opinion is the solution to most clay problems. Spend more time with a rib compressing a slab or bottom of a low wide pot. In general, you will have greater success having a shallow curve and foot ring for a bottom of a wide piece than adding a second inner foot ring. Warping could also be related to needing to leave that bottom a little bit thicker. In addition, a piece may have started to warp because of uneven  drying depending on the piece this may not become apparent until the final firing.
 
Another solution is addressing the clay body. Certain clays will warp like crazy when fired slightly above cone 10. Adding a grog could also strengthen the clay and reduce its chance of warping. So you may need to look for a different clay body to use that’s better for low wide forms.
 
All forms are more at risk of failing in a soda kiln over an electric kiln. Don’t be discourage…I fire lots of low wide forms in the soda kiln. To Sum it up it’s a matter of problem solving the combination of these elements: better shape, compression, even drying, clay body, and wad placement.
 
Please keep sharing questions you might have about soda firing. If I can't answer your question I'm sure I can find an artist to interview to answer the question for both of us. Plus it might be a topic in my soda firing educational series just waiting its turn to be release.

5 Techniques for Cleaning Up Soda/Wood Fired

8/15/2019

 

Pot Needing Work

Tool for the Job

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DIAMOND CUT OFF WHEEL FOR DREMEL
​​Purpose: to cut off wads that have fused to pot.

Watch video on how to use diamond cut off wheel by clicking button below.
Video: Diamond Cut Off Tool
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DIAMOND PAD FOR POTTERS WHEEL
Purpose: to level bottoms of pots.

Watch video on how to use diamond pad on potter's wheel by clicking button below.
Video: Diamond Pad for Potter's Wheel
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STONE GRINDING BIT FOR DREMEL
Purpose: to grind off partially fused wads.

​Watch video on how to use stone grinding bit for dremel by clicking button below.
Video: Stone Grinding Bit
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WET SANDPAPER AND/OR DIAMOND PADS
​Purpose: to give a smoother texture to pots.

​Watch video on how to use wet sandpaper and hand diamond pads by clicking buttons below.
Video: Wet Sandpaper
Video: Diamond Pads
Read more articles to learn more about soda firing by clicking button on right.
More Soda Firing Articles
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Soda versus Salt Firing

7/17/2019

 

What color saturation do you like?

Soda = Brighter Colors
Salt = Muted Colors
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Vessels, Heavy Soda/Reduction in a Gas Firing
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Vessel, Wood Fired in a Salt Chamber
Orange Peel surface texture can happen in both soda and salt firings. If you desire to obtain orange peel surfaces select a clay body that contains a lot of silica sand, or add additional silica sand.
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Soda Fired Mug with Yellow Salt Glaze on White Stoneware.
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Soda Fired Creamer and Mug with Yellow Salt Glaze on White Stoneware.


​I really enjoy opportunities to fire in both Soda and Salt kilns.
 For the majority of my work I choose to fire in soda as I appreciate the brighter color palette. While some glazes cooperate in both soda and salt firing not all recipes are interchangeable in the success of how they come out of each unique kiln. So it's important to test your glazes and slips. Note which ones you like best in which firing atmosphere.

​Read more articles to learn more about soda firing by clicking button below.
Learn More
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Wood Fired Bud Vase in Salt Chamber
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Interview: Kristen Kieffer

7/1/2019

 

Artists Who Used to Soda Fire

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Left: Soda Fired Jar 2005 Right: Electric Fired Jar 2007
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Soda Fired Flower Brick 2005
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Top: Soda Fired Mugs 2005 Bottom: Electric Fired Mugs 2007
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​About Kristen: Full-time studio potter since 2003.
 

What attracted you to soda firing?
"I began soda-firing when I worked with studio potter John Glick at his studio in MI in 1996-97. As a ‘precise potter,’ I liked the variation in surface it provided, and the beautiful depth."
 

What led you to leaving soda firing?

"Buying a house in 2005, and not being able to afford to build a kiln, nor having one in proximity. If I hadn’t have HAD to abandon soda, I probably would have plugged on, but it was the best thing that could happen to me and my work. I love color, and cone 10 soda reduction is automatically going to result in duller, bleached-out color. Switching to cone 7 oxidation gave me COLOR!"
 

What aspects do you miss and not miss about soda firing?
"I miss some of the colors available from soda (flashing oranges, for example), but that’s about it.
I don’t miss wadding;  filling and loading a larger kiln;  the duty (time & attention) required in firing a gas kiln;  wearing eye protection and respirator to spray soda;  problems with the sprayer;  bricking up the door;  problems with the kiln;  anxiety of firing with gas;  drummeling glaze drips and wadding;  crap falling into work during the firing and being glazed in place;  scraping and washing shelves;  bad results; limitation on forms;  and lastly, customers not understanding the variation.  So apparently I don’t miss it much."
 
​
What aspects of soda firing do you reference in your current work?
"I’m not sure." Read post on use of layers by clicking here.
Images above are examples of Kristen's current work, check out her more of her work on her website.

Read more articles to learn more about soda firing by clicking button on right.
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1. Soda Fire Artist: Tim Sherman

6/13/2019

 

Anagama Soda Kiln

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About Tim:
"I make functional, utilitarian pottery in an anagama style wood-burning kiln."

Why did you decide to build an anagama kiln?
"
After firing many types of kilns and seeing a wide range of surfaces, I decided that an anagama produces the types of effects and colors that interested me most. I also wanted a kiln big enough to fire large pots and would also have room to fire work from other potters that would make up a firing crew."
 
Why do you put soda just in the back of your anagama kiln?
"While firing with Andrew Snyder in his groundhog kiln, he explained that he introduced soda into the back of his kiln to help liven up areas that usually yielded dry pots. Because the draught in an anagama is one directional with the flame always moving toward the chimney, I saw this practice as a way to get a wide verity of surfaces in just one firing. Pots in the front have very traditional ash covered surfaces while the pots near the stack often have very colorful, textured surfaces."
 
What is your favorite part about the mix of soda and wood firing?
"It’s like having two completely unique kilns that only require the labor and fuel of one."
 
How do you put soda into your kiln?
"I make a thick slurry and spread it on long, wide boards and stoke it in between cycles."
 
When do you put soda into your kiln?
"When cone 10 is touching the cone pack in the very back of the kiln."
 
What glazes, clays, and slips work best for your soda firing?
"Both porcelain and stoneware clays work very will in the back of the kiln. I put all types of slips and glazes in the soda section as well, but recipes that are high in silica seem to attract more soda and carbon trapping than ones than don’t."
A Favorite Cone 10 Glaze Recipe:
Val’s White:
(can be easily colored by adding 1-2% of most any oxide)
Cornwall Stone 46
Silica 20
Whiting 34
A Favorite Cone 10 Slip Recipe:
Bauer Flashing Slip:
(Must be applied very thin. I use a spray gun.)
EPK 41.9
Ball Clay 41.9
Borax 5.7
Zircopax 10.5
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​
Find Tim on: 
Instagram @shermanceramics
Shermanceramics.com

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Interview: Deborah Schwartzkopf

6/12/2019

 

Artists Who Used to Soda Fire

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PHOTO by Takashi Fukuda

​About Deb:
"Seattle based studio potter and instructor at Rat City Studios, where I offer classes, studio assistant positions, workshops, and host community events."
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Color grouping from 2007 - Salt fired, Cone 10 Oxidation Gas Kiln
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Place Setting Brown from 2015 - Cone 6 Electric Fired
What attracted you to soda and salt firing?
"Seeing other people’s results. I wanted the variation that the introduction of soda offered.  I was still learning to use glaze and this felt like the kiln was on my side!  I also enjoyed having more interaction with the firing process. I fired oxidation so I was constantly adjusting to keep the kilns from reducing and adding salt or soda at the end felt like a finale. "
 
What aspects do you miss and not miss about soda firing?
"I do not miss much... The kilns I had access to were challenging to keep in oxidation and keep even.  And the soda would often remove glazing decisions that I made and wanted…  The kilns I had access to were quite old and would spald off bits of debris…  I do not miss that.

I miss firing the kiln. (pushing the start button is nice, but much less interaction). I miss having a large kiln to fill.  I miss the interaction of sharing a large kiln.  And I miss wadding pots and group loadings.

I just got a bunch of brick from an old gas kiln.  So in a year or two I may be building a new soda kiln!"
 
What aspects of soda firing do you reference in your current work?
"I have chosen to fire cone 6 electric.  This shift to a lower temp happened when I got my own studio.  Installing an electric kiln was much easier in a smaller private city space than a gas kiln.  And much more affordable.  Now I love it!

I spray layers of glaze to create the variation I enjoy.  Initially I sprayed a soda ash solution.  Then moved on to a more fluxed out glaze…  Like a clear.  Now I use lots of different glazes. I spray a whole ware board of pots at a time…" Click here to read more about this process.
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2018, Pitcher Cone 6 Electric

​Any recommendations on how to transition from soda firing to electric firing?
"Glaze test like crazy!  Use test tiles that are made in a similar fashion to your working process.  Make medium to large test tiles so you have space to capture variation from spraying."

For Deb shares a lot of resources on her website. Click on each topic to learn more: Glaze Recipes Resource and Surface Techniques Resource.
Learn more about deb on: Instagram: @debspottery and @ratcitystudios, Youtube and her website.
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Rat City Studios
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Rat City Kiln Yard
All Photo credit belongs to Deborah Schwartzkopf 
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