From February 2 to June 11 the Honolulu Museum of Art has an excellent exhibit of mizusashi from the Carol and Jeffrey Horvitz Collection. I went to see it yesterday for the first time and will be sure to go back again. It's from one of the finest collections of contemporary Japanese ceramics and includes 16 pieces. I enjoyed getting to see them up close and spent over an hour with them. Some of them were especially powerful and I took quite a few photos of them. Still, it's hard to communicate their power through photos so I hope you'll be able to see the exhibit while it's still at the Museum of Art.
In January of 2014, I fired the gas kiln for the first time with Kenny Kicklighter. You can see my blog about that in the Archives in the right column ("First Time Firing the Gas Kiln"). At that point I thought I'd become part of the regular firing rotation but that didn't happen. My work schedule became more erratic and Kenny left the Hawaii Potters Guild shortly after that firing. In short, I never fired the kiln again until September of 2016. At that time my work schedule became more regular and I could carve out 3 hours to load the kiln and then a whole day to fire it. Since Kenny was no longer with the guild, I decided to ask Matt Kriegler to mentor me. We did two firings together before he moved to New Jersey and I'm grateful for all that he taught me. Since September, I've fired the gas kiln about 9 or 10 times and I've helped to load and unload the kiln for many other firings. I've been able to fire it so many times since we fire our kiln every week and our firing team is small right now. I've read alot about kilns and firing kilns, I've talked with people who are more experienced than me, tried to see and think clearly about the process and write down notes about it all. I've made mistakes and learned from them. What I've learned so far I'd like to share with you. Maybe it will help you, especially if you're starting to fire a gas kiln or even if you're just curious about how kilns work.
I'll start by saying that ceramics is not a single skill but a cluster of skills. These skills are essential to the process of making pots, but they are not related in any other way. Skill at forming pots has nothing to do with trimming pots or making glazes or decorating pots, and firing kilns is something totally different still. They are all part of the process, but each stands alone as its own skill. Below are some of my observations about the firing of kilns and how to become more skillful at doing it.
Let's look at the kiln first, in this case the kiln at HPG since that's the only one I'm familiar with. Our kiln looks relatively small, but you can get hundreds of pots into it by stacking them floor to ceiling. It's rectangular with an arched top and two Venturi burners at the bottom of one of the short sides. The inside is lined with firebricks which are made of refractive clay to withstand the heat. There is a layer of hard bricks surrounding the firebricks and a layer of ceramic fiber insulation on top of the arch. The whole kiln is held together with an external steel frame. A heavy metal door slides on a rail and the part that faces the kiln is covered with firebricks and insulation. Two bars are put in place outside of the door to keep it snug during the firing. This is a downdraft kiln which means the fire enters from the bottom, shoots up to the top of the kiln, comes back down to the bottom and then exits through two flues at the base of the kiln and up the chimney. These super-heated gases flow over the pots during their journey from bottom to top and back to the bottom again and not only heat up the ware but also carry out the work of reduction which we'll speak about later. When you're firing a kiln, one of the most important things you're doing is heating up the kiln itself. At first all of the heat is coming from the burning gas that's shooting into the kiln, but as the firing progresses and the kiln absorbs more heat energy, more and more heat is coming from the radiant energy being emitted from the kiln walls, the shelves, and the posts which surround the pots.
When this kiln was first built back in the 90's, apparently it wasn't firing well so HPG invited Nils Lou, a well-known authority on kilns, to come to Hawaii and see what the problem might be. When he inspected the kiln, he noticed right away that the flues were too large. Originally each of the openings were approximately 10" by 6" and Nils made them about 5" by 4". A less commodious opening might seem to restrict the flow of air, but its effect is just the opposite. It utilizes the Venturi effect which creates more draw which moves air more quickly out of the kiln and up the chimney. While Nils was here, he trained some of the firers, including Kenny Kicklighter, and people bought copies of his book: The Art of Firing. I have a copy now and have found it the best thing I've read about kilns and what actually happens in kilns during a firing. One of the most important adjustments Nils made in our kiln was to introduce a simple firebox. Rather than a solid wall of firebricks, Nils placed a single brick about 12 inches away from the burner and 4 inches from the wall. Originally he placed the brick parallel to the wall but we found it worked better for us if it was placed at a slight angle so some of the flame was directed toward the inside of the kiln and then the rest toward the back wall. At the back wall was a configuation of four bricks. Two of them stood next to each other with a gap between them and another brick sat on top. A fourth brick sat against the back wall at a 45 degree angle which directed the flame upward. The gap between the bricks could be made smaller or larger which would fine tune the amount of flame that would travel up to the top of the kiln and how much would be directed toward the bottom. I've experimented with different configurations of these bricks, both the single brick near the burner and the four bricks near the back wall. I'm still working on this since I only make a single change each firing and then note what effects take place. Moving any of these bricks even half an inch can make a substantial difference in the top getting hotter than the bottom or vice versa.
In my opinion, loading the kiln is the most important part of firing. I have a crew of two guys, Hitoshi and Nick, who help me load. Other people might join in on occasion, especially if they want something they made to get into the kiln, but more than three or four people (including me) starts to get a little crowded. Throughout the loading, at least one person is helping to organize pieces according to height. This has cut down our loading time by at least a third. So one person is organizing by height while another is handing me pieces to load. If I have a fourth person, all they do is organize groups of fillers, small pieces that we can tuck into gaps between pots. While Hitoshi and Nick are helping me, I'm showing them things so they can learn how to load and fire the kiln themselves. This is especially important since we're getting ready to install a second gas kiln which will be fired as soon as the first kiln is finished firing. That means we'll have at least two firings a week and will need double the number of people we presently have on our firing team.
In our kiln, we have three rectangular kiln shelves across the back, two square ones in front, and one layer of small rectangular shelves in the very front. That configuration has changed a bit over the years and probably will continue to change. I start with five-inch posts for all three courses of shelves, mainly because that's how tall the flues are and to allow air to flow easily into them. I put flatter pieces in several layers in the middle since the middle of our kiln tends to fire hotter than the rest of the kiln. My guess is that this slightly slows the flow of air through this section and decreases the temperature slightly in that area. I don't know if I'm right, but the middle doesn't seem to overheat as quickly anymore during my firings.
When I first started firing, everyone told me that the higher up in the kiln a piece was placed, the better the reduction. I wondered about that and came up with a slightly more nuanced understanding. I began placing small pieces of Rod's Bod on the inside and outside of each kiln shelf and found over several firings that reduction in our kiln depends on not just a piece's location from top to bottom but also from side to side. I like to picture it like a V. The lower in the kiln a piece is placed, the closer to the middle it should be placed in order to get good reduction. As you add shelves and move closer to the ceiling, the farther out toward the edge you can place pieces that need good reduction. My guess is that more highly oxygenated gases are found on the sides of the kiln where new air and gas are being introduced from the burners at the bottom and that gases become more heavily reduced as they move up the sides of the kiln. So on the lowest shelves I place pots as close to the middle as possible if they have glazes that need reduction and place pots that don't need as much reduction like Shino and Miller White on the outer edges. The higher up the stack goes, the farther out I can place pots that need reduction until I get near the top where I can put pots that need reduction all the way to the edge. The exceptions are the green celadons (Etsuko Green and Primavera Green) and Nelson's Transparent which are so sensitive that I never fire them lower than about a third of the way up the stack. If they're fired lower than that, they tend to come out brown, tan or some combination of green and brown.
Over time I've noticed that certain glazes do certain things in certain parts of the kiln. Some of that is based on studying pots when they're being unloaded and some is based on placing pieces with certain glazes in different parts of the kiln to see what happens. I know that glazes like Tenmoku will run off the pot if fired in certain parts of the kiln that are very hot, that Stoney Matt Blue will be a dry matt if placed in cooler parts of the kiln. I've had many glazes, especially matt glazes, that will develop a "sugary" surface from micro crystalline development if placed in the back top left. I place Oxblood on the top right front because I've had the most success firing it there. If Tenmoku is sprayed on porcelain thinly and placed on the top left shelf in the front, it will usually develop an unusual (and beautiful) rust color. I'm not saying any of these placements would work the same way in your kiln, but I'm suggesting you both keep your eyes open and do some systematic experimentation in order to discover how best to place your pots in the kiln to get the best results. I'll give you an example of one of my experiments. A fellow potter at HPG was making a series of jars using B-Mix and spraying on Plum Chun. Over the course of several firings, I placed her pots in different parts of the kiln until we came up with a result that pleased her. I almost wrote that "we came up with the result she was looking for," but when we started we weren't sure what the glaze might do and were only sure what we liked after seeing the results. In one part of the kiln the glaze was a matt lavender with very subtle variation in color; in another, the glaze looked good but almost always ran on to the kiln shelf. Finally we found a place where we were able to get consistent results that were to her liking: lavender with highlights where the blue glass matrix was exposed and tiny pink crystals were floating on top. I've also noticed that some of our iron yellow glazes (Butter Yellow and Stoneware Yellow) will turn glossy instead of matt in hotter parts of the kiln (not an effect I like) and will also turn much darker in color when overheated. This is true of many glazes. Longbeach Blue, for instance, develops a matt blue color that relies on a great deal of material not melting in the glaze. If too much melts under intense heat, the glaze becomes an olive color with brown highlights and patches of blue crystals. That looks good on some pots but I've thrown away plenty of these that looked awful.
I'm not going into the details of closing up the kiln, turning on the gas and lighting the burners, candling the kiln (if you do that), or using an oxygen probe and temperature gauge. Those things should be taught by a mentor and many of them are specific to each particular kiln. What I will mention next is what many potters call the three most important concepts to understand about how kilns work: temperature, atmosphere, and time. To be successful at firing kilns, you must understand how these three work together, especially since some of what you'll learn will not make sense at first.
Let's look at temperature first. All of us know that kilns have to get hot in order for clay and glazes to get hard and shiny. The way we get our kiln hot at HPG is through combustion, through introducing a certain amount of gas and air into the kiln through two Venturi burners. Before our kiln could be fired, wider diameter pipes had to be installed so more gas could flow to the burners. Not enough gas, not enough temperature. We call the burners "Venturi" after an Italian scientist who found that when liquid is flowing through a pipe or hose and becomes constricted, the flow slows down before the constriction but its velocity increases when exiting the constriction. Look at a Venturi burner and you'll see that it's the same size as your gas line where it connects with it, but then it narrows and then widens again at the burner head. If you look at the head of the burner, you'll notice that it curves slightly inward to create a more focused and hotter flame. If you didn't have these features, if you didn't have the constriction in the flow of gas that increases its velocity or the shaping of a hotter blue-white flame, you'd have a lazy orange/red flame that could never get the kiln up to temperature.
Getting the temperature of the kiln and the ware in the kiln up to more than 2300 degrees F is challenging. It took people many centuries to figure out how to heat clay up to stoneware temperatures or what people today call "cone 10." At first a firing is pretty straightforward: turn on the gas and watch the temperature steadily climb. But during the last 300 degrees or so, the kiln begins to do funny things. For instance, pressure builds up in the kiln as it gets hotter and that pressure makes it harder to introduce more heat. The kiln might "stall," which means the temperature moves up very slowly, stays at the same temperature, or even begins to drop. You might think that increasing the gas pressure will make the temperature rise more quickly but that will only make the problem worse. If you look at the logs at HPG that all the firers keep, you'll notice toward the end of each firing that most of them need to slightly increase the amount of air coming into the kiln and decrease the amount of gas. Increasing the air and decreasing the gas increases the efficiency of combustion and should help the temperature to rise again. So if the kiln begins to stall or the cones are going down faster on the bottom than the rest of the kiln, I'll open up the dampers a little and turn down the gas pressure from 11 to 10. In an hour I'll turn it down again to 9. I put this off as long as I can to make sure I get good reduction. As soon as I increase the air going into the kiln and reduce the gas, reduction goes down significantly. To check this, look at the flame coming out of the top peephole before you make these changes. If you're getting good reduction, the flame should be long, durable, and have a strong yellow/orange color. Then check it after you increase the air and decrease the gas. The flame should be short and retreat quickly into the kiln. There may be no flame at all. This means that reduction is no longer taking place in the kiln. This is okay if you're right at the end of the firing, the clay has vitrified and the glazes are melting. Reduction can't make much of a difference at this stage anyway.
Let me add one more important observation about introducing more air into the kiln by opening up the dampers. When you open the dampers, you're not letting more air in directly but indirectly. The dampers control the flow of gases out of the kiln and up the chimney, but by increasing the volume of gases that escape the kiln you increase the volume of new air that gets sucked into the kiln. All of this is related to the concept of "draw." Your chimney must be a certain height above the roof line in order for gases to circulate through the kiln and then be drawn or sucked up the chimney. If the chimney is not tall enough, your air circulation will be sluggish. If the chimney is shorter than the roof line of the building, the gases won't go up the chimney at all.
Now let's talk about "atmosphere," the second important concept to understand in order to grasp how kilns work. In general potters talk about two different kinds of atmospheres in the kiln: oxidation and reduction. An oxidyzing atmosphere is one in which combustion is complete. All of the gas is burned up and produces heat energy, carbon dioxide, nitrogen, and water vapor. An oxidyzing firing could be done in a gas kiln, but most are done now in electric kilns. A reduction atmosphere is created when too much gas and too little air is available for an efficient firing. A reduction firing by definition is the result of incomplete or inefficient combustion. Because there is too much gas and too little air, carbon monoxide is produced which seeks out another oxygen atom so it can become carbon dioxide. The long durable flame that comes out of the peephole shows the violence with which carbon monoxide seeks out that other oxygen atom. In the kiln, carbon monoxide penetrates the porous clay bodies in search of oxygen atoms. When the clay bodies vitrify, CO can no longer penetrate the body and reduction of the body diminishes or ceases altogether. At the same time, carbon monoxide is penetrating the glazes while they are still dusty on the pot's surface. When the glazes begin to melt, reduction diminishes or ceases altogether. That's why firing schedules will have places on them that say "Body Reduction" or "Glaze Reduction." Those temperatures don't mark when reduction begins but when you should start reduction before it's too late. Note too that the body begins to seal up before the glaze begins to melt. The reality is that both body and glaze reduction begin long before these temperatures that are listed on the firing schedule. Copper red glazes like Oxblood need a very long time for effective reduction to take place. When reduction takes place, the color of the glaze will change. A celadon like Etsuko Green will only become green if the copper oxide in it has been "reduced" by losing an oxygen atom to carbon monoxide. If it's not properly reduced, the glaze will be clear or tan. Oxblood, all the green celadons, CR-17, Nelson's Transparent, Chun, even Pete's Cranberry will all turn out clear or tan if not effectively reduced. All of these have copper or iron oxides that need a reduction atmosphere in order to become certain colors. Some people think that a smoky atmosphere is necessary to produce a reduction atmosphere. Nils Lou has a great section in his book on reduction and he explains that too much free carbon in the atmosphere will actually inhibit reduction. The key, I've found, is to create a reduction atmosphere no later than 1800 degrees and keep it above 55 or so on the oxygen probe for almost the rest of the firing. Also, as I wrote earlier, it's important to place pots in the kiln where they will get the most exposure to a reducing atmosphere. The temperature and atmosphere changes in different parts of the kiln. Even the way the kiln is loaded and the shelves are stacked effects the flow of gases and changes the temperature and atmosphere. Close observation and your own experiments can teach you the most about how your kiln works.
Time is the third part of the triad and the trickiest to understand. Temperature and atmosphere need adequate time to do their work inside the kiln. We have probes to measure temperature and atmosphere inside the kiln, but we need pyrometric cones to measure the effects of temperature over time. Cones tell us not what the temperature is inside the kiln but how much of that heat energy has been absorbed by our pots. Time plus temperature is often referred to as "heat work," the time it takes for the heat energy in the kiln to mature both clay and glazes. I like to explain it like this. If you heat your oven up to 350 degrees and then put a chicken inside to roast, you don't expect the chicken to absorb all of that heat immediately; you don't expect your chicken to have an internal temperature of 350 in five minutes. In fact, after an hour in the oven, your chicken will probably have an internal temperature of about 170 or so. Chickens aren't good conductors of heat and neither are pots. It takes a long time for them to absorb the heat energy that surrounds them in the oven or in the kiln. In fact, Orton makes it clear in its material that the quicker a kiln goes up in temperature, the higher the temperature in the kiln needs to be in order to reach cone 10. It takes time, lots of time for the clay and glazes to effectively absorb all of that energy.
I've been part of the ceramics programs at three different places, and I've come to appreciate the older and more inefficient kiln at HPG. Why is it so important for our kiln not to be too efficient? First, it takes quite a bit of time to vitrify clay and melt glazes. Time is especially important for the development of complex glaze effects. I've already mentioned reduction and want to reiterate that reduction can't be achieved in a few minutes or even a few hours. It takes time and that means the temperature shouldn't go up too fast. It also takes time for glazes to achieve greater melt. When glazes achieve greater melt, more material is available in the glass matrix to form crystals when the glaze begins cooling. I should add that it doesn't seem to make a difference if you move slowly or quickly up to about 1800 degrees F but the rate of temperature rise from there does seem to have a significant effect on glazes. The second reason why I think it's good that our kiln is inefficient is because it takes so long to cool down. Slow cooling is so important, especially if you can slow down the drop in temperature for the first several hundred degrees. This is when crystals form in your glazes. That's why glass is clear. It's cooled so quickly that crystals don't have time to form. If you want to see how slowly or quickly your kiln cools off, keep checking the probe every 15 minutes for an hour or two after you turn off the kiln. Check it again at 12 hours and 24 hours. I've compared that to the temperature drop after turning off an electric kiln, and the gas kiln cools down far more slowly.
In my experience, the same glazes often look quite different from one studio to another because of differences in the firing schedule. Two other studios where I've made pots seem most concerned with starting and finishing a firing as soon as possible, usually within three days. They pride themselves with "getting up to temperature" in record time so they can save money on gas and then cooling the kiln down quickly so they can get pots back to students as soon as possible. At HPG we start the kiln at night, come back 8 1/2 hours later, and then spend 10 to 12 hours finishing the firing. The kiln cools down for 4 days before it's unloaded. So we spend more money on our firings and we spend more time waiting for our pots, but it seems to be worth it. I've seen some of the same glazes at different studios and they often have a burnt look to them, or they might be a solid color but would have more variable effects because of crystal development after a firing at HPG. I understand that some people want a consistent color overall, but that's not what I find attractive. If you want more variation in your glazes, it takes time to achieve good reduction and good melt.
By the way, you may have wondered why cones have a numbering system that starts with cone 1 and goes all the way to cone 42 and then goes from 01 to 022. The Orton website (the major American manufacturer of pyrometric cones; www.ortonceramic.com) explains that when cones were first developed in the late 1800's, ceramics were fired in factories to at least 2000 degrees so cone 1 starts at about 2000 and cones go up from there at about 35 to 40 degree intervals. When people began developing better low-fire techniques at factories, Orton decided to use a zero rather than a minus sign to measure heat work intervals lower that cone 1. So the lower temperatures start with 01 and go down to 022.
Now I'll bring up a few issues in no particular order. First, find at least two people who want to become part of your loading crew. I asked Nick and Hitoshi to help me because I knew that both were interested in learning how to fire the kiln. They organize pots according to size and glazes so we can load more efficiently and get pots in the right places. They also keep an eye on things so I don't make major mistakes. Every time I put on a new shelf, for instance, one of them checks to see if we have sufficient clearance for the pieces on the shelves below. Kiln shelves get warped and can touch pieces that you thought were the right height. Sometimes they remind me that we need to put a cone pack on the next shelf so I don't use posts that are too short.
Second, decide whether or not you're going to use kiln wash or not. HPG uses kiln wash and every time we unload the kiln we examine every shelf to see if it needs to be sanded down and given a new coat. We set up a table and at least two people are busy grinding down pieces of clay and glazes left on the shelf and applying new kiln wash. The only problem with using kiln wash on shelves is that you can't flip them over for the next firing or bits of the kiln wash may fall into pots on the shelf below. When your shelves get too warped, they must be replaced. If you don't use kiln wash, you can flip them over each time and they stay relatively even. The disadvantage with this approach is that you must make sure they are kept meticulously clean. Even the smallest dot of glaze left on a kiln shelf will stick onto the foot of a pot and can chip it when it's removed, especially with porcelain which has a tendency to fracture. At one studio in Honolulu that doesn't use kiln wash, virtually every one of my pots comes out with chips on the feet since the shelves aren't kept clean.
Third, I like to do what other potters at HPG call a "soak" at the end of the firing. Actually it's not a soak since we don't maintain the same temperature for an hour but instead decrease the gas pressure which causes a slow decline in temperature. I didn't start out doing a soak because I wasn't taught that it was important. In time I ran into a few potters who told me they used an hour-long soak at the end of the firing to allow glazes to develop better crystals and for bubbles to heal over. What I've found over the last several firings is that when I turn the gas pressure down to 5 for 30 minutes and then down to 3 for 30 minutes, I don't end up with any bubbles in the bottom of my large bowls. Glazes like Oxblood bubble up alot and this longer soak helps those bubbles to settle down and for the glaze to even out. It also makes sense that it would favor greater crystal development and I've noticed that some of our matt glazes will become sugary with microcrystals forming during slow cooling near top temperature.
Fourth, keep a notebook just for the kiln that will include observations you want to make about each firing. I read these periodically or at least skim over them to remind myself of what I've seen so far. At the beginning, Matt Kriegler helped me write out a list of things to do to light the kiln and I go through this protocol step-by-step each time I start the kiln. I've received advice from more experienced firers and I write these things down and try them out if they seem to make sense. I might try a different configuration for my posts, or turn the gas up at certain times or close the dampers a bit based on their advice. I also study the logs that other firers have kept to get some idea how they did their firings. Anything I see that might help I add to my own technique.
Fifth, read as much as you can about kilns and how to fire them. The Art of Firing has taught me the most about firing a gas kiln but it's hard to find and expensive when you do. I've found some good resources on the internet, especially at places like The Big Ceramic Store (www.bigceramicstore.com). They have helpful technical articles scattered throughout the site. Books on glazes often have good information about firing kilns and I've learned a great deal from John Britt's book, The Complete Guide to High-Fire Glazes. He has two chapters in particular on "Measuring Heat" and "Kilns, Firing, and Safety" that are packed with important information. I read these sections each time I fire since I'm more focused then and since the ideas make more sense the more I fire the kiln.
Sixth, study the pots that are placed on the finished ware shelves. There is so much to learn from each pile of pots that's been freshly fired. I take my time with this, examining the glazes, see how different combinations worked or didn't work, how crystals formed, how thickness and thinness effect the glazes and how glazes interact with different clay bodies, On the day we unload the kiln, I always open the kiln door in the morning and spend at least 30 minutes or so unpacking the small stack of shelves at the very front. When the first stack is unloaded, I'll examine pots at the front of the first large stack and go through the same process of making mental and written notes of what I see. Several hours later, when the rest of the kiln is unloaded, it takes me about 45 minutes to unload hundreds of pots. Pots are flying out of the kiln so fast there's no time to examine each piece. I slow down a little if I see something extraordinary, but I can't do that much with 7 or 8 people waiting for me to hand them things.
Finally, let me talk about mistakes. I've made plenty of them and have had some very patient people working with me as I learned how to fire our kiln. Here are a few mistakes I've made which are chosen from a much longer list. I was loading the kiln and had gone up about six shelves when I noticed that the kiln post configuration that I was using was different than the configuration at the bottom of the kiln. I had to unload all of those shelves and start over. I was thankful for a patient loading crew! Another time my post configuration was wrong at the front of the kiln so that it would have been impossible to properly position my cone packs in front of the peep holes. Thankfully I caught this one after just a few shelves had been stacked. One time I put in a cone pack when I was using 3-inch posts. When I put on the shelf, it broke the cones! Another time I decided to try candling the kiln for an hour and kept the fire bricks out of the peep holes during that hour. After an hour I turned up the gas pressure and left for home to get some sleep. When I came back the next morning the peep holes were still wide open and the temperature wasn't close to what it normally would be, so I was at HPG until late that night. Well, those are a few of the major mistakes I've made while learning to fire the gas kiln. You'll make your mistakes as well, but I hope you won't let them discourage you too much. You'll be as careful as you can be but you'll still break some people's pots while loading, and you'll place pots too close to each other so they fuse together. Some people will be upset at you because you didn't load their pots in your firing or their pots didn't turn out the way they wanted them. It's all part of the process! So do your best and in time you'll become skilled at firing your gas kiln.
For several years I've been complaining that ceramic artists like Bernard Leach and Shoji Hamada have had more than their fair share of exhibitions and monographs but that Peter Voulkos, an artist of greater importance than the two of them put together, has been almost completely neglected. It's been at least 20 years since a major retrospective of his work has been mounted in the United States and the number of monographs on him are shockingly thin. That has begun to change with the recent exhibition of Voulkos: The Breakthrough Years at the Museum of Arts and Design in New York City. The exhibition focuses on the most influential years of Voulkos's work, 1953 to 1968, years in which Voulkos's experiments with clay convulsed the ceramic world. Leach and Hamada will always be important for their contribution to the birth of the studio pottery movement, but Voulkos took clay in a totally different direction and made it an accepted medium for artistic expression. If you're in New York, you can still see the exhibition until March 15. After that it will move to the Renwick Gallery in Washington, DC from April 7 through August 20. A major monograph has also been produced, Voulkos: The Breakthrough Years. For more information go to the following website: http://madmuseum.org/exhibition/voulkos.
Ceramics of Hawaii was the first state-wide exhibit at the Honolulu Museum of Art School that focused solely on ceramics. It was on display from December 17th 2016 to January 8th 2017. Artists from every island sent pieces to the gallery at Linekona for jurying. David Kurioka, a native of Kauai and a Professor of Art, Emeritus at the University of San Francisco, was the guest juror. David is an internationally recognized ceramic artist and has studios in both California and Hawaii. Over 400 pieces were submitted and David chose 90 for the exhibit. A section was reserved for "Pioneers," four potters who had an enormous impact on ceramic arts in Hawaii: Toshiko Takaezu, Harue McVay, Isami Enomoto, and Claude Horan. There were also displays around the gallery for each island that gave a brief history of how ceramic arts have developed there. The Hawaii Potters Guild organized this exhibit in part because many potters felt a show dedicated to ceramics was overdue and because HPG will be celebrating its 50th anniversary in 2017. The show received some media attention and attendance was good. Below are pictures of each piece in the exhibit along with a brief description.
In my last blog from November 28th, I wrote about making lots of cups in preparation for my first solo sale on December 10th. In this blog I'm concentrating on making bowls for the same sale. In my last blog I mentioned my struggles trying to center small pieces of clay when making cups and the same applies to making small bowls. I had to learn a new technique for centering and pulling walls in order to make small bowls that were acceptable to me. If you'd like to learn more about what I did to center smaller pieces of clay, check out my Nov. 28th blog.
I started throwing lots of smaller bowls beginning in September. My goal was to make at least 100 bowls and I reached that goal by December, but it was harder to get to than I realized it would be. My first small bowls were all thrown the same way I throw large bowls with thin walls that stretched out wide. These tended to warp quite a bit and I threw a bunch away. I also put too much glaze on lots of them (especially too much Turquoise Blue Matt), and I must have thrown away at least 10 to 15 of them that ran onto the shelf. I also tried several glazes and combinations of glazes that I didn't care for and many of these I donated or threw away. For instance, I glazed five bowls with Aka's Blue and hated every one of them. I donated them to Empty Bowl and said good riddance. Some firings were especially bad such as the one where I donated or threw away all four of the large bowls that were in the firing along with 15 cups and bowls that didn't turn out well. Always a long drive home after a firing like that, even if the drive only takes 7 minutes. And I was the one who did the firing!
At first I was making small bowls using the same technique I used for large bowls. With large bowls, I use two ribs to stretch the clay out as far as I can. With small bowls, this technique made the walls of the bowls too thin, too unstable, and they warped too much. Now I use my hands more on smaller bowls and use ribs only at the very end to give the bowl its final shape. I don't try to stretch the walls out too thinly and the form is more compact and the walls more vertical. I've had fewer problems with warping and the bowls don't tip over as easily. In my large bowls, the feet aren't usually well defined but simply curve down to the floor. Now on most of my small bowls I'm trimming a distinct foot and I think it usually looks better. The feet are also proportionately larger on my small bowls and I've made the feet as level as possible on the bottom to make them more stable.
I've tried different decorative schemes with these bowls and some have become favorites. One is a wax resist pattern on white clay that's either a simple vertical slash with the brush or an abstract tree and branches. The Turquoise Blue Matt that I pour on it has copper that fumes these waxed spaces and gives the raw clay a thin orange glaze. I also like brushing a wax resist pattern on dark clay and then pouring Longbeach Blue over it. Because the bowl is upside down when I'm pouring, the glaze pools at the bottom of each glazed spot and looks like it's thicker at the top when turned right side up. I also decided it was a good idea to wax the bottom of bowls if I was going to pour the glaze but it wasn't a good idea to wax the bottom if I'm going to spray. When I sprayed, the glaze would shed off the wax and leave thick globs of glaze on the edge of the wax. It was impossible to thin these out and make them blend in. It might take a little longer to clean off the foot if it's not waxed before spraying, but the glaze will be the same thickness all the way to the foot.
I also found it much easier to wax the outside of a bowl or cup if I'd just glazed the inside. If the bisqued clay is completely dry, it's tacky and absorbs water quickly. This can make it hard to brush wax on fluently. After glazing the inside of a bowl or cup, however, the wax brushes on more easily since the clay is saturated with water and is not as tacky.
Below are photos of most of the different types of bowls I've made since September. I'm showing them upside down as well since it's hard to see what the colors look like when they're right side up.
I've been making pottery for almost five years now, and I've made well over a thousand pieces. Most of those pieces have been large bowls and vases. With my first solo sale coming up on December 10th (see the blog below), I decided to focus more on small ware, especially cups and bowls. My family had been urging me for some time to begin making more small ware but I resisted because I didn't want to become a "production potter" making the same things over and over again. I loved making unique things. Another reason why I didn't make more small stuff was because I found it difficult to center small pieces of clay, especially when they were less than two pounds. But then I reread an interview with one of my favorite potters, Pierre Bayle, and he mentioned that he started out as a production potter making large garden pots. He hated making the same thing every day, so eventually he left, but that experience elevated his skills and made him a fluent thrower. For him, "technique must be controlled to the point where it can be forgotten," but he would still return each year to one of the factories for 10 days to throw large garden pots as beautifully as he could make them just to keep his skills up. I thought about that for awhile and decided that I wanted to see what it might be like to throw similar pots over and over again. Maybe that would make me a more fluent thrower as well. So around the beginning of September I began making lots of bowls and cups. I had a backlog of clay from the summer because we had moved from Kailua to Manoa at the end of May and I didn't make anything for more than two months because it took so long to get everything at the house in order. I also had lots of recycled clay that was sitting around that I hadn't touched since the spring. Most of it was pretty hard and I had to rehydrate it, not exactly my favorite thing to do especially since I'd already recycled it once. I decided to use most of my recycled clay, both dark and light, to make small bowls and cups. This blog will highlight some of what I've learned about making cups. The next blog will highlight what I've learned about making small bowls.
My first goal beginning in September was to come up with a more efficient way of centering small pieces of clay. I tried all sorts of different techniques but nothing seemed to work. My usual way of centering a larger piece of clay is to use my left hand as the steady hand and the right hand to push against it. That works fine with larger pieces of clay, but I had a hard time positioning my hands around smaller pieces of clay using that technique. I don't remember why, but I decided to center on the other side using my right hand as the steady hand and my left as the one pushing against it, and that was the key for me. Suddenly centering smaller pieces of clay became easy. Just one or two moves and the whole thing was centered. Another important change in my centering technique was using my little fingers on both hands to firmly come underneath the clay at the bottom to make sure that all of the clay was centered all the way to the bat.
My first cups were enormous, way too bulbous to get my hand around. I checked and these first cups held about 16 ounces of liquid! Most of those I ended up giving away. My cups have become smaller and more slender, but I needed to change my technique in several ways in order to accomplish this. First, I gradually learned how to throw smaller and smaller pieces of clay. At first my cups were a little too large because I was using a pound or more of clay. Eventually I learned how to throw three quarters of a pound and half a pound of clay. Second, my new throwing technique was making two small pulls using a sponge (which saved my fingers from being too abraded by the plastic bats) and then one long pull using only my fingers. By not making the walls come up too high at the beginning, it allowed me to reach down to the bottom for the last pull with fewer fingers so I didn't push out the sides too far. That had been the problem with the first cups I'd made. When I made my final pull my walls would already be so high I'd have to stick my entire hand into the cup to get my fingers to the bottom and it would push the walls out too far. The walls by that time were so thin that I couldn't get them to come in again.
I tried several designs and am still in the process of evaluating them. I've had family and friends over several times and have used these cups as part of our table settings. I've asked them to try different cups and tell me their preferences both in design and decoration. Most seem to like a glossier glaze since it feels smoother and less tacky on the lips. They also like rims that are thinner and curve out a bit rather than curving in. The rim is always a challenge for me since most people like thinner rims but they also chip more easily. The feet of my cups are also getting smaller, something people always comment on. If the bottoms are made as level as possible, these cups are very steady. However, I get comments like this from people at HPG fairly frequently: "I couldn't use one of your cups. They make me too nervous. I get nervous just looking at them." Usually I just laugh when people say such things, but if I'm feeling sassy I'll say "Well, these cups are for adults. Whatever you do, don't let children use them!" People will also comment about how the cups don't have handles. When they ask, "Why don't you put handles on your cups," I'll just answer "Because I don't want to." I suppose that's how you lose sales but I don't care. That's one nice thing about not earning your living as a potter. Of course, give me six more months and I'll start making mugs with handles!
I've also tried several ways of decorating the cups, as you can see below. It's always interesting to see how glazes respond to dark or white clay bodies. I'm also very interested in the look of my recycled clay and trying to expose it as much as possible. Quite a few people have commented on how much they like the look and feel of the bare clay that's been sanded smooth. What lots of people like, and what you won't see on any other clay body that I know of, is a speckled look from different colors of grog. My white recycled clay always has some dark clay in it and vice versa. What that means is that some dark grog ends up as black speckles in my white recycled and some white grog ends up as white speckles in my dark recycled. It looks great but is hard to show in a photograph, at least with my camera. Most of these cups are glazed on the inside with Miller White, a food-safe glaze. I've been having trouble with it developing bubbles, however, and have refired several pieces or even thrown them away. I'm beginning to use Glossy White and Nelson's Transparent, both food-safe, as alternative liners and have found both work well. I also used a different technique when glazing the cups. I poured the glaze through a sieve into a plastic pitcher. I poured it about two thirds of the way up since the glaze will flow over the top of the rim if it starts out too high. Something called "displacement" if I remember correctly. So I would wet the bottom inch of the cup that wasn't going to be glazed anyway so I could grasp it more securely. The bisqued clay is tacky when wet which helps you hang on to the cup when dipping it in the glaze. With some glazes, especially with dark clay, I would dip it twice, but most of the time I was just holding it submerged in the glaze for several seconds before lifting it out.
Below are examples of most of the different designs and glazing effects that I've tried on my cups since September. I hope they'll give you some ideas about how to make your own cups.
A few months ago I began thinking about having my first solo pottery sale. I wanted to have it at my house but it's on Oahu Ave. which doesn't have any street parking. One of my friends heard I was looking for a venue for my sale and offered to have it at his house. So, I'll be having a sale of my pottery on Saturday, December 10th, from 9am to 2pm. My friend's house is located at 2123 Hunnewell St. in Manoa. If you're in Australia this may be a bit of a drive, but if you're on Oahu I hope to see you at the sale. I've been busy making lots of pots. Many of them are the larger pieces that I usually make, but over the last few months I've been making small bowls and cups and other functional pieces. I'm trying out different designs and glazes, so you can let me know what especially appeals to you. The cups are between $20 and $25 and the bowls are between $25 and $30. Hopefully you can find something to use at home or give as gifts to family and friends. I'm trying to make the sort of bowl or cup that you always look for when you open the cupboard. Below is a link to photos of some pieces I'll have at the sale. I'm also thinking about offering prints of some of my photos so we may have a table for that as well. When you purchase something you can pay either with cash or with a credit card. If you have any questions, please let me know. Hope to see you on December 10th! https://1drv.ms/a/s!AitkLRyx794Wk0N3MPzonpAS9wql
On Tuesday, October 25, Hawai'i Craftsmen opened its 49th Statewide Juried Exhibition. There were almost 300 submissions from five islands in a variety of media such as wood, jewelry, metalwork, fiber, and glass, but ceramics was the most popular medium, an indication of the large and growing clay community in Hawai'i. The juror this year was Cindi Strauss, Sara and Bill Morgan Curator of Decorative Arts, Craft, and Design and Assistant Director, Programing, at The Museum of Fine Arts, Houston. In her Juror Statement she mentioned that jurying a show this broad is "simultaneously exhausting and exhilarating" and that exhibitions such as this one "demonstrate that the craft field is alive and well in all parts of America." Jurying this show is especially challenging since the juror must travel from island to island to see the work of the artists living there and pick out pieces for the exhibition. She also gave a public lecture at each stop and you can imagine how tired she might have been when her lecture began at 5 in the afternoon but it felt like 10 back in Houston. We appreciate her perseverance and having such a great attitude during the whole process. To show you how much pressure she was under, during the final jurying in Honolulu she evaluated about 200 pieces in 3 hours. Mahalo nui loa to Cindi for hanging in there and putting together such a great exhibition!
The exhibition was well designed and we owe kudos to Dr. Barbara Thompson (Vice President of Hawai'i Craftsmen and an experienced curator), Jackie Mild Lau and Chris Edwards. As in the past, the selection of ceramics was especially strong. Daven Hee, one of my teachers and one of the best ceramicists in the state, was an invited artist this year. His exhibition of four clay toys included a truck, a car, a spaceship, and a toy box. As of this writing, two of the pieces have sold, one to the Honolulu Museum of Art. I have three pieces in the show, including one that won the Merit Award in Ceramics Arts so I feel pretty lucky. I suppose I should feel proud about the award but opening night I felt more sheepish than anything since I couldn't help comparing my piece to others and wondering how I won.
Amber Aguirre won the highest award in the show, the Award of Excellence in Honor of Charles E. Higa, for her ceramic sculpture entitled Disabled. I saw her at the reception and noticed she had a medical boot on her left leg and was walking with a cane. Both of her pieces in the show dealt with themes about illness and she told me she'd been in and out of the hospital because of complications with surgery on her leg and was still doing physical therapy twice a day. Her struggles with illness and pain were reflected in her art. My conversation with her made me think about how many artists use their art to work out personal issues. I took a course with Joey Chiarello this past spring and he told me he used his clay work to literally work out his demons or at least start some type of rapprochement. Every demon he makes is a self portrait, something I hadn't noticed until he pointed it out to me. Maybe I like my designs to be more controlled because so many parts of my life feel like they're out of my control!
Below you'll find photos of all the ceramics in the exhibition. If you're in the Honolulu area, I hope you'll stop by the gallery at the Honolulu Museum of Art School at Linekona. It will be up until November 13. It's closed on Mondays but is open Tuesday through Saturday from 10:00 to 4:30 and Sunday from 1:00 to 5:00.
I just completed my first pit firing at home. Before this I'd always pit fired with my friends at Steve Martin's place in Kaneohe. I want to continue firing with them, but the firings are so infrequent that I needed to set things up to fire at home. I just moved from Kailua to Manoa so I'm officially a "townie" now. I miss the Windward Side of Oahu because I lived there for 24 years, but I like where we're at now. There's about an eight foot wall on one side of the house with a twelve foot wide alley covered in gravel, perfect for setting up a fire pit. At least that's what I thought until I lit the fire and smoke started billowing into the sky. Every time I heard a truck pass by I thought it was a fire truck with a police cruiser just behind it. I kept thinking about what I'd say while the police officer was writing out the citation. As it turned out, no one called the fire department, not this time anyway.
To prepare for pit firing at home, I'd ordered a Behrens 17 gallon round steel tub from Amazon which seemed about the right size for my needs. Maybe I'll get a larger one later or pick up a 55 gallon drum that's been cut in half, but I can fire at least two large pots in it or three medium size ones. I could get more in if I decided to stack pots, something I plan on doing sometime soon. I found a reliable source for Kiawe wood at Hardware Hawaii in Kailua and spent about $12 on this firing. The pieces of wood were too large so I used my machete to split them into smaller pieces. That's something I've learned after several pit firings: the wood needs to be cut pretty small for the fire to really get hot. I had to use large pieces of wood for almost every pit firing up to now and it took forever to get the fire going, it never got hot enough to give all of the pots really good color, and I breathed in too many noxious fumes leaning over the pit with my blow torch. I also thought it would be good to use small pieces of wood after watching a video about wood firing in Onda Japan. They use very thin pieces of wood when they want the temperature of the fire to go up quickly. I'm not afraid of making the fire go up quickly in the pit since I'm using clay bodies (B-Mix with Grog or Nash White) which have proven their ability to withstand thermal shock doing raku.
The wood shavings I use at the bottom of the pit are intended for horse bedding so fairly coarse. I've seen people use fine wood shavings that were almost like sawdust but the results have never been very good. The shavings are so dense that it's hard for air to get into them so they don't burn all the way to the bottom. By the way, try using the metal basket of an old washing machine for pit firing. Steve Martin uses one and it always gets great results for small to medium size pieces. The basket has perforations all the way around that are small enough to keep the wood shavings in but large enough to allow air to circulate through on every side from top to bottom.
I laid my two pots on the wood shavings and then laid around them the usual things I use to make marks on the pots: salt, copper carbonate, red iron oxide, banana peels, coffee grounds, and seaweed. I pulled apart both fine and coarse steel wool and laid that lightly on top of both pots. Next I put on layers of newspaper, then a layer of drift wood, and finally kiawe wood. I used a blow torch to start the fire rather than using lighter fluid. I think next time I'll use lighter fluid since this time I got the torch too close to one of the pots for too long which may have caused the terra sig to peel in that area. The fire got going much more quickly than it usually does because everything was dry and smaller in size. I also fanned the flames fairly often during the first hour to really get the temperature up. I hadn't been satisfied with the results I'd been getting the last several times and grew more convinced it had to do with temperature. I'm not sure how hot the fire became, but it was much hotter than usual. Because the fire burned hotter, it consumed all of the fuel more quickly which meant it cooled down more quickly. Rather than the usual six or seven hours, this firing took only four hours from set up to pulling the pots out with oven mitts. There are several things I noticed about the results from this pit firing. Probably the most important is that higher temperatures seem to have a profound effect on the surface decoration of the pots. More color gets on the pots and the colors are deeper, more saturated. Color also seems to be driven farther into the pot so you get a layered look, almost three dimensional. If you look at the closeups below I think you can see what I mean. Instead of the color sitting on the surface, both the colors and the spots seem to be at different levels. All of these marks and color also seem softer at the edges and often will bleed into each other. You see more interesting shapes, and shapes within shapes as your eye moves across the pot. And I like having large areas that are lighter in color. I think it provides a more dramatic contrast than if everything is covered in peaches and burgundies. In short, everything seems more complex and I think that's a good thing.
Update on 9/28/16 I just completed my second firing at home. This time I used smaller pieces of kiawe that I bought at Safeway, a local grocery store, in order to get the fire started more quickly. Everything else was the same. It still took longer to get the fire started than I thought it should so I'm going to see if I can find small pieces of pine rather than hardwoods like kiawe that will burn more quickly.
I tried to make this firing as hot as I could, not at the very beginning of course, but as the fire became progressively hotter and the pots had time to heat up. I used a large box that was flattened that seemed to work well for fanning the flames. At one point I probably went a little too far and I heard a distinct pop and noticed a long crack running along the base of one of the pots. I guess it's really not watertight now! After about 3 or 4 hours, when the pots were almost done, it started raining and I decided to get the pots out of the fire pit. I use two long sturdy dowels to get the pots out by inserting one inside and using the other to steady it. I've had much greater success with this than with using raku tongs. I've seen too many people break the rims of their pots when inserting the tongs inside, and I haven't been able to get some pots out at all if they were too big around and had mouths that were too small. When I removed them from the pit, I rubbed ash on the smallest pot which made marks on it from the carbon that did not wash off (see photos). One of the pots was in the rain for a moment before I moved it inside and the raindrops made permanent marks on it (see photos).
I learned a great deal from this firing. Two of the three pieces were refired because I had been dissatisfied with how they had turned out when I fired them at Steve Martin's place about a month or so ago. The first firing didn't get hot enough and the pots turned out very dark, mostly a smoke firing. In this second firing, most of the carbon from the first firing seems to have burned off but not all of it. If I'm looking at this correctly, most of the color from the first firing seems to have remained on the pots, especially the reds. The second firing just added more color and more depth. I checked this with another pot that had been pit fired at Steve's that I put into a bisque firing (cone 06- 1828 F) in preparation for a regular glaze firing. All of the carbon burned off, but the reds from copper remained. It should be noted that this pot had not been coated with terra sig, so I'm still not sure if any color would remain on a pot with terra sig.
One of the pots that was refired had a texture created with a blue Mason stain slip with sodium silicate in it. I didn't put terra sig on it just to see what would happen. My impression after this second firing is that it absorbed an enormous amount of copper so it had more red on the pot than I usually get. I'm guessing that the more porous surface of the pot was able to absorb more from the fire. At the same time, the color is dry and doesn't appeal to me at all. The color doesn't have any depth and it's completely missing all of the little black spots that I love so much.
I spoke with a few potters since then about how they pit fire, and I received some advice that I'll try. One potter brought up an interesting issue. He said that he always uses a hole in the ground at his house when pit firing and encouraged me to do the same. He said that you need the ground to provide insulation so more heat would be retained and so the pots would cool more slowly when you were done. That made me think alot about what's happening in pit firing and how that might contrast with a cone 10 glaze firing. One of the most important concepts in glaze firing is the whole idea of "heat work." Heat work is the necessary combination of time and temperature when firing ceramics. If you throw a turkey into a 350 degree oven, you don't expect it to be 350 degrees in 5 minutes. Turkey is a poor conductor of heat so you might leave it in the oven for 3 or 4 hours until its internal temperature gets to around half that amount. Heat work is important for both clay bodies and glazes. It takes time for bodies and glazes to absorb heat and to vitrify or melt no matter how hot the kiln might be. But does this apply in the same way to pit firing? Since we're not using glazes, it certainly doesn't in some senses. But I've noticed that higher temperatures seem to volatilize colorants better and drive the color deeper into the pot, so heat is certainly important. Clay bodies also must be tolerant of thermal shock because temperatures are rising quite rapidly and they can fall precipitously is you pull pots from the pit fire when they're still really hot. I've done this many times and the only times I've had problems with this were with bowls. I have to keep bowls in the pit until they're completely cool or they will crack. My bowls, at least, can't withstand the stresses of being pulled out of the fire and placed on a piece of wood or concrete or metal. I'm intrigued by one thing, however, and that's the notion that pit fires can get much hotter if they have greater insulation. One potter claimed that his pit fires would get up to cone 06 (1828 F). I didn't ask how he verified that, but I should. I've never seen anyone using a pyrometer to measure how hot a particular pit firing gets, but I'm sure it's been done and could be done by me. Still, it's intriguing to think of what might happen at temperatures that high. Most books I read state that pit fires get up to around 1500 F at the most. Terra sig is also supposed to lose its sheen at temperatures that high. I'm also wondering how quickly color is added to a pot and how long a firing has to be sustained at a high temperature in order to get good color on a pot using this technique. In other words, does heat work play only a minor role in pit firing or does it potentially have more to contribute? Related to this, I'm interested in trying some saggar firing in our kiln to see what higher temperatures over longer periods of time might do using the same colorants. Maybe I'll try putting fire bricks around my pit or some type of ceramic fiber insulation. I can't dig a hole at the house where I'm renting, but maybe I could try it at Steve's place the next time we fire. And bring a pyrometer, of course!
Last night we celebrated the opening of two ceramics shows in Honolulu. The first is at the Louis Pohl Gallery and the second is at the Arts at Marks Garage, both located about a block away from each other in Chinatown. The sale at Louis Pohl Gallery has the theme "Whimsical Gardens" and has work related to flowers, plants, etc. I'm a part of this exhibition with four other potters. Thanks to Karen Kim for inviting me to be a part of the show. I don't really have very many pieces that relate directly to gardens but I have plenty of pieces that have organic forms and might be flower-like in their glazing. The show at Marks Garage has "Dinner Party" as its theme so the whole interior is made up like a cafe. There's even a menu that lists all of the pots and their prices. Daven Hee headed up the exhibition and did a great job of making it creative and fun. Both opened last night as a part of First Friday and were packed with people. The exhibit at Louis Pohl Gallery will be up through September 30th and the exhibit at Marks Garage goes through October 1st. Oh, and Tom Gibson has a great display of his tripod sculptures in the window at Marks Garage. Every time I see them I think of The White Mountains trilogy that I read as a kid.
I began potting in January of 2012. Because I'm so new to potting, I think I understand the challenges of beginning potters and hope this blog will be encouraging to them and a source of helpful information and comment. I hope you'll join the conversation!