Hamish Jackson Hamish Jackson

NCECA In Review: Portland 2017. Concurrent Wood Firing Exhibitions: Ashes & Flux and Great Waves Over the Pacific.

These two wood firing exhibitions were held concurrently in the Chehalem Cultural Centre in Newberg, Oregon. Wood-fired pottery is what I am practicing and love, so I was especially excited to see these shows. The Chehalem Centre was a bit of a drive outside Portland, but we hooked up with some old friends and ate at a fantastic Korean market on the way.

In the interest of good record-keeping, I have written out the labels on the pieces as they were in the exhibitions, including their prices. I've also included links to the artists' websites where I could find them.

Great Waves Over the Pacific: On Wood Firing. (March 7 - March 25, 2017)

This exhibition focused on the influence of the artist Takashi Nakazato's influence on Japanese and American ceramics. Nakazato travelled widely around the Pacific learning and sharing methods of making. Takashi was born into a pottery family. His father was the twelfth in line of a long line of masters in the Nakazato family. They are the most eminent family in Karatsu, whose name has become synonymous with pottery. 

Takashi has pushed the traditions of his family, creating ceramics with a new vitality; he uses the term 'Karatsu Nanban' to describe his style. 'Nanban' refers to unglazed pottery which had long been made in other parts of Asia, such as Southern China, but never Japan until the sixteenth century. His influence in America has been in aiding the spread of wood firing unglazed work, especially in anagama kilns. The artist Ruri organised this show around these principals. Ruri fired the FuuKooGama, which she owns and operates, before the conference started with guest artists John Neely, Doug Casebeer and Chris Gustin. Wish I could have come out to see it in action!

I did not photograph every piece (should have in retrospect) but here is a smattering...

View from afar.


Flow, Ruri. Anagama fired stoneware. $900.


Vase #1705, Chris Gustin. Stoneware. $4200. 


Vase #1704Chris Gustin. Stoneware. $3800.


Close-up of the above piece. I love the soft satin surface of these pots.


Just Like a Drop of Rain, Ruri. Anagama fired stoneware. $1900.


Buena Vista Vase, Brad McLemore. Ceramics. $95.


Tea Bowl 2, John Neely. Wood-fired stoneware. $400.



Kaiseki for Two, Collaboration between Takeshi Nakazato, Fumiko Nagai and Ruri. Wood fired stoneware.


Small plate with wadding pattern, Fumiko Nagai, and Chop stick stands by Ruri.


Close up of Nagai's small plate with wadding pattern.


Square Platter, Brad McLemore. $175. 


Bardo, Ruri. Anagama fired stoneware. $900.


Considering Ruri's hanging sculpture. Photo credit: Brad Yazzolino


Gustin's gourd and I, getting intimate. Photo credit: Brad Yazzolino

Ashes & Flux. (March 7th - 25, 2017)

This exhibition was in the same gallery space as the Great Waves show, and the transition was easy. Ashes & Flux represents the wood-fired pottery of the North West. It concentrated on the work coming out of four anagama stye kilns: East Creek, Noble Hill, Pleasant Hill, and the FuuKooGama. 




The four kilns represented with a bit of info on each.


Central to this blossoming tradition is the East Creek Anagama. This was the first anagama kiln built in the U.S. west of the Mississippi. The project was started by Nils Lou, Frank Boydon, and Tom Coleman approximately 32 years ago. It was based on an eighth century Korean kiln. Made of over 5,000 hand cut bricks, it measures about 16 feet long, 6 wide, and 5 tall. Many students have come to help prepare for firings and take shifts firing the kiln. It was East Creek that spawned the other three anagama kilns included in this exhibition. I'll show the pots from East Creek first though.

Red Barron Flying Ace, Andrew Butterfield. East Creek. $80.


In front: Gourd 3, Lori Allen. East Creek. $350.
Behind: Funky Bottle, Lew Allen. East Creek. NFS.


Sculpture #2, Don Haskisson. East Creek. $320.


Whiskey Bottle with Tomobako, Joe Robinson. East Creek. $195.


Hammered Jar, Lew Allen. East Creek. $120.


The Better to Smell You With, Andrew Butterfield. East Creek. $75.


Cut of the Same Cloth, Mya Haskisson. East Creek. $200.


Cut of the Same Cloth, Mya Haskisson. East Creek. $200.


Steeler, Mike Helle. East Creek. $450.
I love this fish.


Steeler, Mike Helle. East Creek. $450.


Jar with Lugs, Joe Robinson. East Creek. $975.


Gourd 2, Lori Allen. East Creek. $350.


40lb Jar, Joe Robinson. East Creek. $1850.



Completed in 2004, the Noble Hill anagama was built (on a Christmas Tree farm) by Mark Terry. He was inspired to build his own anagama by years of firing at East Creek. It is only about 120 cubic feet (about a third of the size of East Creek's kiln). In its 13 years of use, Terry's kiln has been fired more than 60 times and served to introduce many young potters to wood firing.

Ariadne, Mark Terry. Noble Hill. $2800.


Bottle, Amy Burnham. Noble Hill. NFS.


Bottles, Amy LeFever. Noble Hill. NFS.


Drip Vase, Jim Busby. Noble Hill. NFS.


Drip Vase, Jim Busby. Noble Hill. NFS.


Whiskey Vase, Amy Burnham. Noble Hill. NFS.


Stoneware Teapot, Burk Kielber. Noble Hill. $350.


Stoneware Teapot, Burk Kielber. Noble Hill. $375.


Jar, Jim Busby. Noble Hill. NFS.


The FuuKooGama was designed, owned and operated by Ruri. It was modified/built with help from Yoshiyuki Ito, Mashiko. The main aim was to vitrify the pots without any slip or glaze or really any form of surface manipulation. FuuKooGama means "Wind and Light Kiln" (Foo means wind and Koo means light). She describes in her video interview (linked below) that often you cannot see wind or light, but can feel it: Ruri tries to express something she cannot see through clay that is transformed in her kiln. This definitely ties in to Takashi Nakazato's teaching. As well as the below pictures, all of Ruri's work on display in the Waves exhibition was anagama fired for seven days in the FuuKooGama.

There is a great video on youtube about Ruri and her work, especially discussing building and firing the FuuKooGama. This is part 1 of 2: https://www.youtube.com/watch?v=ub8FUqj5lgY

I particularly enjoyed how she talks about the flame in the kiln moving like a mountain stream; speeding up where pieces are closely packed and causing flashing effects.

Woodfired Vases, Kimberly Ota, FuuKooGama. NFS. (The centre and right vases).
Long-necked Vase, Nathan Paddock, FuuKooGama.

Large Bottle, Brad McLemore. FuuKooGama. $200.


Conversation II (Diptych), Ruri & Brad McLemore. FuuKooGama. $200.


Some of my favorite pots from Ashes & Flux came out of Pleasant Hill. It was started in 2000 by Tom Rohr and Kathryn Finnerty, but has since been taken over by Jesse Jones and Lauren Sommers. They have four wood kilns now. The first was built in 2001; a 60 cubic foot two-chambered wood, biodiesel, salt kiln-named 'Pepino.' Next came a 110 cubic foot anagama, named 'Tomogama,' in 2007. Then they added a wood/biodiesel soda kiln in 2014 and finally a small wood/biodiesel train kiln was built in 2014.
Pitcher, Spencer Dixon. Pleasant Hill. $250. (Fired in the train kiln).


Pitcher, Spencer Dixon. Pleasant Hill. $250.


Wall Hanging Plates, Jesse Jones, Pleasant Hill, $450/set. Anagama fired.


Wall Hanging Plates, Jesse Jones, Pleasant Hill, $450/set. Anagama fired.


Wall Hanging Plates, Jesse Jones, Pleasant Hill, $450/set. Anagama fired.


Wall Hanging Plates, Jesse Jones, Pleasant Hill, $450/set. Anagama fired.


As you can tell, I liked these plates a lot. Amazing silky flashed surfaces. Jesse told me that the plates were unglazed and unslipped going in the kiln; made using a g-mix... a clay mixed by a local company called Georgies. They were fired in the anagama close to the floor, about 18" off the face, in a stack of four with about an inch in between each plate.

Wall Hanging Plates, Jesse Jones, Pleasant Hill, $450/set. Anagama fired.


Vase, Richard Brandt. Pleasant Hill. $450. Anagama fired.


Gongfu Cha Set, Jonathan Steele. Pleasant Hill. $200.


Cast Solo Cups, Jesse Jones. Pleasant Hill. Anagama fired.


Sipping Set, Barb Campbell. Pleasant Hill. $300. Anagama fired.


Trio of Vase, Barb Campbell. Pleasant Hill. $400. Anagama fired.


Jar with Bronze Lid, James Tingey. Pleasant Hill. $600. Anagama fired.


Lauren and her mum enjoying the exhibit. Photo credit: Brad Yazzolino


This exhibition reminded me how large wood kilns such as these can bring people together and foster learning experiences outside of formal college environs. I think it could be an interesting model to consider when I build a kiln of my own. Having additional people to help prepare all the wood, grind the kiln shelves, load, and fire must be pretty nice too!

Well I think that's all for now. Wish we had had time to go out and visit these kilns. Next time!

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NCECA In Review: Portland 2017. National Student Juried Exhibition, OCAC.

It was about 8:58pm when we made it to the Oregon College of Art and Craft. The gallery closed at 9pm. A late dinner had postponed our arrival somewhat. But the lady in charge was very nice and let us in to see the show for as long as we liked. The pieces sat well in the newly renovated gallery at OCAC.

Being in the gallery after hours, on the night of the reception, there was a kind of leftover electricity in the air. The feeling that hundreds of people had already traipsed through and had their fill. Despite the lack of functional work, I enjoyed the show; the choices were whimsical. I particularly enjoyed Kaysner's cow, with weeping feldspatic chunks, and Pasquale's utterly squashed donut.

I have not included all of the pieces in the show, but most of them, with links to the artists websites where available.

Black Holstein Shigaraki, Elliot Kaysner, 2016. 
Terracotta, underglaze, felspathic chunks. Graduate, Arizona State University.



Regretting Yet Wanting, Taylor Pasquale, 2016.
Ceramic materials, ceramic plate, donut. Graduate, Kent State University.


I was curious about the lifespan of the donut. Pasquale told me she does not treat it with anything, replacing the donut if it's part of a new show or she's taking photos. She says, "The donut looks so good when the glaze is still wet and drippy, but the reception didn't line up with that part of the piece's life cycle."

I had most fun with Kingshill's Dream Truck. Coming upon it, I gave in to the urge to pick it up. In doing so, I realised it came apart -- the surfboard was completely unattached and the whole cab was removable, too. Surprised and delighted I took the cab off and placed the board in the flatbed of the truck. That was about as far as it went; I was tempted to take it off the pedestal, onto the floor, but resisted.


Dream Truck, Patrick Kingshill, 2016. 
Ceramic. Graduate, University of Nebraska-Lincoln.


I emailed a bit with Patrick Kingshill and he said that Dream Truck represents a departure from his normal practice of making functional vessels. He is an 'obsessive doodler' who grew up in Eureka on the coast of Northern California and has surfed since he was 14. The downside to getting a grad degree in Nebraska = it's very far from the surf. This latent desire really came out in this three-dimensional doodle.

Dream Truck, Patrick Kingshill, 2016. 
Ceramic. Graduate, University of Nebraska-Lincoln.


No one saw as I gingerly put it back together.

I did not touch Franco's Golden. In fact, I felt rather awkward examining and taking pictures of her golden behind. Imagine applying that lustre in the studio. 

Golden, Lorraine Franco, 2016. 
Ceramics. Undergraduate, University of Miami.


Golden, Lorraine Franco, 2016. 
Ceramics. Undergraduate, University of Miami.


I have to admit that some pieces fell flat in my eyes; Bevington's It's okay... I'm okay was simply silly, and I did not find much significance in Jeong's Want to Value


It's okay... I'm okay. Ashley Bevington, 2016. 
Clay, glaze, wood, mirror, paint. Graduate, Edinboro University of Pennsylvania.



Want to Value, Kwan Jeong, 2016. 
Porcelain, underglaze, low firing glaze. Graduate, Syracuse University.


Overall, I was left wanting more pots. There were only four representatives of functional ceramics in the exhibition. When I got to McDaniel's Sunshine Mug I had this sense of deja vu because, as I realised later, it had been featured in the NCECA Program guide. It made me laugh at the time though... to have a simple, yet well-made, mug sat right next to Fahley's deconstructed horse. It felt totally incongruous... as if someone in charge had been like "oh shit, we need a cup in the show." 

Sunshine Mug, Caelin McDaniel, 2016. 
Stoneware. Undergraduate, Edinboro University of Pennysylvania.


Survived by:, Shauna Fahley, 2016. 
Ceramic, wood, resin. Undergraduate, University of Washington.


Stuart Gair's tea set also felt out of place, as if stranded on a life-raft in a choppy sea of ardently Parisian coffee drinkers. 



Large jar, teapot and teabowlStuart Gair, 2016. 

Soda fired stoneware. Graduate, University of Nebraska-Lincoln.


I thought the other two functional pieces were thoughtfully placed, though: Tang's porcelain jar stood out, with its bright shiny porcelain surface and obsessive blue dots, complemented by Deroualle's soft panels nearby. 

Individuality, Tiffany Tang, 2016. 
Porcelain. Graduate, University of Montana.


Untitled, Louise Deroualle, 2016. 
Ceramic. University of Nebraska, Lincoln.

Close ups...

Individuality, Tiffany Tang, 2016. 

Porcelain. Graduate, University of Montana.


Untitled, Louise Deroualle, 2016. 
Ceramic. University of Nebraska, Lincoln.


And I chuckled at the ironic placement of Kellner's earthenware Meat Tray underneath Larrabee's skeletal Companions. 

Companions, Teresa Larrabee, 2016. 
Stoneware, underglaze, mixed media. Post-baccalaureate, University of North Texas.


Meat Tray, Andrew Kellner, 2016. 
Earthenware. Graduate, West Virginia University.


I thought, to begin, that the show's main collision was between 'art' and 'craft.' But then, it is not that simple -- many of the sculptures, such as Wilson's Foul Fowl and Calhoun's Self-Image, are finely crafted, and Tang's piece could be seen as Art with a capital A. Perhaps a better way to describe the collision is between the 'conceptual art piece' and the 'functional pot.' This is the great dichotomy of the current ceramic art world, especially that of university programs. Students seem to be pushed to conceptualise first and make second. 

Foul Fowl, Mary Cale Wilson, 2016. 
Earthenware. Graduate, San Diego State University.


Self Image, Liam Calhoun, 2016.  
Raku fired ceramic. Undergraduate, Buffalo State College.


To my mind, there is something inherently special about a well-conceived and executed functional pot; the possibility of its use imbues it with some sort of magic. But this magic was present in Kingshill's Truck, too. I wanted to take it apart and play with it. And that is not to say I value function over all else, but it certainly informs my aesthetic inclination. Would I enjoy Cinelli's Reliquary for Boredom more if it 1) were an open vessel 2) did not have a brain hovering over it and 3) did not have a fancy title? Possibly. Why? I don't know. Maybe because I am a peasant potter at heart.



Reliquary for Boredom, Mike Cinelli, 2016. 
Earthenware, commercial underglaze, terra sigilata. Post-baccalaureate, University of Mississippi.

There's more under the surface of my present thoughts, bugging me. Take Ballard's Brave, for instance. What does a peasant potter do with that? It's earthenware, sure, but with nail polish?

Brave, Rachel Ballard, 2016. 
Earthenware glaze, micro-crystalline glaze, nail polish. Graduate, Georgia State University.


I don't know. I'm confused. That's NCECA. Maybe that's the point. Maybe it's fine. I should probably let go and embrace the collisions. Here's a last couple of pieces with fantastic surface and texture.

Blue Velvet Water, Sarah Heitmeyer, 2016. 
Slip cast porcelain, glaze. Graduate, SUNY New Paltz.


Squares on Squares on Square, 2016, Yewen Dong
Ceramic. Graduate, School of Art Institute of Chicago.


Squares on Squares on Square, 2016, Yewen Dong
Ceramic. Graduate, School of Art Institute of Chicago.


I can't help feeling that we should have separate exhibitions for students' functional and conceptual pieces, but the clash of them can indeed be compelling. Perhaps I just want a fairer representation of the excellent functional pots being made out there. I want them to be prominent and not feel like afterthoughts. Here is my afterthought for now... LeFever's untitled wall sculpture. It was made originally with a 3D printer and then slip cast from that. The world's a changing.


Untitled, Amy LeFever, 2016. 
Slip cast earthenware from 3D printed model, designed in Rhino software program. Graduate, University of Tennessee, Knoxville.


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Mark Hewitt: Ginger Jar Production. Spring, 2017.

I was invited by the Boston-based Pucker Gallery to do a take-over of their Instagram account a couple of weeks ago. The Pucker Gallery represents my mentor and boss Mark Hewitt, and they are currently having an exhibition of his work. 

Generally I don't get the opportunity to take a lot of snaps at work, since I'm busy with other tasks and my own pots. I thought it would be nice to share some of the pictures that I posted for Pucker with some of the nearly-made-its. They follow Mark's ginger jars throughout the week. There are a few pictures to provide context, and some videos, too. I appreciated having the chance to record Mark's process a bit more, too.
Good morning from the Hewitt Pottery! Mark is in full flow churning out ginger jars this morning. He started with 18 little 1 1/2lb bodies and is on to 2 1/4lb ones now. This one is about to come off the wheel. Larger ginger jars to follow after lunch. This is the first post of this weeks insta take over by me @hamramics by the way.


Last board of the day-board number 6-slides into the drying rack. Now Mr Hewitt is going to get on with making lids and I'm heading home. More pics to follow tomorrow! 


The potters hands! Mark finishing up his batch of lids this morning. He'll get them out in the sun to dry and add the knobs this afternoon.


Mark trimming up the lids for his ginger jars and adding knobs. Only 40 more to go! 


How do you know it's a Mark Hewitt? The stamp on the right is Mark's monogram. W.M.H all rolled into one. The 'elle' refers to the firing... we go numerically in the salt kiln and alphabetically in the newer wood kiln. Elle = L so this will be the twelfth firing of the kiln.


Mark trimming up the lids for his ginger jars and adding knobs. Only 40 more to go! 


Trimmed up lid with its freshly thrown knob. Two expectant ginger jars in the background. Happy women's day!


Some of Mark ginger jars about to be put under plastic to await decoration on Friday. He's flying along making larger 5lb and 8lb jars today, whilst @stillyv (my fellow apprentice) and I clean and wash kiln furniture.


Stillman weighing out some balls of clay for himself.


Mark throwing larger ginger jars later in the week-8lb ones.


The look much larger in real life.


The master at work, from above.


8lb jar from the side.


Here's a view from across the pond. Mark's house in the front, the barn which we use as a gallery at the kiln openings in the back and the solar panels that power the property on the right. The workshop and kiln are obscured from this angle but I'll get there later. This is @hamramics reporting from the Hewitt Pottery.


View from the roof of the kiln shed.



We ran out of space for pots in the workshop so have had to store some in the back chamber of Mark's newer wood kiln. His mugs up front and some of my teapots etc behind.


This is the salt kiln that Mark built in his first year in Pittsboro (1983). It has seen 96 firings so far and shows no signs of falling apart yet. Touch wood. The design was based on Thai climbing kilns and came together with the help of Svend Bayer. The kiln fits so many pots it takes us a full week to load. We light the fire (generally) on a Wednesday afternoon and finish firing on Saturday afternoon. It's an epic and crucial endeavor-4 months worth of work all inside one kiln. Once fired we wait a week for it to cool and then get to crack it open and see how they came out.



I think this is the heart of the Hewitt Pottery: the dirt floor of the workshop. It is gnobbled and gnarled from years of potters' feet walking to and fro. The bumps are hardened like polished river stones and can easily put you off balance if you take a wrong step. Carrying boards of pots felt dangerous when I begun my apprenticeship, just as I'm sure actors quiver as they "tread the boards" for the first time on the main stage. 

When people arrive, they always react to it; once a group of kids from a school for the blind visited and were excited to find such a bumpy landscape in the studio. Mark calls it his air conditioning unit as it helps keep the workshop cool in the summer (perhaps cool is an overstatement). My favorite feature is its ability to absorb all sorts of spills; splashes of water or glaze or clay disappear underfoot. We have to sweep very infrequently, and when we do it is with the romantic sense and dusty scent of being a potter sweeping a dirt floor. I could go on, but will spare you. I say tear up your concrete floors and go back to bare earth! 



End of the day. Mark working on lids, Stillman watching, barefoot as usual!


Mark decorating one of his fat 5lb ginger jars this afternoon. Red slip banding with white slip swirls. Mark is working on the treadle wheel that he built when he first started the pottery. 


Closer angle - different pot but same idea!


Freshly trailed jars.



Mark switching between the treadle wheel and one of our electric wheels.


I asked Mark to give me his best Ai Weiwei pose. Here it is. You'll be glad to know he didn't actually drop the jar.


This is the final post of my Pucker Gallery takeover. It's been a fun week sharing pictures from the pottery. I thought it fitting to end on a pic of the current team... Mark (@wmhewitt) on the right, me in the middle (@hamramics) and my fellow (barefoot) apprentice Stillman Browning-Howe (@stillyv) on the left. Thank you @puckergallery for inviting me to do this!
...

Now I really need to pack as we leave for NCECA in Portland tomorrow and it's late and I am horribly unprepared. First task: find my waterproofs.
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All About Ceramics Crazing: Why Glazes Craze And How To Avoid Crazing


At the Hewitt Pottery we have been developing some glazes using local granites with a high felspatic content. The glazes are beautiful and sparkly but we have experienced some issues with crazing, so during our recent snowstorm, I spent some time reading through books and looking online to see what I could glean. I wanted to share the sum of what I have learned here in three sections: 1) Why is crazing a concern?, 2) Why causes crazing?, and, 3) What can we do to eliminate crazing?

1) Why is crazing a concern? 

Crazing can be an attractive feature of a pot and is often called "crackle" when intentionally used, such as on this tea bowl:

Intentional crazing, or "white crackle" glaze, on a tea bowl by Richard Brandt.

There are reasons why crazing is not ideal for functional pottery, however. Crazed pots may leak if the clay body is not totally vitrified, and potentially be unsanitary as bacteria can grow in the cracks. Structurally, crazing is also an issue as Michael Cardew points out in Pioneer Pottery, (p. 84), "It has been proved that glaze fit has a major effect on strength."

Cardew describes an experiment (recorded by Bettany and Webb in the British Ceramic Society's publication Transactions. Vol 40, p. 316), in which rods of porcelain are treated three different ways: some are left unglazed, some are dipped in a crazing glaze, and some in a sound glaze. The results after firing showed the comparative strengths of the rods in the proportions 40 : 100 : 160 (crazed : unglazed : sound). The results indicate that "vitreous ware with a non-crazing glaze may be three to four times stronger than ware which is crazed." Furthermore, a properly glazed pot will have a greater resistance to thermal shock. As a potter engaged in producing functional pottery, strength and resistance to thermal shock are important qualities, especially when one considers the competition of industrially produced wares.

The ideal, as Daniel Rhodes puts it in Clay and Glazes for the Potter (p. 255), for maximum durability and fit, "a glaze should be in slight compression over the body." See the kitten sweater below... it should be just a little bit snug for optimal cuteness.

This is Mango (not our cat, unfortunately).


2) What causes crazing?

John Colbeck (Pottery Materials, p. 61) says, "Crazing occurs when, on cooling, a body does not shrink more than the glaze." In other words, the glaze shrinks more than the body. It's as if Mango the kitten jumped into a tumble drier wearing her knitted sweater; the sweater would likely shrink more than her body and it would be quite a squeeze. This analogy doesn't totally work... but I wanted to include a picture of a cat in a sweater.

If you have a glaze that shrinks less than the clay body, then you can experience shivering, although this is more rare than crazing. {Side note from Michael Cardew on the difference between these defects: "It is always easy to tell the difference between shivering and crazing. Sometimes mild shivering may look like crazing, but the cracks are not on the surface of the glaze only; they can be seen right through the body" (p. 86).}

Crazing is not related to the shrinkage rate of the clay. As Rhodes points out (p. 255), all of the shrinkage happens when the wares are heating up. During the firing, whilst the pots are red hot and the glazes are still wet and molten, they fit the pots perfectly. It is upon the cooling of the kiln and the contraction of the wares that cracks form. The key point is that "some materials expand more when heated, and therefore contract more when cooling." This is called the coefficient of expansion. He goes on to say, "The cause of crazing, then, is always to be found in a high coefficient of expansion (and therefore contraction) in the glaze relative to the expansion of the body." I have copied out Rhodes' list (from English and Turner) of the expansion coefficients of some common materials used in ceramics:


SiO2          .05
Al2O3        .07
B2O3          .66
Na2O          4.32
K2O            3.90
PbO           1.06
ZnO           .07
CaO           1.63
MgO           .45
BaO           1.73


We can see from this list that oxides vary wildly in their coefficients of expansion: "Silica expands less than one eighteenth as much as sodium. Clay, being made up of alumina and silica, has a medium expansion; but some glazes, especially those high in soda, may have a high expansion" (p.255). So it's clear that your clay body and glazes will vary in their coefficients of expansion depending on the differing oxides present in them. Going into the science of this a bit deeper, we arrive at the formation of a substance called cristobalite. 


A Bit About Cristobalite:

John Colbeck explains (p. 62):

  • "Crazing needs to be considered in relation to clay bodies as well as glazes. The important factor to remember here is the role of cristobalite. Cristobalite, a crystalline form of silica, undergoes a contraction about 22°C (far below the temperature where glazes are molten). Cristobalite is formed quite slowly, at temperatures above 1,020°C, from the free silica which exists in bodies. It is not found in glazes because the free silica, whether high or low, react with fluxes to form the glaze solution. Thus bodies in which cristobalite has developed contract at 220°C as they cool, where glazes do not. It is this contraction of bodies which helps in the prevention of crazing by putting the cooling glaze under compression. Thus to diminish the tendency of a glaze to craze, any steps which assist the formation of cristobalite."

This leads nicely on to the important bit -- how to adapt glazes to reduce or eliminate crazing.

Two of my mugs from firing 96 at the Hewitt Pottery. If you look closely, you can see the crazing.


3) What can we do to eliminate crazing? 

Adapting your clay body:

Conventional wisdom suggests that adding silica to your clay body is the first port of call. Cardew says you can increase silica in either body or glaze, but that it tends to be more effective in the body.

Colbeck says you can assist the formation of cristobalite by adding silica to the body because this "will increase the free silica in it which is available to form cristobalite" (p. 62).

Rhodes agrees but warns, "bodies that contain more than about 25% of silica may be hard to fire without dunting or cracking." Conversely, bodies with "less than about 10% of silica... may be expected to be difficult to fit with glazes" (p. 256). There is clearly a sweet spot to be found with the amount of silica, and subsequently cristobalite, in your clay body. In A Potter's Book, Bernard Leach recommends 5-15% cristobalite in a body. He says this is enough to produce the cristobalite squeeze, "which exerts a centripetal compression on a glaze which tends to prevent crazing" (p.176). He notes that cristobalite can be cheaply acquired as powdered silica-brick waste.

Leach goes on, "the addition of powdered flint is usually the first alteration to a body to prevent crazing, but more important than an increase in quantity is a decrease in the particle size of silica." This is something that none of my other sources mentioned, but it is worth considering. He also mentions the option of increasing the cristobalite content using talc as "it acts as a catalyst and assists the transformation of silica" (p. 176). He also makes a distinction over vitrification; "in non-vitrified bodies the amount of flux should be increased and in non-vitrified bodies the reverse is true. Finally, in bodies which contain ball clay and china clay, the former should be increased, the latter decreased" (p. 177).

This advice is all well and good if you have the option of changing your clay body easily and testing it extensively, but many potters do not have this luxury. Changing the formulation of the glaze may be an easier option, or the only option.


Adapting your glaze:

The aim here is to reduce the coefficient of expansion of the glaze (to stop it contracting as much on cooling). This means adding oxides with low coefficients of expansion and decreasing some of the materials with higher coefficients of expansion. As Rhodes points out, this can be tricky "without altering the maturing temperature or appearance of the glaze" (p. 255). He recommends:

      1) increasing the silica
      2) decreasing the feldspar
      3) decreasing materials containing potash/soda
      4) increasing the boric oxide
      5) increasing the alumina

Leach also recommends increasing the silica content and possibly borax or raw boracalite (B2O3), and/or decreasing the alkaline content of the glaze.

Thinning down the glaze may also help reduce or eliminate crazing; as Colbeck says "thick layers of glaze are always more prone to crazing than thin" (p.62).

The website/database Digital Fire has some excellent articles on the subject. It recommends decreasing the potassium oxides and sodium oxides present in your glazes: these are typically found in potash feldspar, soda feldspars, nepheline syenite and frits. The issue with reducing your these is that the glaze may be less inclined to melt, so then you have to add some more flux and these adjustments may alter the look of the glaze. Digital Fire also recommends increasing your magnesium oxide. Talc and dolomite are excellent sources of MgO and purportedly effective at high temperatures, (for cone 6 you may want to use frits like Fusion F69 or Ferro 3249). They show one test where an addition of 10% talc helped eradicate crazing.

One of my teapots from Firing 96 at the Hewitt Pottery. The crazing is particularly obvious where the glaze is thick around the lid.


Final notes: 

You can tell how much your glaze does not fit your body by looking at the cracks: a network of lots of small cracks means you have greater stress than a few larger cracks. It is easier to fix the latter as you might expect.

Rhodes also posits that over firing can cause crazing, "if the firing has proceeded to the point where the free silica in the body has entered into glassy melts with the other materials, it does not go through any crystalline change upon cooling and so does not lose volume and put the glaze into compression" (p. 256).

Another issue can be removing pots from the kiln whilst they are still too hot: the kiln must be under 200°C. The heat shock of opening the kiln too soon or even putting wares atop of an oven/stove can induce crazing.

This post has been about primary crazing, but there is also such a thing as secondary crazing. This can happen with bodies which are not fully vitrified. Colbeck says porous bodies can "subsequently absorb water, causing the body to expand fractionally" (p. 62) which can craze a previously uncrazed glaze, months or even years after coming out of the kiln.

I don't want to end on a downer, but Daniel Rhodes does say that in glazes with a high content of "soda or potash in the form of feldspars, frits or raw alkalines," it may be "impossible to correct crazing without completely altering the character of the glaze" (p. 255). Our celadon glazes do contain a very high proportion of feldspar so the exercise could be tricky. It is worth a shot though -- especially if you have the ability to adjust your clay body as we do. I plan to test various methods and see what works best.



I hope some of this was helpful. Like a wise karate master from the movies, I leave you with these simple words...


Glaze on. Craze off. Glaze on. Craze off. Glaze on. Craze off. 





Works Cited


Cardew, Michael. Pioneer Pottery. London: A. & C. Black, 2002. 
Colbeck, John. Pottery Materials: Their Composition, Preparation and Use. London: Batsford, 1988.
Leach, Bernard. A Potter's Book. London: Faber and Faber, 1945. 
Rhodes, Daniel. Clay and Glazes for the Potter. Third ed. N.p.: Krause Publications, 2000. 



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Firing 96, Mark Hewitt Pottery. Firing and Kiln Opening.

It was an unusually mild but blustery morning when I arrived at the kiln at 5.30am. Stillman and his brother Leavitt had taken the night shift, which ran from midnight until then. Their job was to maintain a reducing atmosphere in the kiln and not worry too much about heat gain: by limiting the amount of air entering the kiln, oxygen is pulled out of the pots and glaze materials. There still needs to be enough oxygen for the wood to burn, though, so it's a tricky balance of blocking the kiln up whilst not letting it stall out. Reduction tends to make for nice deep colors rather than pasty ones.

Daybreak at the pottery

When I arrived the pyrometer read about 2100°F. Black smoke emanating from the chimney and piles of ashes halfway down the kiln suggested that the boys had done a good job. Side stoking helps to keep the reduction throughout the kiln rather than just up at the front near the firebox. Mark and I took over whilst the brothers Browning-Howe went off to nap. We continued reducing for a few hours before opening the air up some and going for temperature gain.

Early glow from stoke hole 1.

Stoking wood prepared, resting on the kiln.

It took us a while to get the cones moving, but once we did the progress down the kiln was pretty fast. By midday we had a full team out helping. Joe Sink in the firebox, Matt Hallyburton and I side stoking one side, Mark and Stillman working the other. We had to be vigilant watching for sparks or lit leaves flying around as the wind was quite strong. Nothing calamitous happened but the conditions were potentially dangerous.

Joe stoking the firebox around midday.

Matt side stoking.
By 3pm we were salting the kiln, catapulting 150lbs of salt throughout the kiln with a leaf blower. By 4pm we were opening up the stoking holes to crash cool the beast and peek inside at the orange glowing pots. This crash cooling helps the glazes set and avoids any crystallization. By about 6pm we clammed up all the stoke holes and set to waiting.

Buckets of clamming (a mix of floor sweepings, clay, and sand) with which we seal the kiln.

Early on in the firing (top picture) and right at the end when we opened up to cool fast (bottom picture).

A week goes by whilst we bite our nails.

Here's a picture of the vegetable garden in the frosty early morning to provide a little pause here. Its not a great photo so you probably can't tell all thats in there: garlic, rapini, winter peas, buckwheat, rye, collards, sprouts, broccoli, cauliflower, beets, chard, lettuce, kale, tat-soi, turnips, carrots and I'm sure to be forgetting something.

The plastic sheeting is to cover tender buttercrunch and other greens from the frost.
Opening the kiln was a pleasure. We got it nice and hot, and reduced, front to back. The ash glazes came out deeper and more golden than I have seen in my year-and-a-half at the pottery so far. The EPK slip was dark and ate up the salt nicely, and we got lots of wood ash drips at the front. Our new glaze made from local granite was a bit of a mixed bag; it looks fantastic when really hot, but matte in cool spots. Now we know for the future and can pack accordingly. It was an excellent firing; Mark said it could be one of the best ever. So, like a vintage of wine, we shall remember 96 as one of the rather fine ones. Below are pictures of some of the pots on the first morning of the kiln opening. Enjoy.

Mark Hewitt 120lb planter, 2016. Close up of the ash glaze over incised floral decoration.

A few announcements before letting in the customers this morning.

The remaining big pots (some had already sold).

Big pot, Mark Hewitt. Ash glaze over manganese slip with glass drips.

Big pot, Mark Hewitt. Ash glaze over incised floral motifs, stamped neck, manganese slip finial.

Big pots, Mark Hewitt. Mixture of lilac slip and yellow glaze decorations.  

Close up of the neck on one of Mark's big pots; ash glaze with glass decoration.

Monster planter, Mark Hewitt. Manganese slip lines, white glaze dots, and glass runs.

Ash glaze 120lb planter, Mark Hewitt.

Considering a large platter. We fired these underneath the main stacks of pots: some got covered in ashes

These pots were simply slipped and accented with glass. The salty atmosphere of the kiln made them shine!

Close up of one of Mark's bowls: there is a really beautiful quality to this glaze.

One of Mark's ash glazed cereal bowls.

Sweet plate-- I like the drips peeking out over the rim.
Into the inner barn...

Mostly ash/alkaline glazed pots by Mark.

10 gallon vase, Mark Hewitt. Ash glaze over incised zigzagging lines, blue glass on shoulder, manganese slip neck.

Grave markers, Mark Hewitt.

Canister jar, Mark Hewitt. EPK slip.

Tankards (and pitcher), Mark Hewitt. Slip trailed decoration.

Cookie jar (7lb), Mark Hewitt. EPK slip.

Various of Mark's pots with our new local granite celadon.
And now some of mine and Stillman's pots...

A couple of shelves of my pots.

Tumblers. Stillman Browning-Howe. Slip trailed decoration.

Small 3/4lb cruet, Hamish Jackson. I am really into these; definitely have to make more next time. 

Spoon holders, Hamish Jackson. 

Teapot, Hamish Jackson. My first teapots at the Hewitt Pottery! My favorite things to make by far... so much to go wrong but I love them. Mark is very particular about them too: they have to be light with low bellies, high handles, and sharply upturned spouts.

Water (or beer) bottle. Hamish Jackson.

Cookie jar, Hamish Jackson. Black slip dimpled by heavy salting with blue glass drip.

Considering one of my tankards.

Tankard, Hamish Jackson. My first attempt at doing these curly handles -- quite fun.

One of my pitchers and a couple of mugs. I am not happy with the shape of any of these, really, but especially not the pitcher; it needs a fatter belly, and a tighter, longer neck.

Mixing bowl, Hamish Jackson. Slip trailed decoration.

Wall vases/pockets, Hamish Jackson. I like making these; especially as they remind me of bees.

Some of mine and Stilly's mixing bowls.

Bottle, Hamish Jackson. Nice firing on this bottle: plenty of salt and lots of wood ash collected on the shoulder which melted down.

Ginger jar, Stillman Browning-Howe. It was great watching Stilly get into making his first ginger jars; his enthusiasm is infectious. Some of them, like this one, came out really nicely.

Cookie jar, Hamish Jackson. This was glazed with our granite celadon + 1% ochre.

Flower pot, Hamish Jackson. Slip trailed decoration.

Much interest at this table -- some bargains to be had. 

Jar, Adrian King (former apprentice); still up for grabs!

Mark rockin' out in the kiln. We put a disco ball up for all those who needed a break from the riotous christmas shopping.

Nice chap clutching one of Stillman's jars and heading for the checkout (or the disco kiln?). 

This lady came prepared with not one but two baskets.

96 done.
 Roll on 97.

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Visit to Svend Bayer's Pottery in Sheepwash, Devon, England

It was a fine spring day in May when my wife Lauren and I visited Svend Bayer's pottery in Devon; the bluebells were in full force. Visiting Svend was a must on my trip to England. I knew of his work and that he had been one of Michael Cardew's apprentices, but Mark Hewitt's admiration convinced me that I needed to go.

Beginning in 1969, Svend spent three and a half years working with Cardew, and afterwards worked at Brannam's as a production thrower. Brannam's was earthenware pottery manufacturing mostly flower pots and pitchers at that time. In a conversation with Lucy Birtles (published in Ceramics Monthly, March 1995), Svend said this was valuable experience: "having to make 120 pots a day, all exactly the same, instead of the 20 I'd been used to making." Cardew famously said Svend was his best pupil and a "force of nature." Receiving such a stunning compliment from Cardew was uncommon.

In his time after working with Cardew, Svend's pots became simpler and less ornamented. Cardew said that form was of utmost importance: 90% of the success of a pot was its form. Despite this proclamation, Cardew still utilised many decorative techniques, just as I am being trained in at the Hewitt pottery. As Mark says, though, and as I have observed at kiln openings, often the decoration sells the pot despite the form (and as an apprentice, some of my forms don't hit the perfect pitch, so nice decoration is pretty important)!

Later in this post, I have photos of Svend's current work and a few examples of pots he made whilst apprenticing at Wenford Bridge. The primary difference is that his pots have moved away from the decorative techniques of Cardew. Svend mostly uses the wood firing process to decorate his pots, rather than techniques such as slip trailing, slip combing, or sgraffito. His pots have gained a simplicity and purity that is hard to express in words and without one of his pots in hand. Svend says: "shape and form are all-important. Kilns, glazes, decoration must never take over--they are only there to help." He goes on, "To me, throwing has always come first. Wood firing has occupied another pinnacle" (p. 49, Ceramics Monthly, March 1995). I think this is a large part of the power of Svend's pots: form resolutely comes first.

Visiting Svend's gallery was wonderful. The simplicity and economy of forms surprised me... he does not make a great variety of pots, but those he does make are very well made. They feel good, with a reassuring heaviness. His knobs, rims, and handles are all chunky; not just to be practical but also because they add to the generosity of the pots. His handles appear to truly grow out of the body of his pots, something I am always aiming for. The curves of his forms are deliberate yet dainty... satisfying to behold and to hold. His pots make you want to squeeze them. We could have spent our plane ticket home multiple times over if we had bought all the pots we wanted.

Svend has built, torn down, and rebuilt over twenty kilns on his property in Devon. Sometimes they only got fired once before being re-configured. He said he'd learnt something new every time he built and fired a new kiln. This is a level of commitment to wood firing that many potters do not possess. Most people build a kiln and work with it even if it doesn't fire quite right. The time, energy, and money to tear down a kiln and rebuild it is huge. Svend invests in this experience, just as he does in the protracted firings which give the pots their complex surfaces. Form comes first but firing is also crucial. His tremendously neat wood stacks represent his work ethic and methodology.

Without further ado, here are my snaps from the day:

Bluebells in the woods beside Svend's cottage.
Bluebells!
The first of Svend's current kilns.
Inside the kiln.
Wood to be cut.
Svend's other kiln.
View from the chimney.
Nice stack.
Love the stoke holes.
Pile of broken pots and test rings near the kiln shed.
Shells used to place pots on in the kiln.
Svend's large pots sitting out in the garden.
View from the other end.
Nice ash drips on this one
Close up of one of Svend's big jars.
Gnarly jar by Charles Bound.
Svend's cottage with a freshly thatched roof.
Svend and Lauren, humoring me for a photo.
In the workshop...

Big pots sitting out to dry in the middle of the workshop. If this was my studio I'm sure I would accidentally bash one of these. No doubt.
Pots glazed and ready to be fired.
Medium sized pots ready to be fired.
Handled bowls drying out. 
Upside down bowls drying out.
Bowls. Glazed inside only.
Slip decorated serving bowls.
Freshly handled pitchers.
The new clay Svend was trying out when we arrived.
One of Svend's kick wheels with two large balls of clay ready to be thrown.
Pitchers resting on another of Svend's kick wheels.
Postcards hanging up in Svend's studio.
One of Svend's sculptures in progress.
Honey jar.
Glazed vases ready for firing. Love the symmetry in this picture.
Closer view of one of Svend's unfired large pots.
Nice lug handles on these large jars. 
Significant handles.
Jugs from above. The ridges in the handles are obvious from this angle.

Into the gallery...
Vases. Svend Bayer.
Nice crackle glaze on this vase. Svend Bayer.
Large lidded jar. Svend Bayer.
I like the handles on this pot.
Rows of bowls and honey jars. I was quite tempted by the jars. I love the galleries on them.
Beautiful surface on this jar.
Jugs with just the inside glazed.
Nice fat jugs. Great big bellies and handles on these.
Vases fired on their sides, on shells.
Bowls with handles-fantastically ergonomic pots--holding them just makes you want to eat soup out of them or cereal or whatever. And to see them lined up on hooks in your kitchen. I may have to be making some based on this idea.

Closer pic of the handled bowls.
This was my favorite of Svend's handled bowls but unfortunately it was already sold.

So much going on in this surface.
Vase. Svend Bayer.
A few of Svend's flattened sculptures. Super dramatic fired surfaces.
Black teapot that nearly came home with us.
Beautiful big jar. It looked lovely illuminated by the light streaming in from the window.
Sweet little lidded bowl.
Plates and bowls.
Platter. Svend Bayer.
Pitcher. Svend Bayer.
Honey pot. Svend Bayer. This one nearly came home with us. Such a lovely shape.
Some of the sold wares, set to one side.
Teapots made by Svend during his apprenticeship with Michael Cardew.
Scraffito coffee pots (Wenford Bridge).
Lidded pot. Svend Bayer (Wenford Bridge).
Salt shaker with twist on lid. Svend Bayer (Wenford Bridge).
Sweet little jar. Svend Bayer (Wenford Bridge). 
Fish plate. Svend Bayer (Wenford Bridge). I love the jauntiness of their back bones. It almost looks like they've just been hooked! 
Classic slip trailed decoration. Svend Bayer (Wenford Bridge).
Baking dish. Svend Bayer (Wenford Bridge). I'm a sucker for this classic Cardew decoration.
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